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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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32 pages, 1679 KiB  
Review
Fungi and Actinobacteria: Alternative Probiotics for Sustainable Aquaculture
by Koushik Ghosh, Ramasamy Harikrishnan, Abhisek Mukhopadhyay and Einar Ringø
Fishes 2023, 8(12), 575; https://doi.org/10.3390/fishes8120575 - 25 Nov 2023
Cited by 15 | Viewed by 4678
Abstract
Aquatic animals are continually being exposed to stressors under farming conditions, increasing risks to gut health that result in dysbiosis. Since restrictions are imposed on the frequent use of antibiotics in aquaculture, there is emerging demand for economically viable, environmentally safe, and sustainable [...] Read more.
Aquatic animals are continually being exposed to stressors under farming conditions, increasing risks to gut health that result in dysbiosis. Since restrictions are imposed on the frequent use of antibiotics in aquaculture, there is emerging demand for economically viable, environmentally safe, and sustainable alternatives for the intensive production of aquaculture species. The application of beneficial microorganisms as probiotics has been suggested and widely practiced in recent times. Bacteria and fungi are ubiquitous microorganisms that can grow in various environments where organic substrates are available. Being rich in nutrients, a fish’s aquatic environment and gastrointestinal tract confer a favorable culture milieu for the microorganisms. However, the colonization and probiotic potential of fungi and mycelial bacteria resembling fungi (actinobacteria), either in the culture environment or within the gastrointestinal tracts of fish, have received less emphasis. Apart from bacilli and lactic acid bacteria, as the most conventionally used probiotics in aquaculture, numerous studies have focused on other promising alternatives. Diverse species of yeasts and molds belonging to the kingdom ‘Fungi’ have been characterized for their prospective roles in nutrition, immunomodulation, and disease prevention in fish. Bioactive compounds such as manno-oligosaccharides and β-glucans are recognized as fungal postbiotics that improve innate immunity and disease resistance in fish. Actinobacteria are known to possess different hydrolytic enzymes and novel secondary metabolites representing their probiotic attributes. The application of these groups in water quality amelioration has also been explored. Thus, this paper presents an overview of the present status of knowledge pertaining to the effects of yeasts (Candida, Cryptococcus, Debaryomyces, Geotrichum, Leucosporidium, Pichia, Rhodosporidium, Rhodotorula, Saccharomyces, Sporidiobolus, Sporobolomyces, Trichosporon and Yarrowialipolytica), molds (Aspergillus spp.) and actinobacteria (Streptomyces) as probiotics in finfish aquaculture, as well as their occurrence within the gastrointestinal tracts of finfish. Furthermore, probiotic mechanisms, selection criteria, and future perspectives on using fungi and actinobacteria as promising probiotics are discussed. Full article
(This article belongs to the Section Sustainable Aquaculture)
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14 pages, 2085 KiB  
Article
Growth Performance, Feed Utilisation, Digestive and Metabolic Enzyme Activity, and Liver Morphohistology in Hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus) Juveniles Fed with the Inclusion of Chitosan in Their Diet
by Yuniel Méndez-Martínez, Alan Rodrigo Vera-Veliz, Edilmar Cortés-Jacinto, Yanis Cruz-Quintana, Aroldo Botello-Leon, Pedro Daniel Mendoza-Carranza and Natalia S. Calvo
Fishes 2023, 8(11), 546; https://doi.org/10.3390/fishes8110546 - 9 Nov 2023
Cited by 9 | Viewed by 2828
Abstract
This study aimed to evaluate the growth performance, feed utilisation, digestive and metabolic enzyme activity, and liver histology in juveniles of hybrid red tilapia (Oreochromis mossambicus × Oreochromis niloticus) fed with the inclusion of chitosan in their diet. Six dietary chitosan [...] Read more.
This study aimed to evaluate the growth performance, feed utilisation, digestive and metabolic enzyme activity, and liver histology in juveniles of hybrid red tilapia (Oreochromis mossambicus × Oreochromis niloticus) fed with the inclusion of chitosan in their diet. Six dietary chitosan levels (0 “control’’, 10, 20, 30, 40, and 50 g kg−1) were used to feed juvenile fish (initial weight 7.50 ± 0.20 g) that were cultured for eight weeks in 18 tanks at a density of 15 fish/tank. The growth performance presented significant differences (p ˂ 0.05) for weight gain, specific growth rate, feed conversion ratio, hepatosomatic index, and survival rate. The digestive and metabolic enzyme activities were significantly (p < 0.05) influenced by the levels of chitosan in the administered diet. Histologically, no damage was found in the liver; however, morphometrically, a significant difference (p < 0.05) was found in the hepatocyte area and sinusoid area. Vacuolisation of hepatocytes was found in treatments with 40 and 50 g kg−1 of chitosan in the diet. Treatments with doses of chitosan showed a better response (p < 0.05) compared to the control treatment in most of the different groups of variables analysed. The result of the principal component analysis suggests that a diet containing 40 g kg−1 of chitosan is optimal for tilapia growth performance. Full article
(This article belongs to the Special Issue Feed Additives in Aquaculture)
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18 pages, 1667 KiB  
Article
The Effect of Dietary Lipid Supplementation on the Serum Biochemistry, Antioxidant Responses, Initial Immunity, and mTOR Pathway of Juvenile Tilapia (Oreochromis niloticus)
by Yongqiang Liu, Enhao Huang, Yi Xie, Liuqing Meng, Dongsheng Liu, Ziqi Zhang, Jiang Zhou, Qin Zhang and Tong Tong
Fishes 2023, 8(11), 535; https://doi.org/10.3390/fishes8110535 - 26 Oct 2023
Cited by 11 | Viewed by 2270
Abstract
The objectives of this study were to investigate the effect of different dietary lipid levels on the serum biochemistry, antioxidant responses, initial immunity, and mTOR pathway of juvenile genetic improvement-farmed tilapia (GIFT, Oreochromis niloticus). Six groups of the juveniles (initial body weight [...] Read more.
The objectives of this study were to investigate the effect of different dietary lipid levels on the serum biochemistry, antioxidant responses, initial immunity, and mTOR pathway of juvenile genetic improvement-farmed tilapia (GIFT, Oreochromis niloticus). Six groups of the juveniles (initial body weight 20.66 ± 1.33 g) in triplicate were fed for 90 days using six iso-nitrogen diets with different lipid levels (0.35%, 3.35%, 6.35%, 9.35%, 12.35%, and 15.35%). The main results were as follows: Compared with the control group (0.35%), the diets with different lipid supplementation significantly improved (p < 0.05) the contents of total protein (TP), albumin (ALB), globulin (GLB), glucose (GLU), triglyceride (TG), total cholesterol (T-CHO), high-density lipoprotein (HDL), low-density lipoprotein (LDL), total antioxidant capacity (T-AOC), malondialdehyde (MDA), complement 3 (C3), and immunoglobulin M (IgM), the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), lysozyme (LYZ), and alkaline phosphatase (ALP), the expression level of phosphatidylinositol-3-kinase (PI3K), Akt protein kinase B (Akt), and mammalian target of rapamycin (mTOR) genes in juvenile tilapia. However, diets with different lipid supplementation significantly reduced (p < 0.05) the expression level of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) genes of juvenile tilapia. In conclusion, the with different lipid supplementation could significantly affect the serum biochemistry, antioxidant responses, initial immunity, and mTOR pathway of juvenile tilapia. Full article
(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)
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17 pages, 38616 KiB  
Article
An Improved Deep Learning Model for Underwater Species Recognition in Aquaculture
by Mahdi Hamzaoui, Mohamed Ould-Elhassen Aoueileyine, Lamia Romdhani and Ridha Bouallegue
Fishes 2023, 8(10), 514; https://doi.org/10.3390/fishes8100514 - 16 Oct 2023
Cited by 16 | Viewed by 6501
Abstract
The ability to differentiate between various fish species plays an essential role in aquaculture. It helps to protect their populations and monitor their health situations and their nutrient systems. However, old machine learning methods are unable to detect objects in images with complex [...] Read more.
The ability to differentiate between various fish species plays an essential role in aquaculture. It helps to protect their populations and monitor their health situations and their nutrient systems. However, old machine learning methods are unable to detect objects in images with complex backgrounds and especially in low-light conditions. This paper aims to improve the performance of a YOLO v5 model for fish recognition and classification. In the context of transfer learning, our improved model FishDETECT uses the pre-trained FishMask model. Then it is tested in various complex scenes. The experimental results show that FishDETECT is more effective than a simple YOLO v5 model. Using the evaluation metrics Precision, Recall, and mAP50, our new model achieved accuracy rates of 0.962, 0.978, and 0.995, respectively. Full article
(This article belongs to the Special Issue AI and Fisheries)
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13 pages, 886 KiB  
Article
The Effects of Different Carbon Sources on Water Quality, Growth Performance, Hematology, Immune, and Antioxidant Status in Cultured Nile Tilapia with Biofloc Technology
by Khalid Hussain Rind, Syed Sikandar Habib, Javed Ahmed Ujan, Francesco Fazio, Saira Naz, Aima Iram Batool, Mujeeb Ullah, Sobia Attaullah, Khayyam Khayyam and Khalid Khan
Fishes 2023, 8(10), 512; https://doi.org/10.3390/fishes8100512 - 14 Oct 2023
Cited by 17 | Viewed by 3946
Abstract
The biofloc technology system (BFT) is considered to be one of the sustainable aquaculture systems, which is based on the principle of nutrient recycling with the addition of a carbon source to give dominance to heterotrophic microorganisms. The objective of this study was [...] Read more.
The biofloc technology system (BFT) is considered to be one of the sustainable aquaculture systems, which is based on the principle of nutrient recycling with the addition of a carbon source to give dominance to heterotrophic microorganisms. The objective of this study was to evaluate the effect of sugar cane molasses and tapioca flour as carbon sources on the water quality, growth, hematology, immune status, and non-specific antioxidant status of Oreochromis juveniles. Methodologically, the experiment was carried out for 10 weeks on 225 juvenile Nile tilapia with initial body weights of 47.0 ± 1.3 g that were randomly distributed in 09 tanks (1000 L) with a stocking density of 25 tilapias per tank; the treatments were: BFT + SM (S molasses), BFT + TF tapioca flour (TF), and a control with no carbon source added. The control group was fed 100% feed, while the BFT experimental groups were fed microbial flocs along with 75% feed. The results revealed that the water quality parameters were affected by the carbon sources, but were adequate for normal fish welfare, and the biofloc volume was higher (28.94) with the TF carbon source. The growth performance, such as weight gain (98.61), survival (99.01), and improved feed conversion ratio (FCR) (1.69), was recorded in BFT + TF. Significant improvements in WBCs, HCT, HB, lymphocytes, plasma proteins, albumin, and non-specific immune factors (lysozyme activity, immunoglobulins levels, and ACH50) were observed in biofloc-reared fish with tapioca flour as the carbon source compared to the control and sugarcane molasses groups. Moreover, significant increases in catalase (CAT) and superoxide dismutase (SOD) were found in the biofloc-reared fish with different carbon sources. In conclusion, the use of BFT + TF was found to affect improving the water quality, growth, hematology, immunity, and antioxidant status of juvenile Tilapia. Full article
(This article belongs to the Special Issue Integrated Aquaculture and Monoculture of Low-Trophic Species)
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14 pages, 694 KiB  
Review
The Riddle of How Fisheries Influence Genetic Diversity
by Daniel E. Sadler, Phillip C. Watts and Silva Uusi-Heikkilä
Fishes 2023, 8(10), 510; https://doi.org/10.3390/fishes8100510 - 13 Oct 2023
Cited by 9 | Viewed by 5641
Abstract
Overfishing drives population decline, which in turn drives loss of genetic diversity. Many studies provide evidence of declines in genetic diversity; however, controversy exists within the literature, as some studies show evidence of no change in genetic diversity despite decades of overharvesting. The [...] Read more.
Overfishing drives population decline, which in turn drives loss of genetic diversity. Many studies provide evidence of declines in genetic diversity; however, controversy exists within the literature, as some studies show evidence of no change in genetic diversity despite decades of overharvesting. The apparent discrepancy in the literature should therefore be examined to understand what biological and ecological processes are driving the differences in results. Here, we assess how different factors contribute to fisheries-induced susceptibility to declines in genetic diversity by first focusing on the different roles of genetic markers. Second, we assess how habitat type and conditions contribute to loss of genetic diversity. Third, we assess how life history and physiology affects catchability and loss of genetic diversity. Finally, we discuss how coinciding abiotic and biotic factors influence the intensity of genetic loss. We find a multitude of these factors could be interacting to influence how results are perceived and how intense the loss of genetic diversity can be. Future studies should carefully consider the methodology of genetic analysis used, as well as considerations of life history and ecology of the target species. Full article
(This article belongs to the Section Biology and Ecology)
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4 pages, 198 KiB  
Editorial
Assessment of Age and Growth in Fishes
by Ana Rita Vieira
Fishes 2023, 8(10), 479; https://doi.org/10.3390/fishes8100479 - 26 Sep 2023
Cited by 7 | Viewed by 3456
Abstract
Fish are the largest and most diverse group of vertebrates [...] Full article
(This article belongs to the Section Biology and Ecology)
13 pages, 8710 KiB  
Article
Successful Cryopreservation of Spermatogonia Stem Cells of Neotropical Catfish (Rhamdia quelen) and Enriched Germ Cell Transplantation into Common Carp (Cyprinus carpio) Testes
by Ivana F. Rosa, Emanuel R. M. Martinez, Melanie Digmayer, Lucas B. Doretto and Rafael H. Nóbrega
Fishes 2023, 8(10), 478; https://doi.org/10.3390/fishes8100478 - 25 Sep 2023
Cited by 8 | Viewed by 2388
Abstract
Cryopreservation and transplantation of spermatogonial stem cells (SSCs) offer new possibilities in the conservation of valuable genetic resources. Therefore, the present study developed a cryopreservation method for whole testicular tissue and for spermatogonial stem cells of jundia catfish (Rhamdia quelen) and [...] Read more.
Cryopreservation and transplantation of spermatogonial stem cells (SSCs) offer new possibilities in the conservation of valuable genetic resources. Therefore, the present study developed a cryopreservation method for whole testicular tissue and for spermatogonial stem cells of jundia catfish (Rhamdia quelen) and developed an enriched germ cell transplantation of jundia catfish into depleted common carp (Cyprinus carpio) testes. Our findings from whole testes indicate that the cryoprotectants MeOH (1.3 M), DMSO (1.4 M), and EG (1.4 M) resulted in high cell viability rates of 67%, 62%, and 51.5%, respectively. Notably, in the case of enriched post-thaw SSCs, DMSO exhibited the highest cell viability at 27%, followed by EG at 16% and MeOH at 7%. Additionally, we observed the successful colonization and proliferation of jundia germ cells within the recipient gonads of common carp following transplantation. Notably, Sertoli cells were identified in the recipient gonads, providing support to the stained donor germ cells and indicated the formation of cysts. Our data suggest that cryopreserving entire testicular tissue presents a viable alternative to cryopreserving isolated testicular cells, and the spermatogonial cells isolated from testes of jundia retained transplantability characteristics. Nonetheless, more investigations are required to reach the goal of functional gamete and to assess the effectiveness of transplantation using these cryopreserved tissues. Taken together, proper cryopreservation methodology and transplantation technology could aid the preservation practice of fish genetic resources. Full article
(This article belongs to the Special Issue Reproductive Biology and Breeding of Fish)
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32 pages, 5898 KiB  
Article
High Endemism in an Endangered Biodiversity Hotspot: Phylogeny, Taxonomy and Distribution Patterns of Catfishes of the Psammocambeva Alpha-Clade (Siluriformes: Trichomycteridae) from the Rio Doce Basin, Brazil
by Wilson J. E. M. Costa, José Leonardo O. Mattos, Maria Anaïs Barbosa, Paulo J. Vilardo and Axel M. Katz
Fishes 2023, 8(10), 474; https://doi.org/10.3390/fishes8100474 - 22 Sep 2023
Cited by 5 | Viewed by 2295
Abstract
The Rio Doce basin is situated in a biodiversity hotspot, with some fish groups still superficially known. The intense process of habitat loss and water contamination justifies efforts to speed up the pace of describing fish species diversity. Herein, we focus on a [...] Read more.
The Rio Doce basin is situated in a biodiversity hotspot, with some fish groups still superficially known. The intense process of habitat loss and water contamination justifies efforts to speed up the pace of describing fish species diversity. Herein, we focus on a clade of trichomycterine catfishes, subgenus Psammocambeva, genus Trichomycterus, performing a multigene phylogenetic analysis, which integrated to a comparative morphological analysis corroborates monophyly and relationships of four species complexes. Five new species are recognised and described. Species distribution patterns support the recognition of five areas of endemism for trichomycterines, most of which are well-known biodiversity centres: Serra do Espinhaço, Serra do Brigadeiro, Serra do Caparaó, Serra do Castelo, and upper-middle Rio Doce. Trichomycterine diversity in the Rio Doce basin, with 16 species, of which 15 belong to Psammocambeva, is lower than in the smaller neighbouring Rio Paraíba do Sul basin, with 21 species in five subgenera. Data suggest that species diversification in the former basin is relatively younger, following the initial diversification of Psammocambeva in the Miocene, whereas diversification in the latter basin has been estimated to have occurred during the Oligocene. This study reinforces the importance of naming new taxa and delimitating areas of endemism as primary tools for conservation strategies. Full article
(This article belongs to the Section Taxonomy, Evolution, and Biogeography)
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15 pages, 1114 KiB  
Article
The Effects of Dietary Fermented Soybean Meal Supplementation on the Growth, Antioxidation, Immunity, and mTOR Signaling Pathway of Juvenile Coho Salmon (Oncorhynchus kisutch)
by Qin Zhang, Qiuyue Yang, Mengjie Guo, Fanghui Li, Meilan Qin, Yi Xie, Jian Xu, Yongqiang Liu and Tong Tong
Fishes 2023, 8(9), 448; https://doi.org/10.3390/fishes8090448 - 5 Sep 2023
Cited by 10 | Viewed by 2236
Abstract
This experiment aims to investigate the effects of partial replacement of fish meal (FM) by soybean meal (SBM) and/or fermented soybean meal (FSBM) on the growth, serum biochemistry, digestion, antioxidation, immunity, and mTOR signaling pathway of juvenile coho salmon (Oncorhynchus kisutch). [...] Read more.
This experiment aims to investigate the effects of partial replacement of fish meal (FM) by soybean meal (SBM) and/or fermented soybean meal (FSBM) on the growth, serum biochemistry, digestion, antioxidation, immunity, and mTOR signaling pathway of juvenile coho salmon (Oncorhynchus kisutch). Four iso-nitrogen and iso-lipid diets were designed and fed to four groups of juvenile coho salmon (152.25 ± 2.96 g) in triplicate for 10 weeks. The four diets were the G0 diet (control group, containing 28% FM protein), the G1 diet (containing 10% SBM protein and 18% FM protein), the G2 diet (containing 5% SBM protein, 5% FSBM protein, and 18% FM protein), and the G3 diet (containing 10% FSBM protein and 18% FM protein). It was found that compared with the G0 diet (control group), the activities of catalase (CAT), superoxide dismutase (SOD), pepsin, trypsin, α-amylase, and lipase, and the expression levels of mammalian target of rapamycin (mtor), protein kinase B (akt), phosphatidylinositol 3-kinase (pi3k), plant ribosome S6K protein kinase (s6ks), and lysozyme (lyz) genes, of juvenile coho salmon fed the G3 diet increased significantly (p < 0.05), and the expression levels of tumor necrosis factor (tnf-α), interleukin-1β (il-1β), and interleukin-6 (il-6) genes of juvenile coho salmon fed the G3 diet decreased significantly (p < 0.05). However, there were no significant differences in growth, muscle composition, and serum biochemistry of juvenile coho salmon fed the G3 diet compared with the G0 diet (p > 0.05). In conclusion, replacing 10% FM protein with FSBM protein could improve the digestion, antioxidation, immunity, and mTOR signaling pathway of juvenile coho salmon. Full article
(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)
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15 pages, 4396 KiB  
Article
An Assessment of Microplastic Contamination in a Commercially Important Marine Fish, Harpadon nehereus (Hamilton, 1822)
by Kalpana Prusty, Vasantkumar Rabari, Krupal Patel, Daoud Ali, Saud Alarifi, Virendra Kumar Yadav, Dipak Kumar Sahoo, Ashish Patel and Jigneshkumar Trivedi
Fishes 2023, 8(9), 432; https://doi.org/10.3390/fishes8090432 - 23 Aug 2023
Cited by 26 | Viewed by 3376
Abstract
Microplastic (MP) pollution is a prevalent and global threat to fish. MP contamination was investigated in Harpadon nehereus collected from the principal fishing harbors of India’s northwest coast. A total of 213 specimens were collected from the major fishing harbors of Gujarat state (Jakhau, [...] Read more.
Microplastic (MP) pollution is a prevalent and global threat to fish. MP contamination was investigated in Harpadon nehereus collected from the principal fishing harbors of India’s northwest coast. A total of 213 specimens were collected from the major fishing harbors of Gujarat state (Jakhau, Okha, and Jaffrabad) and Maharashtra state (Mumbai). In the laboratory, the morphometric parameters of the specimens, such as total length and body weight, were measured. The collected specimens were analyzed for MP isolation using the previously documented protocol. MPs were quantified under a stereomicroscope, and physical parameters were recorded. All the examined specimens were found to be contaminated with MPs, with an abundance of 6.98 ± 6.73 MPs/g. The maximum contamination of MPs was recorded at the study site in Jaffrabad, followed by Jakhau, Mumbai, and Okha. Morphometric analysis of MPs revealed threads to be the most dominant shape. Black and blue MPs with a 1–2 mm size were the predominant recorded types. The chemical composition of extracted MPs revealed polyethylene (PE), polystyrene (PS), and polyurethane (PU) as polymer compositions. Conclusively, the findings highlighted a greater menace to seafood safety due to trophic transfer, which causes a hazardous effect on human health. Full article
(This article belongs to the Special Issue The Effect of Nano and Micro-Plastic on Fish)
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18 pages, 4207 KiB  
Article
Effects of Co-Fermented Feed Using Lactobacillus acidophilus, Limosilactobacillus reuteri and Lactiplantibacillus plantarum on Growth, Antioxidant Capacity, Fatty Acids and Gut Microbiota of Largemouth Bass (Micropterus salmoides)
by Zixin Yang, Peiqin Liu, Qing Kong, Yongyan Deng, Wenqi Zhang, Guohuan Xu and Huijuan Tang
Fishes 2023, 8(9), 433; https://doi.org/10.3390/fishes8090433 - 23 Aug 2023
Cited by 14 | Viewed by 3333
Abstract
The effects of diets fermented with compound probiotics, namely Lactobacillus acidophilus, Limosilactobacillus reuteri and Lactiplantibacillus plantarum, on the growth performance, physiological and biochemical indexes, fatty acid composition and intestinal health of juvenile largemouth bass (Micropterus salmoides) were investigated. Three [...] Read more.
The effects of diets fermented with compound probiotics, namely Lactobacillus acidophilus, Limosilactobacillus reuteri and Lactiplantibacillus plantarum, on the growth performance, physiological and biochemical indexes, fatty acid composition and intestinal health of juvenile largemouth bass (Micropterus salmoides) were investigated. Three hundred healthy juvenile M. salmoides (5.29 ± 0.02 g) were selected and randomly divided into two groups with triplicates for each. The basic diet was set as the control group (CON), and fermentation of the basic diet with a mixed bacterial solution (1.8 × 109 cfu/mL, L. acidophilus:L. reuteri:L. plantarum = 1:1:1) was set as the fermentation group (FER). Fish were hand fed to satiation for 56 days and two-thirds of the culture water was renewed every 3 days. The results showed that feed intake of fish in the FER group was significantly lowered, thereby increasing feed efficiency (FE) and protein efficiency (PER) (p < 0.05). Serum alanine aminotransferase (ALT) activity was significantly decreased, and catalase (CAT) activity was significantly increased in the FER group (p < 0.05). The liver superoxide dismutase activity (SOD) was significantly enhanced, and intestinal trypsin was significantly increased in the FER group (p < 0.05). Being fed with the fermentation diet significantly increased the content of n-3 polyunsaturated fatty acids (PUFA), docosahexaenoic acid (DHA) and the n-3/n-6 PUFAs ratios in the liver (p < 0.05). Intestinal histology showed that villus height and width of the intestine and the number of goblet cells were significantly increased in the FER group (p < 0.05). Those fed with fermentation diets had limited diversity of gut microbiota. Compared to the CON group, the relative abundance of Aeromonas decreased significantly (p < 0.05), while the relative abundance of Fusobacteria, Cetobacteria and Lactobacillusis in FER increased greatly in the gut microbiota of the FER group. In conclusion, fermented feed with the three probiotics effectively improved the feed utilization and antioxidant capacity, promoted digestion and absorption of dietary protein, improved the ability of synthesize DHA and n-3 PUFAs in the liver and reduced the abundance of pathogenic bacteria in the gut. Therefore, the present research provided a new way of co-fermented feed with three probiotics for the aquaculture of M. salmoides. Full article
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36 pages, 4292 KiB  
Review
Fish Welfare in Aquaculture: Physiological and Immunological Activities for Diets, Social and Spatial Stress on Mediterranean Aqua Cultured Species
by Mariano Dara, Pierluigi Carbonara, Claudia La Corte, Daniela Parrinello, Matteo Cammarata and Maria Giovanna Parisi
Fishes 2023, 8(8), 414; https://doi.org/10.3390/fishes8080414 - 12 Aug 2023
Cited by 27 | Viewed by 8978
Abstract
Welfare assessment currently is less well-characterized for aquatic animals and the classical methodologies used for terrestrial animals are not adequate to improve our knowledge about fish well-being. Among different approaches, the status of organism responses can be carried out using different physiological and [...] Read more.
Welfare assessment currently is less well-characterized for aquatic animals and the classical methodologies used for terrestrial animals are not adequate to improve our knowledge about fish well-being. Among different approaches, the status of organism responses can be carried out using different physiological and biochemical tools. Here, we present the state of the art regarding fish welfare, methodologies, and experimental results with a particular focus on two important Mediterranean aquaculture species, Sparus aurata and Dicentrarchus labrax. We introduce an approach using physiological stress-indicators, growth performance and swimming activity to investigate the effects of the implantation of electronic tags to facilitate the application of telemetry for aquaculture purposes. The application of telemetry to research on aquatic organisms has expanded recently, and its utilization needs to be better understood. The mentioned approaches have been discussed for application in different aquaculture methodologies. Moreover, social stress and territoriality are relevant factors in the evaluation of gregarious species that may have consequences on the conditions of animals farmed in captivity. These aspects, that may impair the ability of fish to respond to various stimuli or negatively influence the flesh quality, here are analysed through behavioural observation, flanked by the physiological and immunological approach. Full article
(This article belongs to the Special Issue Welfare and Sustainability in Aquaculture)
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25 pages, 2085 KiB  
Review
Bioaccumulation of Metals in Some Fish Species from the Romanian Danube River: A Review
by Anca Nicoleta Cordeli (Săvescu), Lucian Oprea, Mirela Crețu, Lorena Dediu, Marian Tiberiu Coadă and Diana-Nicoleta Mînzală
Fishes 2023, 8(8), 387; https://doi.org/10.3390/fishes8080387 - 26 Jul 2023
Cited by 12 | Viewed by 3661
Abstract
The Danube is the second-largest river in Europe and has been subject to pollution in the past. Additionally, in the last few years, the rapid pace of industrialization and urbanization has led to the inevitable pollution of this aquatic ecosystem by certain metals [...] Read more.
The Danube is the second-largest river in Europe and has been subject to pollution in the past. Additionally, in the last few years, the rapid pace of industrialization and urbanization has led to the inevitable pollution of this aquatic ecosystem by certain metals (essential and non-essential elements). This issue is considered the central problem of pollution in the Danube and is gaining increasing attention. Fish is a good source of proteins, polyunsaturated fatty acids (especially omega-3 fatty acids), essential vitamins, and minerals. Fish are often exposed to metals present in their aquatic environment through direct contact with contaminated water or by consuming organisms that have accumulated metals in their tissues; therefore, the elevated concentrations of metals in water and sediments are reflected in the fish flesh. In this context, the safety of fish and fishery products for human consumption is a public health concern. In the last two decades, more and more reports have shown that Danube River fish are contaminated with metals, causing great concern among consumers. The negative perception continues, although recent scientific studies show that metal levels in the edible parts of the fish are below acceptable limits. The objective of this study was to put together a multitude of scientific research studies that investigate the levels of some metals in various tissues of some fish species with high economic value in the Romanian market, as well as the levels of metals in the water and sediments. The collected data were then utilized to assess the potential health risks posed to humans. Full article
(This article belongs to the Special Issue Recent Advances in Aquaculture Production Technology)
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15 pages, 2168 KiB  
Article
Effects of Dietary Peppermint (Mentha piperita) Essential Oil on Growth Performance, Plasma Biochemistry, Digestive Enzyme Activity, and Oxidative Stress Responses in Juvenile Nile Tilapia (Oreochromis niloticus)
by Gustavo Augusto Carvalho Costacurta de Aguiar, Cristiana Leonor da Silva Carneiro, Daniel Abreu Vasconcelos Campelo, Rafael Costa Teixeira Rusth, João Felipe Ribeiro Maciel, Bernardo Baldisserotto, Jener Alexandre Sampaio Zuanon, Alexmiliano Vogel de Oliveira, Maria Goreti de Almeida Oliveira, Mariella Bontempo Duca de Freitas, Wilson Massamitu Furuya and Ana Lúcia Salaro
Fishes 2023, 8(7), 374; https://doi.org/10.3390/fishes8070374 - 20 Jul 2023
Cited by 12 | Viewed by 4250
Abstract
This study aimed to evaluate the supplementation of peppermint essential oil (Mentha piperita; PEO) in diets for juvenile Nile tilapia (Oreochromis niloticus). A feeding experiment with diets containing graded levels (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 g kg [...] Read more.
This study aimed to evaluate the supplementation of peppermint essential oil (Mentha piperita; PEO) in diets for juvenile Nile tilapia (Oreochromis niloticus). A feeding experiment with diets containing graded levels (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 g kg−1) of PEO was carried out with fish of 0.58 ± 0.08 g. The inclusion of graded levels of PEO in the diet improved the weight gain (0.52 g kg−1), feed intake (0.51 g kg−1), and feed conversion (0.51 g kg−1) of juvenile Nile tilapia in a quadratic pattern. Increasing levels of PEO also led to a linear decrease in body lipid content. The gut activity of the digestive enzymes amylase (0.54 g kg−1) and protease (0.39 g kg−1) increased quadratically, whereas lipase activity increased linearly. PEO increased the activity of the antioxidant enzymes catalase (CAT; 0.52 g kg−1) and superoxide dismutase (SOD; 0.58 g kg−1) while reducing the production of malonaldehyde (MDA; 0.40 g kg−1) and nitric oxide (NO; 0.63 g kg−1) in the liver. The results of this study provide evidence of the beneficial effects of PEO on the growth and health of Nile tilapia and recommend a dose of 0.6 g kg−1 as the optimal level of supplementation. Full article
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16 pages, 1783 KiB  
Review
Effect of Bacillus Probiotics on the Immunological Responses of Nile Tilapia (Oreochromis niloticus): A Review
by Vicent Michael Shija, Kwaku Amoah and Jia Cai
Fishes 2023, 8(7), 366; https://doi.org/10.3390/fishes8070366 - 13 Jul 2023
Cited by 34 | Viewed by 6739
Abstract
The use of antibiotics and therapeutics for Nile tilapia has increased along with its increased production and intensification. Probiotics have been studied as an alternative to the excessive use of antibiotics in fish diets. Studies have demonstrated that dietary Bacillus probiotic inclusion promotes [...] Read more.
The use of antibiotics and therapeutics for Nile tilapia has increased along with its increased production and intensification. Probiotics have been studied as an alternative to the excessive use of antibiotics in fish diets. Studies have demonstrated that dietary Bacillus probiotic inclusion promotes faster growth and disease resistance in farmed fish species. Despite advances in research, there is still uncertainty about the mechanisms controlling the immune response of fish. In this review, we summarize and discuss recent research on the immune responses of Nile tilapia to Bacillus probiotics. Through the use of immunological information including phagocytosis, lysozyme activity, respiratory activity, antioxidant proteins, complement activity, and immune-related gene expression, researchers hope to develop effective strategies for successfully using Bacillus probiotics in Oreochromis niloticus farming. Full article
(This article belongs to the Special Issue Potential Application of Probiotics for Sustainable Aquaculture)
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18 pages, 4469 KiB  
Article
Effect of the Potential Probiotic Vibrio proteolyticus DCF12.2 on the Immune System of Solea senegalensis and Protection against Photobacterium damselae subsp. piscicida and Vibrio harveyi
by Alberto Medina, Jorge García-Márquez, Miguel Ángel Moriñigo and Salvador Arijo
Fishes 2023, 8(7), 344; https://doi.org/10.3390/fishes8070344 - 30 Jun 2023
Cited by 8 | Viewed by 2236
Abstract
Some of the characteristics of probiotics used in aquaculture are the antagonistic activity against pathogens and the activation of the immune response. Moreover, some probiotics with common antigens to pathogens can produce antibodies that react with these pathogens. One of those potential probiotics [...] Read more.
Some of the characteristics of probiotics used in aquaculture are the antagonistic activity against pathogens and the activation of the immune response. Moreover, some probiotics with common antigens to pathogens can produce antibodies that react with these pathogens. One of those potential probiotics is Vibrio proteolyticus DCF12.2, a strain with the capacity to produce antibodies in soles (Solea senegalensis) that react with Photobacterium damselae subsp. piscicida and Vibrio harveyi antigens. Therefore, the objective of the work was to determine the capacity of DCF12.2 to activate the immune response in the sole, providing protection against both pathogens. For this purpose, DCF12.2 was administered to cultured soles by intraperitoneal injection, bath, and diet. The DCF12.2 strain activated the gene expression related to the fish immune response and increased the antibody production with cross-reaction to P. damselae subsp. piscicida and V. harveyi cells. Challenges with P. damselae subsp. piscicida resulted in a 30–40% relative percent survival (RPS) through DCF12.2 treatments. After challenge with V. harveyi, only intraperitoneal treatment protected the fish (67% RPS). In conclusion, the DCF12.2 strain showed great potential to be used to prevent diseases caused by both pathogens, and indicates a way to use probiotics as live vaccines. Full article
(This article belongs to the Special Issue Potential Application of Probiotics for Sustainable Aquaculture)
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15 pages, 912 KiB  
Article
A Comparison of the Physiological Responses to Heat Stress of Two Sizes of Juvenile Spotted Seabass (Lateolabrax maculatus)
by Huihui Qin, Zhongying Long, Zhangfan Huang, Jianrong Ma, Lumin Kong, Yi Lin, Hao Lin, Sishun Zhou and Zhongbao Li
Fishes 2023, 8(7), 340; https://doi.org/10.3390/fishes8070340 - 28 Jun 2023
Cited by 16 | Viewed by 2554
Abstract
Temperature affects the metabolism of fish, and fish of different sizes have different tolerances to temperature. The aim of this experiment was to compare two sizes of juvenile spotted seabass, Lateolabrax maculatus (with average weights of 57.91 ± 11.57 g and 13.92 ± [...] Read more.
Temperature affects the metabolism of fish, and fish of different sizes have different tolerances to temperature. The aim of this experiment was to compare two sizes of juvenile spotted seabass, Lateolabrax maculatus (with average weights of 57.91 ± 11.57 g and 13.92 ± 2.77 g, respectively) for changes in physiological, biochemical, and molecular mechanisms under acute heat stress. Experimental fish were exposed to acute temperature increasing from 23 °C to 32 °C, and the mortality rate was noted at various heat stress exposures (0, 3, 6, 12, 24, 48, and 72 h). Moreover, serum and liver were obtained before and after heat stress. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), superoxide dismutase (SOD), malondialdehyde (MDA), lactic acid (LD), lactate dehydrogenase (LDH), glucose, and hepatic glycogen, and the expression of heat shock proteins (HSP70, HSP90) and apoptosis-related genes (BAX, caspase-3) in two sizes of spotted seabass were measured. Results showed that the contents of AST, ALT, SOD, MDA, LD, and glucose as well as the expression level of BAX and mortality were higher in large spotted seabass than in small spotted seabass within 12 h. These results indicate that the large spotted seabass had higher levels of oxidative stress and more severe liver damage, resulting in a higher mortality. Furthermore, the HSPs expression level of small spotted seabass was higher and the mortality was lower than that of large spotted seabass. Therefore, we considered that the large spotted seabass has lower levels of HSPs expression, causing their physiological response to be elevated to resist heat stress. In conclusion, spotted seabass with larger size has a poorer tolerance to heat stress compared with spotted seabass with smaller size. The smaller fish size was possibly resistant to heat stress by regulating the HSPs expression level in a more active extent. Full article
(This article belongs to the Section Physiology and Biochemistry)
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20 pages, 395 KiB  
Review
Thermal Effects on Ecological Traits of Salmonids
by Bror Jonsson
Fishes 2023, 8(7), 337; https://doi.org/10.3390/fishes8070337 - 25 Jun 2023
Cited by 19 | Viewed by 4065
Abstract
Here, I review thermal influences on metabolic rates and aerobic scope; growth; adult body size; and reproductive and behavioural traits, such as tendency and timing of the migration of salmonid fishes. A thermal window bounded by the upper and lower incipient lethal temperatures [...] Read more.
Here, I review thermal influences on metabolic rates and aerobic scope; growth; adult body size; and reproductive and behavioural traits, such as tendency and timing of the migration of salmonid fishes. A thermal window bounded by the upper and lower incipient lethal temperatures (UILT and LILT) determines where salmonids can survive. For most salmonids, LILT is close to 0 and UILT is between 20 and 30 °C. UILT and LILT are influenced by the acclimation temperature. Thermal tolerance is affected by fish size and ambient oxygen content, which decreases with increasing temperature. Standard metabolic rate (SMR), the energy required to maintain essential functions, increases with temperature, whereas maximum metabolic rate (MMR) increases with temperature until reaching a peak (pejus). Then, it decreases gradually to zero, i.e., the upper critical limit (TCrit). Aerobic scope (AS = MMR-SMR) reaches its maximum at the pejus temperature. Metabolic rates and aerobic scope can be modified by temperatures that the fish experiences during embryogenesis and possibly also as larvae and young fry. At maximum feeding, maximum growth increases to a point at or below the pejus temperature. The optimum temperature for growth decreases with reduced food intake and increased body size. As for metabolic rate, the growth rate is influenced by the temperature during embryonic development. In a warmer climate, adult body size is expected to decrease chiefly because of a younger age at maturity. Parental fish retained at a higher temperature during maturation produce larger eggs, and this change in egg size may also be transferred to next-generation offspring. Furthermore, embryogenesis in warmer water leads to larger gonad and egg sizes at maturity. Water temperature influences locomotion, foraging and migratory activity. In a warmer climate, juveniles migrate to the sea earlier in spring. In addition, higher embryo temperature leads to delayed return of adult salmon from the ocean. Thus, temperature affects life history traits of salmonid fishes, partly as a direct effect on metabolic rates and food consumption and partly induced as a phenotypically plastic effect. The phenotypically plastic response may preadapt offspring to perform better in the expected future thermal environment. Full article
(This article belongs to the Special Issue Effect of Climate Change on Salmonid Fishes in Rivers)
19 pages, 1957 KiB  
Article
Herbivorous Grass Carp (Ctenopharyngodon idella) Exhibit Greater Olfactory Response to Amino Acids Than Filter-Feeding Bighead (Hypophthalmichthys nobilis) and Silver Carp (Hypophthalmichthys molitrix)
by Mark L. Wildhaber, Benjamin M. West, Karlie K. Ditter, Alex S. Peterson, Robin D. Calfee and Zachary D. Beaman
Fishes 2023, 8(7), 334; https://doi.org/10.3390/fishes8070334 - 23 Jun 2023
Cited by 3 | Viewed by 2564
Abstract
Due to their invasiveness in North America, grass (Ctenopharyngodon idella), bighead (Hypophthalmichthys nobilis), and silver carp (Hypophthalmichthys molitrix) are management priorities. Comparing electrophysiological responses to olfactory cues, such as amino acids, could help identify stimuli to facilitate management [...] Read more.
Due to their invasiveness in North America, grass (Ctenopharyngodon idella), bighead (Hypophthalmichthys nobilis), and silver carp (Hypophthalmichthys molitrix) are management priorities. Comparing electrophysiological responses to olfactory cues, such as amino acids, could help identify stimuli to facilitate management efforts (i.e., repellants or baits). We assessed olfactory response magnitude to individual amino acids between fish species using electro-olfactogram recording techniques (EOG). We measured EOG responses (peak EOG magnitude) of juvenile grass (n = 21), bighead (n = 21), and silver carp (n = 22) to 10−4 molar amino acid solutions containing one of L-alanine, L-arginine, L-aspartic acid, L-asparagine, L-glutamine, or L-glutamic acid. Amino acid EOG responses differed across species; grass carp had the greatest mean EOG response. Statistical analyses showed no inter- or intra-specific differences in EOG response among amino acids. The greater EOG response of grass carp matched their selective grazing habits compared to more passive, generalist-tending, filter-feeding bighead and silver carp. All amino acids elicited significant EOG responses in all species, meaning they are candidates for future behavioral research. Such research could explore the management potential of amino acids, testing if amino acids are attractants or deterrents that could facilitate the removal of these fishes by congregating and/or directing movement. Full article
(This article belongs to the Special Issue Advances in Ecology and Management of Aquatic Invasive Species)
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16 pages, 2840 KiB  
Article
Nano-Curcumin/Chitosan Modulates Growth, Biochemical, Immune, and Antioxidative Profiles, and the Expression of Related Genes in Nile tilapia, Oreochromis niloticus
by Hiam Elabd, Heba H. Mahboub, Shimaa M. R. Salem, Abdelwahab M. Abdelwahab, Khairiah Mubarak Alwutayd, Mohamed Shaalan, Sameh H. Ismail, Abdelfattah M. Abdelfattah, A. Khalid, Abdallah Tageldein Mansour, Heba S. Hamed and Hadeer Youssuf
Fishes 2023, 8(7), 333; https://doi.org/10.3390/fishes8070333 - 21 Jun 2023
Cited by 30 | Viewed by 2947
Abstract
This study aimed to evaluate the effects of dietary supplementation with nano-curcumin (NCur) and a nano-curcumin/chitosan blend (NCur/Ch) on growth performance, digestibility, immune response, antioxidant status, intestinal morphometric characters, and gene regulation in Nile tilapia. Fish (n = 180, initial body weight [...] Read more.
This study aimed to evaluate the effects of dietary supplementation with nano-curcumin (NCur) and a nano-curcumin/chitosan blend (NCur/Ch) on growth performance, digestibility, immune response, antioxidant status, intestinal morphometric characters, and gene regulation in Nile tilapia. Fish (n = 180, initial body weight = 12.0 ± 0.53 g) received supplementary NCur at rates of 0 (control), 0.00625, and 0.0125, and NCur/Ch at rates of 0.00625 + 0.5 g/kg diet for 4 weeks. Growth performance parameters (final weight and length, body mass gain, specific growth, and length gain rates) were markedly increased, and the feed conversion ratio was significantly decreased in the NCur- and NCur/Ch-supplemented groups. Digestive enzyme (amylase), immune response markers (immunoglobulin M, nitrous oxide, and lysozyme activity), plasma albumin, and total protein were increased significantly, mainly with a diet supplemented with 0.00625 g NCur/kg. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose, and cortisol levels decreased in the supplemented groups compared to the control. Significantly increased glutathione peroxidase (GPx) and decreased malondialdehyde (MDA) levels were observed in the NCur/Ch group. Superoxide dismutase (SOD) activity was improved in the 0.0125 NCur group. Intestinal morphometric characters, including villus length, width, interspace, and goblet cell abundance, were increased to cope with improved growth performance and were associated with upregulation of insulin-like growth factor 1 (igf-1) and complement C-5 (cc5) compared to the control group. Therefore, NCur and an NCur/Ch blend could be supplemented in the Nile tilapia diets as a natural alternative to promote growth, digestion, immune status, liver function, antioxidant status, and related gene expression in O. niloticus. Full article
(This article belongs to the Section Sustainable Aquaculture)
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18 pages, 2067 KiB  
Review
A Selected Review of Impacts of Ocean Deoxygenation on Fish and Fisheries
by Hongsik Kim, Ana C. Franco and U. Rashid Sumaila
Fishes 2023, 8(6), 316; https://doi.org/10.3390/fishes8060316 - 14 Jun 2023
Cited by 17 | Viewed by 7390
Abstract
Oxygen is crucial for the survival of marine species. Yet, the ocean has experienced a loss of approximately 2% of its oxygen inventory since the last century, resulting in adverse impacts on marine life and ecosystems. In particular, changes in the gap between [...] Read more.
Oxygen is crucial for the survival of marine species. Yet, the ocean has experienced a loss of approximately 2% of its oxygen inventory since the last century, resulting in adverse impacts on marine life and ecosystems. In particular, changes in the gap between the supply and demand for dissolved oxygen lead to physiological and ecological variations, which cause alterations in habitats and food webs for fish and ecosystem services. These changes vary over time and by region, and the heterogeneous characteristics of marine species bring about non-linear consequences to human society. Despite this, identifying the potential ripple effects of deoxygenation on human society is challenging due to the integrated impacts of other stressors, such as global warming and ocean acidification, and their varying changes depending on environmental conditions and regions, such as upwelling and eutrophication. Therefore, we conducted a literature review on ocean deoxygenation and its effects on fish dynamics and the ecosystem, with a focus on the environmental and societal impact, to present crucial considerations and pathways for future research on ocean deoxygenation. We found that quantitative approaches are necessary to assess the dynamic changes under deoxygenation, and the consequent effects on marine ecosystems should be verified to exploit the natural resources from the ocean. One of the most reliable approaches to quantifying the ripple impacts of deoxygenation is to model spatial and temporal changes with other climate stressors, forming a global network encompassing socio-economic and regional effects of this global change to facilitate and improve capabilities to address the impacts of ocean deoxygenation. Full article
(This article belongs to the Special Issue Fisheries Policies and Management)
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15 pages, 2558 KiB  
Article
Lionfish Diet Composition at Three Study Sites in the Aegean Sea: An Invasive Generalist?
by Ioannis E. Batjakas, Athanasios Evangelopoulos, Maria Giannou, Sofia Pappou, Eleftheria Papanikola, Maria Atsikvasi, Dimitris Poursanidis and Chrysoula Gubili
Fishes 2023, 8(6), 314; https://doi.org/10.3390/fishes8060314 - 13 Jun 2023
Cited by 7 | Viewed by 2848
Abstract
The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in [...] Read more.
The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in terms of numerical abundance and frequency of occurrence was used to compare lionfish’s diet between these sites. Lionfish largely preyed upon teleosts (4% to 83% numerical abundance and 16% to 58% frequency of occurrence, depending on the site) and decapods (12% to 95% numerical abundance and 11% to 81% frequency of occurrence). The most important teleost families in lionfish’s diet were Gobiidae, Labridae, and Scorpaenidae, while decapods and especially the family Scyllaridae and the genus Plesionika were the dominant decapod prey items. The lionfish was found to be an especially successful generalist across the study sites, an opportunistic, predatory species overall, and at the same time, at a local level, it seems to be an equally successful specialist that could increase the predation mortality of already stressed prey populations and can be a serious threat to endemic, critically endangered, and/or commercially important species. Full article
(This article belongs to the Special Issue Advances in Ecology and Management of Aquatic Invasive Species)
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25 pages, 1301 KiB  
Review
Non-Linear Analyses of Fish Behaviours in Response to Aquatic Environmental Pollutants—A Review
by Harkaitz Eguiraun and Iciar Martinez
Fishes 2023, 8(6), 311; https://doi.org/10.3390/fishes8060311 - 12 Jun 2023
Cited by 2 | Viewed by 2353
Abstract
Analysis of fish behaviour is an effective way to indirectly identify the presence of environmental pollutants that negatively affect fish life, its production and quality. Monitoring individual and collective behaviours produces large amounts of non-linear data that require tailor-suited computational methods to interpret [...] Read more.
Analysis of fish behaviour is an effective way to indirectly identify the presence of environmental pollutants that negatively affect fish life, its production and quality. Monitoring individual and collective behaviours produces large amounts of non-linear data that require tailor-suited computational methods to interpret and manage the information. Fractal dimension (FD) and entropy are two groups of such non-linear analysing methods that serve as indicators of the complexity (FD) and predictability (entropy) of the behaviours. Since behavioural complexity and predictability may be modulated by contaminants, the changes in its FD and entropy values have a clear potential to be embedded in a biological early warning system (BEWS), which may be particularly useful in Precision Fish Farming settings and to monitor wild populations. This work presents a review of the effects of a wide range of environmental contaminants, including toxic compounds, cleaning and disinfecting agents, stimulant (caffeine), anaesthetics and antibiotics, heavy metals (lead, cupper, and mercury), selenium, pesticides and persistent environmental pollutants, on the FD and entropy values of collective and individual behavioural responses of different fish species. All the revised studies demonstrate the usefulness of both FD and entropy to indicate the presence of pollutants and underline the need to consider early changes in the trend of the evolution of their values prior to them becoming significantly different from the control values, i.e., while it is still possible to identify the contaminant and preserve the health and integrity of the fish. Full article
(This article belongs to the Special Issue Trace Elements, Drugs, Small Compounds and Antioxidants in Fish)
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13 pages, 2979 KiB  
Article
Seasonal Dynamics and Environmental Drivers of Goliath Grouper (Epinephelus itajara) Sound Production
by Lauran R. Brewster, Ali K. Ibrahim, James Locascio, Breanna C. DeGroot, Laurent M. Chérubin and Matthew J. Ajemian
Fishes 2023, 8(6), 293; https://doi.org/10.3390/fishes8060293 - 1 Jun 2023
Viewed by 2351
Abstract
The Goliath groupers are known to produce characteristic low frequency vocalizations (“calls”) during spawning aggregations and as part of territorial behavior. Acoustic monitoring for Goliath grouper calls around Florida has historically occurred between July and December to capture the spawning season, with a [...] Read more.
The Goliath groupers are known to produce characteristic low frequency vocalizations (“calls”) during spawning aggregations and as part of territorial behavior. Acoustic monitoring for Goliath grouper calls around Florida has historically occurred between July and December to capture the spawning season, with a particular focus on August–November. Because of the unique waveform of the Goliath grouper call, we implemented a noise adaptive matched filter to automatically detect Goliath grouper calls from year-round passive acoustic recordings at two wrecks off Florida’s Gulf of Mexico coast. We investigated diel, temporal and environmental factors that could influence call rates throughout the year. Call rates peaked in August, around 0300 EST and just after the full moon. The Goliath groupers were more vocal when background noise was between 70 and 110 dB re 1 µPa. An additional smaller peak in call rates was identified in May, outside of the typical recording period, suggesting there may be other stimuli besides spawning that are eliciting high sound production in this species. Goliath grouper sound production was present year-round, indicative of consistent communication between individuals outside the spawning season. Full article
(This article belongs to the Special Issue Advances in Atlantic Goliath Grouper Research)
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16 pages, 1620 KiB  
Article
Biomass Quantification of the Critically Endangered European eel from Running Waters Using Environmental DNA
by Sara Fernandez, Álvaro Gutiérrez, Dumas Deconinck, Jose Luis Martinez, Almudena Alvarez, Isabel Marquez, Gonzalo Machado-Schiaffino and Eva Garcia-Vazquez
Fishes 2023, 8(6), 279; https://doi.org/10.3390/fishes8060279 - 24 May 2023
Cited by 4 | Viewed by 2900
Abstract
The European eel Anguilla anguilla is a critically endangered catadromous species. There is an urgent need for close surveillance of the populations that are still viable in European rivers. The species is difficult to observe in freshwater because of its bottom-dwelling behavior; the [...] Read more.
The European eel Anguilla anguilla is a critically endangered catadromous species. There is an urgent need for close surveillance of the populations that are still viable in European rivers. The species is difficult to observe in freshwater because of its bottom-dwelling behavior; the currently employed methods of eel monitoring in Europe based on the physical capture of individuals are stressful and may cause mortality. Here, we present a new highly sensitive method based on an A. anguilla-specific qPCR marker designed within the cytochrome oxidase I mitochondrial gene for application on environmental DNA (eDNA). Since the detectability of eDNA depends on the hydrographic conditions, we applied correction for altitude and a linear model and were able to predict the eel biomass from the eDNA in the different rivers of northern Spain still holding wild populations. The method was validated by electrofishing surveys. This novel eDNA-based marker allows for estimating the European eel biomass in running waters from small 1.5 L water samples and could complement, or replace in some cases, current eel surveys without disturbing wild populations. Full article
(This article belongs to the Special Issue Biology and Ecology of Eels)
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17 pages, 1833 KiB  
Article
Environmental and Genetic (vgll3) Effects on the Prevalence of Male Maturation Phenotypes in Domesticated Atlantic Salmon
by Thomas W. K. Fraser, Tom J. Hansen and Per Gunnar Fjelldal
Fishes 2023, 8(5), 275; https://doi.org/10.3390/fishes8050275 - 22 May 2023
Cited by 7 | Viewed by 2024
Abstract
Pre-harvest male maturation is problematic for Atlantic salmon (Salmo salar) farmers and is regulated by the environment and genetics (e.g., vgll3). Five families of all-male salmon parr (produced using YY males crossed with XX females) with different vgll3 genotypes were [...] Read more.
Pre-harvest male maturation is problematic for Atlantic salmon (Salmo salar) farmers and is regulated by the environment and genetics (e.g., vgll3). Five families of all-male salmon parr (produced using YY males crossed with XX females) with different vgll3 genotypes were split between three environmental regimes in January 2018. The “advanced maturation” regime used elevated temperature (16 °C) and continuous light from January 2018 with post-smolt maturation assessed in March 2018. The “extended freshwater” regime used ambient freshwater (1–16 °C) and simulated natural photoperiod (SNP) with post-smolt maturation assessed in November 2018. The “sea transfer” regime used ambient temperatures (1–14 °C) and SNP in freshwater until May 2018 when they were transferred to 9 °C seawater with natural photoperiod for 2.5 years (final mean weight of circa. 14 kg) and assessed for post-smolt maturation, 1 sea-winter (1 SW) maturation, and 2 sea-winter (2 SW) maturation in the autumn (November/December) of 2018, 2019, and 2020, respectively. Post-smolt maturation was highest in the advanced maturation and extended freshwater regimes (39–99% depending on family) and lowest in the sea transfer regime (0–95% depending on family). In the sea transfer regime, maturity incidence increased over time (0–95% post-smolt maturation, 1–100% 1 SW, and 50–90% 2 SW maturation, depending on family). In all regimes, those homozygous for the pre-designated vgll3 “early” maturing allele had the highest incidences of maturation whilst those homozygous for the “late” allele had the lowest. A low percentage of 2 SW phenotypic and genetic females were found (0–5% depending on family), one of which was successfully crossed with an XY male resulting in progeny with an approx. 50/50 sex ratio. These results show (i) post-smolt maturation varies dramatically depending on environment although genetic regulation by vgll3 was as expected, and (ii) crossing YY sperm with XX eggs can result in XX progeny which can themselves produce viable progeny with an equal sex ratio when crossed with an XY male. Full article
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23 pages, 8715 KiB  
Article
Dorsal Fin Spines and Rays for Nonlethal Ageing of Goliath Grouper Epinephelus itajara
by Jessica L. Carroll, Robert D. Ellis, Angela B. Collins and Debra J. Murie
Fishes 2023, 8(5), 239; https://doi.org/10.3390/fishes8050239 - 3 May 2023
Cited by 4 | Viewed by 2703
Abstract
Atlantic Goliath Grouper, Epinephelus itajara, the largest grouper in the western North Atlantic, exhibits life history characteristics (e.g., it is slow-growing, long-lived, and late-maturing) that make it particularly susceptible to fishing pressure. Otoliths, the structure typically processed for age determination, are usually [...] Read more.
Atlantic Goliath Grouper, Epinephelus itajara, the largest grouper in the western North Atlantic, exhibits life history characteristics (e.g., it is slow-growing, long-lived, and late-maturing) that make it particularly susceptible to fishing pressure. Otoliths, the structure typically processed for age determination, are usually collected as part of fishery monitoring, but otoliths are not available from Goliath Grouper due to a harvest moratorium enacted in 1990 for United States waters. Alternative structures—such as dorsal fin rays or spines—can be acquired for ageing via nonlethal sampling and may provide reliable age estimates. Since 2006, the Florida Fish and Wildlife Conservation Commission (FWC) has been collecting incidental Goliath Grouper samples from mortality events including those from cold kills and red tides. Corresponding otolith, dorsal fin ray and dorsal fin spine samples were compared to determine the accuracy and precision of the external ageing structures. Marginal increment analyses indicated that annulus (translucent zone) deposition occurred primarily in March–June on spines and in April–June on rays. While ages determined from both rays and spines exhibited high precision, the accuracy compared to otolith ages was low as a result of systematic underageing of both external structures, particularly at the oldest age classes. A correction factor was applied to rays and spines that remedied the underageing, but the correction factor was more successful for spines. An analysis of ray and spine section accuracy based on nonlethal structure removal from the fish (i.e., comparing ages from sections at the base of the structure within the body to those sectioned from the external surface of the body) determined that spines can be accurately aged when sampled distal of the base of the structure, but that rays cannot. Nonlethal sampling and ageing of Goliath Grouper spines facilitated by public participation could address management goals and help determine the offshore population age structure. Simultaneously, it could contribute critical data needed for a traditional stock assessment, should such a path be warranted by the recovery or management of the species. Full article
(This article belongs to the Special Issue Advances in Atlantic Goliath Grouper Research)
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15 pages, 4131 KiB  
Article
Investigating the Relationship between Aquaculture Investments, Training, and Environmental Factors in Guangdong: An Alternative Perspective
by Peiwen Wang, Isabel Mendes and Ramona Franić
Fishes 2023, 8(5), 237; https://doi.org/10.3390/fishes8050237 - 1 May 2023
Cited by 1 | Viewed by 2241
Abstract
This study investigates the interplay between investment, training, and environmental factors in the aquaculture industry in the Guangdong region of China. Using NIPALS regression to address multicollinearity, we identify the factors that significantly impact losses of aquaculture products due to environmental factors. Our [...] Read more.
This study investigates the interplay between investment, training, and environmental factors in the aquaculture industry in the Guangdong region of China. Using NIPALS regression to address multicollinearity, we identify the factors that significantly impact losses of aquaculture products due to environmental factors. Our findings highlight the importance of targeted training and education for fisherfolks and extension staff to enhance environmental management practices and reduce losses. We also emphasize the need to consider regional variability and challenges in developing universal models. Based on our results, we propose using innovative technology, fostering public–private partnerships, and adapting to regional variability to address environmental challenges. Finally, we suggest establishing a comprehensive monitoring and evaluation system to assess the effectiveness of interventions and promote evidence-based decision-making for sustainable development in the region’s aquaculture sector. Full article
(This article belongs to the Special Issue Fisheries and Blue Economy)
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16 pages, 1565 KiB  
Article
Reproduction of Hatchery-Reared Pike-Perch (Sander lucioperca) Fed Diet with Low-Marine-Ingredients: Role of Dietary Fatty Acids
by Géza Péter, Jovanka Lukić, Sylvain Milla, Zsuzsanna J. Sándor, Zsuzsanna Brlás-Molnár, László Ardó, Emese Bekefi and Uroš Ljubobratović
Fishes 2023, 8(5), 219; https://doi.org/10.3390/fishes8050219 - 22 Apr 2023
Cited by 4 | Viewed by 3137
Abstract
This research aimed to evaluate the reproductive potential of hatchery-reared (F1) pike-perch (Sander lucioperca) broodstock fed a commercial diet with low levels of long-chain polyunsaturated fatty acids (Lc-PUFA) and wild (F0) pike-perch broodstock fed forage fish. Reproductive parameters, including pseudogonadosomatic index [...] Read more.
This research aimed to evaluate the reproductive potential of hatchery-reared (F1) pike-perch (Sander lucioperca) broodstock fed a commercial diet with low levels of long-chain polyunsaturated fatty acids (Lc-PUFA) and wild (F0) pike-perch broodstock fed forage fish. Reproductive parameters, including pseudogonadosomatic index (PGSI), egg size, latency time, hatching rate, embryo survival, and eggs’ fatty acid (FA) composition, as well as plasma sex hormone, glucose and immunoglobulin levels after hormone injection, were analyzed. The results showed low PGSI (10% in F1 vs. 14% in F0) and embryo survival (24% in F1 vs. 61% in F0) in F1 broodstock, but a satisfactory hatching rate (63% in F1 vs. 78% in F0) and larval size (4.6 mm in F1 vs. 4.7 mm in F0). A low arachidonic acid (ARA) percentage in F1 fish eggs (1.32%), along with increased immunoglobulin levels (17.31 g/L), suggests that immune system activation might have depleted the reserves of ARA in F1 fish, which is the key fatty acid for successful oocyte maturation. We assumed that the administration of more sustainable diets, based on terrestrial plant ingredients, is not inferior to higher-quality diets based on marine ingredients. Full article
(This article belongs to the Section Nutrition and Feeding)
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17 pages, 3544 KiB  
Article
Effect of Photoperiod and Transfer Time on Atlantic Salmon Smolt Quality and Growth in Freshwater and Seawater Aquaculture Systems
by Enrique Pino Martinez, Albert Kjartan Dagbjartarson Imsland, Anne-Camilla Diesen Hosfeld and Sigurd Olav Handeland
Fishes 2023, 8(4), 212; https://doi.org/10.3390/fishes8040212 - 18 Apr 2023
Cited by 6 | Viewed by 4462
Abstract
Smoltification is a key process in Atlantic salmon aquaculture, given it prepares the fish for a successful transit from fresh to seawater. However, industry players have not yet reached a consensus on the best protocols to produce high-quality smolts. In this study, we [...] Read more.
Smoltification is a key process in Atlantic salmon aquaculture, given it prepares the fish for a successful transit from fresh to seawater. However, industry players have not yet reached a consensus on the best protocols to produce high-quality smolts. In this study, we assessed how the combination of two photoperiod regimes in freshwater (continuous light or LL, and natural photoperiod or LDN) and four transfer times to seawater (February, March, April, and May) affected smolt development and their subsequent growth in seawater until slaughter during commercial production. The results demonstrated that smoltification and growth in freshwater were only slightly modulated by the photoperiod treatment and were instead much more affected by the limiting effect of the low water temperature during that period. In seawater, the growth rate was the highest in the same groups, which had, however, experienced a delay in growth when in freshwater, and consequently, no differences in the final body weight between the eight treatments were found. Such compensatory growth in the sea was probably enhanced by the increasing smolt quality, which could allow for better performance in seawater. A significant link between the weight at slaughter and weight at transfer was observed only in the groups with a lower smolt quality (LL-Feb, LDN-Feb and LDN-Mar), which suggests that larger individuals could cope better with a saline environment. In contrast, smaller smolts probably suffered greater osmotic stress that hindered their performance at sea. Afterwards, as smolt quality increased in the subsequent transfer groups, the relevance of this size effect decreased. This means that the industry may benefit from transferring larger smolts to seawater, especially if these are suspected of having developed suboptimal seawater tolerance. Those individuals are likely to cope better with saline conditions than smaller smolts. Future research should focus on the possible long-term effects of freshwater-rearing regimes on smolt performance in the seawater phase. Full article
(This article belongs to the Section Sustainable Aquaculture)
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39 pages, 10964 KiB  
Article
Molecular Phylogeny, Taxonomy and Distribution Patterns of Trichomycterine Catfishes in the Middle Rio Grande Drainage, South-Eastern Brazil (Siluriformes: Trichomycteridae)
by Wilson J. E. M. Costa, Valter M. Azevedo-Santos, José Leonardo O. Mattos and Axel M. Katz
Fishes 2023, 8(4), 206; https://doi.org/10.3390/fishes8040206 - 15 Apr 2023
Cited by 6 | Viewed by 2984
Abstract
The Rio Grande drainage plays a key role in supplying water and electricity to large urban centres, but some components of its rich ichthyofauna are still poorly known. Based on our field inventories in the middle section of the drainage, we recognised 10 [...] Read more.
The Rio Grande drainage plays a key role in supplying water and electricity to large urban centres, but some components of its rich ichthyofauna are still poorly known. Based on our field inventories in the middle section of the drainage, we recognised 10 trichomycterine endemic species, of which 6 species are new and described herein. A molecular analysis (2600 bp for 43 taxa) indicated that the species of both subgenera do not form monophyletic groups. One species of the subgenus Cryptocambeva is closely related to species from the inner Brazilian Plateau, whereas other species of this subgenus are closely related to species endemic to smaller coastal basins. The species of the subgenus Paracambeva belong to different lineages of a clade endemic to the Rio Grande drainage. These species are diagnosed by the characters of their external morphology and osteology. A key to species identification is provided. The species distribution patterns support delimitation of three areas of endemism, which may have a relevant role for proposals of conservation strategies: the Uberaba, the São João-Sapucaí, and the Tamborete areas. The last one, a small area confined between the Serra da Canastra and the Rio Grande at the Furnas dam, is particularly important for sheltering three endemic trichomycterines and two loricariid catfishes. Full article
(This article belongs to the Special Issue Featured Papers in Taxonomy, Evolution, and Biogeography Section)
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12 pages, 2324 KiB  
Article
Phenotypic Stock Evaluation of Plagioscion magdalenae (Steindachner, 1878): A Species in the Dique Channel in Colombia
by Jordan Hernandez, Margarita Correa, Raquel Hernández-P, Adriana Bermúdez, Adriana Quintana-Canabal, David Laroze and Hugo A. Benítez
Fishes 2023, 8(4), 173; https://doi.org/10.3390/fishes8040173 - 24 Mar 2023
Cited by 2 | Viewed by 2132
Abstract
Inland fishing is an essential activity for the livelihood and food security the Colombian population. The knowledge and evaluation of exploited fish stocks is a priority to develop sustainable management and conservation strategies of the fisheries. To optimize the management processes of fishery [...] Read more.
Inland fishing is an essential activity for the livelihood and food security the Colombian population. The knowledge and evaluation of exploited fish stocks is a priority to develop sustainable management and conservation strategies of the fisheries. To optimize the management processes of fishery resources and conservation of species, it is necessary to evaluate the population structure and identification of stocks. Geometric morphometrics analysis have shown useful in the evaluation of fish stocks. This study focuses on the species Plagioscion magdalenae, commonly called “Pacora”, corvinata, or river croaker, which belongs to the family Sciaenidae, a family characterized as an important fishery resource. With the aim of generating a baseline about the state of the P. magdalenae population structure, samples were collected along the marshy complex of the Dique channel, Colombia, between December 2020 and October 2021. In this study, the existence of morphometric variability between individuals of Plagioscion magdalenae was found across sampling sites, Ciénaga de Capote and Ciénaga del Jobo; shape differences between location suggest the action of environmental pressures and the existence of anthropogenic pressures, such as unsustainable artisanal fishing. Full article
(This article belongs to the Special Issue Morphometrics in Fisheries and Aquaculture)
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27 pages, 3267 KiB  
Article
Assessing the Effects of Physical Barriers and Hypoxia on Red Drum Movement Patterns to Develop More Effective Management Strategies
by Steven M. Baker, Eric A. Reyier, Bonnie J. Ahr and Geoffrey S. Cook
Fishes 2023, 8(4), 171; https://doi.org/10.3390/fishes8040171 - 23 Mar 2023
Cited by 3 | Viewed by 2568
Abstract
Human modification of coastal ecosystems often creates barriers to fish movement. Passive acoustic telemetry was used to quantify movement patterns and habitat use of red drums (Sciaenops ocellatus) within and around a complex of coastal impoundments, and explored how the presence [...] Read more.
Human modification of coastal ecosystems often creates barriers to fish movement. Passive acoustic telemetry was used to quantify movement patterns and habitat use of red drums (Sciaenops ocellatus) within and around a complex of coastal impoundments, and explored how the presence of artificial structures (i.e., bollards and culverts) and a hypoxia-related mortality event impacted fish movement. Results indicated bollards impede the movement of individuals with head widths greater than the mean distance between bollards (~16.0 cm). Red drum home range area and daily distance traveled were related to water dissolved oxygen concentrations; as oxygen levels decreased, fish habitat use area decreased initially. However, continued exposure to hypoxic conditions increased fish cumulative daily distance traveled. When exposed to anoxic waters, fish daily distance traveled and rate of movement were greatly reduced. These findings suggest prolonged exposure to low dissolved oxygen in combination with artificial structures can reduce movement of red drum, increase risk of mortality, and decrease habitat connectivity. Constructing and maintaining (sediment and biofouling removal) larger culvert openings and/or using wider bollard spacing would improve water circulation in impoundments, increase habitat connectivity, and facilitate movement of large sportfish inhabiting Florida’s coastal waters. Full article
(This article belongs to the Special Issue Stock Assessment and Management for Sustainable Fisheries)
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12 pages, 501 KiB  
Communication
Determination of Multi-Class Antibiotics Residues in Farmed Fish and Shrimp from Sri Lanka by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS)
by G. D. T. M. Jayasinghe, Joanna Szpunar, Ryszard Lobinski and E. M. R. K. B. Edirisinghe
Fishes 2023, 8(3), 154; https://doi.org/10.3390/fishes8030154 - 4 Mar 2023
Cited by 8 | Viewed by 3991
Abstract
Antibiotics have been used to control the aquatic environment in both therapeutic and prophylactic ways. Antibiotics are particularly difficult to extract due to their strong interactions with biological matrices. In this study, UPLC-MS/MS method was developed and validated for quantitative confirmatory analysis of [...] Read more.
Antibiotics have been used to control the aquatic environment in both therapeutic and prophylactic ways. Antibiotics are particularly difficult to extract due to their strong interactions with biological matrices. In this study, UPLC-MS/MS method was developed and validated for quantitative confirmatory analysis of multi-class antibiotics residues in fish and shrimp. Fourteen antibiotics belonging to sulphonamides, β-lactams, quinolones, sulfones and macrolides were determined within one chromatographic run. The samples were suspended in 0.1 M HCl, and the analytes were extracted into ethyl acetate. The extracts were defatted with cyclohexane. The limits of quantification (LOQ) ranged from 0.24 to 1.32 µg kg−1 for fish and 0.42–1.62 µg kg−1 for shrimp samples. The recoveries ranged from 75 to 105%. The method was applied to the analysis of farmed freshwater Tilapia fish (Oreochromis niloticus) and shrimp (Penaeus monodon) collected in Sri Lanka. Sulfacetamide (4.31 ± 0.70 µg kg−1) and sulfamethoxypyridazine (0.75 ± 0.15 µg kg−1) were detected in the fish, and sulfapyridine (0.21–0.56 µg kg−1) and sulfadoxine (0.35–1.44 µg kg−1) were detected in the shrimp samples. The concentrations complied with the EU regulation limits for veterinary drug residues in seafood and did not pose a risk in terms of food safety. Full article
(This article belongs to the Section Sustainable Aquaculture)
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12 pages, 2008 KiB  
Article
Exposure of Hyalella bonariensis (Crustacea, Amphipoda) to Essential Oils: Effects on Anesthesia and Swimming Activity
by Alessandra Janaína Becker, Sandro Santos, Berta Maria Heinzmann, Braulio Otomar Caron and Bernardo Baldisserotto
Fishes 2023, 8(3), 149; https://doi.org/10.3390/fishes8030149 - 2 Mar 2023
Cited by 2 | Viewed by 2188
Abstract
Amphipods are frequently used as bioindicators of water quality in experimental or behavior trials. Thus, it is a group considered suitable for use as a model organism in tests with essential oils (EOs). This study evaluated the time required for anesthesia induction and [...] Read more.
Amphipods are frequently used as bioindicators of water quality in experimental or behavior trials. Thus, it is a group considered suitable for use as a model organism in tests with essential oils (EOs). This study evaluated the time required for anesthesia induction and recovery of the amphipod crustacean H. bonariensis exposed to the essential oils of Aloysia triphylla (EOAT) and Lippia alba (EOLA), and their major compounds citral and linalool, respectively. In addition, we evaluated the locomotor activity of amphipods using ANY-maze® software. Mortalities were observed at concentrations of 100 and 200 µL/L of citral (50.0 ± 0.39%) and 750 µL/L of EOLA (66.7 ± 0.33%). Except for linalool, increased concentrations of the compounds of the essential oils decreased the time for sedation and anesthesia induction. There were differences for the induction of anesthesia (p < 0.05) and recovery (p < 0.05) between EOLA and linalool treatments, but not between that for EOAT and citral. Reduced locomotor activity and longer time and episodes of freezing were observed in animals exposed to EOAT. The EOs and their major compounds induced anesthesia and affected the locomotor activity of H. bonariensis, Therefore, EOAT and linalool are recommended for anesthesia of this species. EOAT can also be utilized in long-term exposure. Full article
(This article belongs to the Section Welfare, Health and Disease)
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18 pages, 2359 KiB  
Article
Space and Time Use of European Eel Restocked in Upland Continental Freshwaters, a Long-Term Telemetry Study
by Billy Nzau Matondo, Léa Backory, Guillaume Dupuy, Gildas Amoussou, Ali Abdou Oumarou, Justine Gelder, Séverine Renardy, Jean-Philippe Benitez, Arnaud Dierckx, Frédéric Dumonceau, Xavier Rollin and Michaël Ovidio
Fishes 2023, 8(3), 137; https://doi.org/10.3390/fishes8030137 - 27 Feb 2023
Cited by 3 | Viewed by 2507
Abstract
There is a lack of information on many biological and ecological aspects of the critically endangered European eel during its growth phase in inland waters, such as when the sedentary life stage begins, mobility according to age and response to habitat alteration. We [...] Read more.
There is a lack of information on many biological and ecological aspects of the critically endangered European eel during its growth phase in inland waters, such as when the sedentary life stage begins, mobility according to age and response to habitat alteration. We used mobile radio frequency identification (RFID) telemetry technology to track tagged eels over 6 years after their restocking as glass eels in six typologically different rivers. We also cross-referenced telemetry data with those of several electrofishing monitoring sessions to better understand the mobility and behaviour of eels. The relative abundance (maximum 52 individuals km−1) and detection rate (maximum 28%) of eels were not significantly correlated with the time/age after restocking. Eels were present in all restocked rivers, but their abundance was low and mobility was high in a slightly acidified, oligotrophic river that had experienced a great loss of fish habitat heterogeneity. This loss of habitat heterogeneity was due to flooding events and machinery works in riverbeds to restore the altered riverbanks. Four years after glass eel release, restocked eels became sedentary and moved from shallow to deep microhabitats with riverbeds dominated by blocks as the bottom substrate. After this age, they exhibited high fidelity to the residence site. This study provides new insights concerning the biology and ecology of eels restocked as glass eels in freshwaters, which should lead to improved management plans for the species through the implementation of more effective conservation measures and strategies. Full article
(This article belongs to the Special Issue Advances in Anguillid Eel Biology and Ecology)
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8 pages, 396 KiB  
Article
17β-Estradiol Can Induce Sex Reversal in Brown Trout
by Jill M. Voorhees, Elizabeth R. J. M. Mamer, Daniel J. Schill, Mitchel Adams, Carlos Martinez and Michael E. Barnes
Fishes 2023, 8(2), 103; https://doi.org/10.3390/fishes8020103 - 9 Feb 2023
Cited by 9 | Viewed by 3728
Abstract
Hormones have been used to change phenotypic sex in many fish species. However, information specific to changing sex in brown trout Salmo trutta is lacking. This study compared the effectiveness of two different 17β-estradiol (estradiol) concentrations (20 mg/kg and 30 mg/kg) fed to [...] Read more.
Hormones have been used to change phenotypic sex in many fish species. However, information specific to changing sex in brown trout Salmo trutta is lacking. This study compared the effectiveness of two different 17β-estradiol (estradiol) concentrations (20 mg/kg and 30 mg/kg) fed to brown trout for 60 days, beginning at initial feeding. At 456 days post-initial feeding, the 20 mg/kg and 30 mg/kg treatment groups were 84% and 86% female, respectively. These values were significantly higher than the 47% females observed in the control group which did not receive dietary estradiol. At the end of the 60-day estradiol treatment period, weight gain, percent weight gain, and feed conversion ratio were all significantly lower in the tanks of fish receiving estradiol than in the control tanks. Individual fish fed estradiol also weighed significantly less and were significantly shorter than the fish not receiving estradiol-coated feed. Mortality ranged from 1.0 to 2.4% among the treatments and was not significantly different. After 105 days post-initial feeding, weight gain, percent weight gain, and feed conversion ratio were not significantly different among the treatments. At 456 days post-initial feeding, individual fish were significantly longer and heavier in the 20 mg/kg estradiol treatment compared to the fish in the control treatment, and the fish in the 30 mg/kg estradiol treatment were similar to the other two treatments. This study is the first to document the successful sex reversal of brown trout using estradiol. While the estradiol treatments used in this study did not lead to complete feminization, the observed 85-to-15% female-to-male phenotypic ratio indicates the successful feminization of genetic males. The levels of feminization observed in this study are suitable for this initial step to potentially develop a YY male broodstock to control invasive brown trout populations. Full article
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15 pages, 355 KiB  
Article
Solid-State Fermentation of Distiller’s Dried Grains with Solubles Improves Digestibility for European Seabass (Dicentrarchus labrax) Juveniles
by Diogo Filipe, Mário Dias, Rui Magalhães, Helena Fernandes, José Salgado, Isabel Belo, Aires Oliva-Teles and Helena Peres
Fishes 2023, 8(2), 90; https://doi.org/10.3390/fishes8020090 - 3 Feb 2023
Cited by 14 | Viewed by 3654
Abstract
Aquaculture requires new, economical, and eco-friendly protein sources to replace traditional fisheries and plant ingredients. Using agriculture by-products as protein sources would reduce land-based feed production pressure and waste production, promoting a circular economy and sustainable aquaculture. Distiller’s dried grains with solubles (DDGS) [...] Read more.
Aquaculture requires new, economical, and eco-friendly protein sources to replace traditional fisheries and plant ingredients. Using agriculture by-products as protein sources would reduce land-based feed production pressure and waste production, promoting a circular economy and sustainable aquaculture. Distiller’s dried grains with solubles (DDGS) is the main by-product of bioethanol production. Corn DDGS has a high protein level, but its high fiber content limits its use as a feed ingredient, particularly for carnivorous fish. Solid-state fermentation (SSF) uses lignocellulosic-rich substrates, such as DDGS, for microbial growth in the near absence of water, promoting enzyme production that degrades the lignocellulosic matrix, increasing free reducing sugars, protein, and antioxidant levels of the substrate. In the present work, the SSF of corn DDGS with Aspergillus carbonarius, A. ibericus, and A. uvarum was tested. Then, the digestibility of the most promising fermented DDGS (in terms of upgraded nutritional composition) was tested by including it in a reference diet (70% of a reference diet; 48% crude protein; 15% crude lipids) for European seabass (Dicentrarchus labrax) juveniles (171 g averaged weight; trial duration of 52 days). Among the fungi tested, Aspergillus ibericus led a generally higher upgrading of the DDGS nutritional composition, leading to a high amount of protein (from 42.7 to 49.7 g N/kg DM), phenolic compounds (1.49 to 4.86 mg/g caffeic acid equivalents), free sugars (9.5 to 31.9 mg/g), and enzyme production (45 U/g and 68 U/g of cellulase and xylanase, respectively), and a high reduction in acid detergent fiber and neutral detergent fiber content (up to 29 and 43%, respectively). Compared to the unfermented DDGS, fermented DDGS presented increased protein, lipids, starch, and energy digestibility, while phosphorous digestibility was similar. Compared to the reference diet, dietary inclusion of unfermented or fermented DDGS increased trypsin and chymotrypsin activities. The activity of digestive enzymes was not affected by the inclusion of fermented DDGS, except for amylase activity, which was lower with the fermented DDGS than with the unfermented DDGS diet. In conclusion, SSF of DDGS enhanced its nutritional value, increasing DDGS digestibility when included in diets for European seabass juveniles. Full article
(This article belongs to the Section Sustainable Aquaculture)
33 pages, 5864 KiB  
Article
Morpho-Molecular Discordance? Re-Approaching Systematics of Cambeva (Siluriformes: Trichomycteridae) from the Guaratuba-Babitonga-Itapocu Area, Southern Brazil
by Wilson J. E. M. Costa, Caio R. M. Feltrin, José Leonardo O. Mattos, Roger H. Dalcin, Vinicius Abilhoa and Axel M. Katz
Fishes 2023, 8(2), 63; https://doi.org/10.3390/fishes8020063 - 20 Jan 2023
Cited by 8 | Viewed by 2541
Abstract
A recent field inventory focusing on catfishes of the trichomycterine genus Cambeva detected the occurrence of two morphotypes, C. barbosae and C. cubataonis, in the Guaratuba-Babitonga-Itapocu area (GBIA) of southern Brazil, reporting some discordance with results of coalescent-based approaches for species delimitation [...] Read more.
A recent field inventory focusing on catfishes of the trichomycterine genus Cambeva detected the occurrence of two morphotypes, C. barbosae and C. cubataonis, in the Guaratuba-Babitonga-Itapocu area (GBIA) of southern Brazil, reporting some discordance with results of coalescent-based approaches for species delimitation that indicated different estimates of species number. Contrastingly, based on examination of characters taken from the external morphology and osteology, we here recognised six species of Cambeva in GBIA: C. cf. botuvera, a polymorphic and geographically widespread species; C. cubataonis, endemic to the Rio Cubatão do Norte; and four new species, two endemic to the Rio Itapocu basin, one endemic to the Baía de Babitonga system and one endemic to the Baía de Guaratuba system. We performed a molecular phylogenetic analysis indicating that Cambeva comprises three major clades, the alpha-, beta- and gama-clades, with C. cf. botuvera and a clade comprising C. cubataonis and three new species belonging to the beta-clade and another new species belonging to the gama-clade. We concluded that species here recognised are not in fact incongruent with results of that recent study when taxa are correctly identified by a representative sample of morphological characters, highlighting the importance of osteological characters for delimiting trichomycterine species. Full article
(This article belongs to the Special Issue Featured Papers in Taxonomy, Evolution, and Biogeography Section)
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14 pages, 2656 KiB  
Article
The Effect of Food Deprivation on Foraging Behavior and Digestive and Metabolic Capacities of the Chinese Mitten Crab, Eriocheir sinensis
by Qiaolin Long, Jian Liu, Yunfei Sun, Zhigang Yang, Boping Tang and Yongxu Cheng
Fishes 2023, 8(1), 47; https://doi.org/10.3390/fishes8010047 - 11 Jan 2023
Cited by 3 | Viewed by 2382
Abstract
Food deprivation is a common stress in crustaceans that can affect their behavior and physiology. In this study, a video recording analysis system was used to compare the predation rate and behavior of the Chinese mitten crab, Eriocheir sinensis, foraging on the [...] Read more.
Food deprivation is a common stress in crustaceans that can affect their behavior and physiology. In this study, a video recording analysis system was used to compare the predation rate and behavior of the Chinese mitten crab, Eriocheir sinensis, foraging on the freshwater snail, Bellamya quadrata, under different degrees of food deprivation. The activities of lactate dehydrogenase, α-amylase, pepsin, and lipase in the hepatopancreas of crabs were determined after food deprivation for 0, 3, 9, and 15 days. The results showed that the predation and encounter rates of E. sinensis increased and then decreased with an increase in food deprivation time. The proportion of stationary time of E. sinensis initially decreased and then increased, whereas the proportion of searching and handling time increased initially and then decreased. There was a significant difference in the probability of capture upon encountering; however, food deprivation did not significantly affect the probability of consumption upon capture. Under food deprivation, the proportion of E. sinensis crushing tactics after nine-day food deprivation was significantly lower than that in the first nine days. Lactate dehydrogenase activity in the E. sinensis hepatopancreas after food deprivation was significantly higher than that in those not subjected to food deprivation, and the activities of α-amylase and pepsin in the hepatopancreas were consistent with the predation rate trend, showing an initial increase followed by a decrease. In conclusion, different degrees of food deprivation significantly affected the predation cycle of E. sinensis on B. quadrata. These results lay a solid foundation for further studies on the foraging behavioral ecology of E. sinensis and provide important information for improving E. sinensis production. Full article
(This article belongs to the Special Issue Recent Advances in Crab Aquaculture)
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12 pages, 3215 KiB  
Article
Towards the Control of the Reproduction of the Yellow Clam Amarilladesma mactroides (Reeve, 1854) in Captivity: Effects of Different Stimuli on the Spawning of Laboratory-Conditioned and Unconditioned Breeders
by Nathália Byrro Gauthier, Filipe Scavone Góes, Virgínia Fonseca Pedrosa, Fábio Roselet, Luis Alberto Romano and Ronaldo Olivera Cavalli
Fishes 2023, 8(1), 37; https://doi.org/10.3390/fishes8010037 - 4 Jan 2023
Cited by 1 | Viewed by 2271
Abstract
The effects of temperature manipulation, addition of sperm solution, and exposure to alkalized pH and/or hydrogen peroxide (H2O2) as possible spawning inducers in laboratory-conditioned and unconditioned adults of the yellow clam (Amarilladesma mactroides) were evaluated. In three [...] Read more.
The effects of temperature manipulation, addition of sperm solution, and exposure to alkalized pH and/or hydrogen peroxide (H2O2) as possible spawning inducers in laboratory-conditioned and unconditioned adults of the yellow clam (Amarilladesma mactroides) were evaluated. In three trials, clams were laboratory-conditioned for 14 days and exposed to thermal shocks (from 20 °C to 23–29 °C), while clams from three additional trials were not conditioned but acclimatized for 45 min before spawning induction. Although conditioning advanced gonad maturity and increased the condition factor, none of the thermal treatments triggered spawning in these first trials. Histological analysis indicated that the gonads of conditioned clams were not mature. Alternatively, unfertilized and fertilized eggs, and larvae were observed after unconditioned clams were induced to spawn. The gonads of unconditioned clams were in an advanced stage of maturity. Exposure to temperature shocks, alone or in combination with the addition of sperm solution and with H2O2, resulted in spawning. Clams exposed to H2O2 kept their valves closed and had a high mortality rate. Temperature manipulation is the most promising stimulus to induce spawning in A. mactroides. As the success of conditioning depends on the stage of gonadal development at the time of capture in the wild, a period longer than 14 days may be necessary. Full article
(This article belongs to the Section Sustainable Aquaculture)
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34 pages, 1690 KiB  
Review
Success of Aquaculture Industry with New Insights of Using Insects as Feed: A Review
by Amna Hameed, Waqar Majeed, Muhammad Naveed, Uzma Ramzan, Matteo Bordiga, Maryam Hameed, Saud Ur Rehman and Naureen Rana
Fishes 2022, 7(6), 395; https://doi.org/10.3390/fishes7060395 - 17 Dec 2022
Cited by 18 | Viewed by 8243
Abstract
Most of world’s fish and seafood are produced by aquaculture, which is one of the biggest contributors to the world’s food security. The substantial increase in prices of conventional feed ingredients and the over-exploitation of natural resources are some of the biggest constraints [...] Read more.
Most of world’s fish and seafood are produced by aquaculture, which is one of the biggest contributors to the world’s food security. The substantial increase in prices of conventional feed ingredients and the over-exploitation of natural resources are some of the biggest constraints to aquaculture production. To overcome this stress, different approaches and techniques are used, among which the use of non-conventional feed ingredients in the aquaculture sector is the most recent approach. Different non-conventional feed ingredients such as plant-based products, algae (both micro and macroalgae), single-cell protein (bacteria and yeast), and insect meal are currently used in aquaculture for sustainable food production. Amongst all these novel ingredients, insects have greater potential to replace fishmeal. The existence of about 1.3 billion tons of food and agriculture waste from the food chain supply poses a serious environmental threat. Insects are tiny creatures that can thrive on organic waste and thus can convert the waste to wealth by the bioconversion and nutritional upcycling of organic waste. Insects have the potential to recover nutrients from waste aquaculture products, and many fish species feed on insects naturally. Therefore, employing insects in the aquaculture sector to replace fishmeal is an eco-friendly approach. The present review briefly highlights emerging non-conventional feed ingredients, with special attention given to insects. The current review also focuses on the nutritional value of insects, factors affecting the nutritional value of insects, potential insects that can be employed in the aquaculture sector, the physiological response of fish when fed with insect meal, techno-functional properties of insect meal, and emerging approaches for addressing possible downsides of employing insect meal in fish diets. Finally, it suggests avenues for further research into these inventive fishmeal replacements. Full article
(This article belongs to the Special Issue Fish Nutrition and Feed Technology)
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23 pages, 3620 KiB  
Article
Disentangling Environmental, Economic, and Technological Factors Driving Scallop (Argopecten purpuratus) Aquaculture in Chile
by José Bakit, Gonzalo Álvarez, Patricio A. Díaz, Eduardo Uribe, Rodrigo Sfeir, Sebastian Villasante, Tomas Gabriel Bas, Germán Lira, Hernán Pérez, Andrés Hurtado, Raúl González-Ávalos and Jose Castillo-Venenciano
Fishes 2022, 7(6), 380; https://doi.org/10.3390/fishes7060380 - 8 Dec 2022
Cited by 15 | Viewed by 3870
Abstract
The boom-and-bust trajectory of the Argopecten purpuratus industry in Chile shows the progression from resource extraction (fishing) to production (aquaculture). This paper analyses the effects of environmental, economic, and scientific–technological factors. The influence of each factor on scallop production in Chile was reviewed [...] Read more.
The boom-and-bust trajectory of the Argopecten purpuratus industry in Chile shows the progression from resource extraction (fishing) to production (aquaculture). This paper analyses the effects of environmental, economic, and scientific–technological factors. The influence of each factor on scallop production in Chile was reviewed for the period between the 1980s and 2020. The evaluation of the effects allows the visualisation of the industry’s productive evolution and reveals the current challenges. The occurrence of abrupt environmental disturbances, commercialisation under imperfect market configurations, and public and private efforts in scientific and technological advances have acted favourably on scallop production. However, an industry mainly focused on prices and high production volumes did not devote much effort to develop low-cost climate-resilient technologies. Today, economic challenges must be addressed by helping to reduce production costs and add economic value to products and by-products. Our results show that the industry must focus on low-cost technologies, the use of renewable energy, and the circularity of its processes. The environment ensures the capture of natural seeds and their adaptation to climate change. These challenges must not lose sight of the emerging effects of the COVID-19 pandemic. Full article
(This article belongs to the Special Issue Aquaculture Economics and Fisheries Management)
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17 pages, 2757 KiB  
Article
Untargeted Metabolomics Associated with Behavioral and Toxicological Studies Yield Insights into the Impact of 2,6-Dichloro-3-hydroxy-1,4-benzoquinone Disinfection By-Product on Zebrafish Larvae
by Ieremias Chousidis, Theodoros Chatzimitakos, Constantine Stalikas and Ioannis Leonardos
Fishes 2022, 7(6), 368; https://doi.org/10.3390/fishes7060368 - 2 Dec 2022
Cited by 2 | Viewed by 2210
Abstract
The disinfection by-product 2,6-dichloro-3-hydroxy-1,4-benzoquinone (2,6-DCBQ-OH) is a halobenzoquinone that emerges after chlorination. Therefore, it will inevitably come into contact with aquatic organisms. The aim of this study was to investigate the effect of 2,6-DCBQ-OH on zebrafish embryos. The dose-dependent toxicity was recorded, and [...] Read more.
The disinfection by-product 2,6-dichloro-3-hydroxy-1,4-benzoquinone (2,6-DCBQ-OH) is a halobenzoquinone that emerges after chlorination. Therefore, it will inevitably come into contact with aquatic organisms. The aim of this study was to investigate the effect of 2,6-DCBQ-OH on zebrafish embryos. The dose-dependent toxicity was recorded, and the LC50 value was found to be 186 μg/L. Toxicity was accompanied with morphological, developmental, and behavioral abnormalities, and metabolic alterations. The association of phenotypic alterations with metabolic alterations was investigated through metabolomic study. In the control group, 25 metabolic pathways were identified, and 10 of them remained unaffected upon exposure to the halobenzoquinone. The upregulation of the glutathione pathway suggested that 2,6-DCBQ-OH can cause oxidative stress. In addition, the upregulation of the β-alanine metabolism pathway may be associated with the observed reduced swimming activity observed. Likewise, the downregulation of pathways associated with glycerophospholipids and butyrate can result in endocrine disruption, ineffective regulation of weight and body composition, and glucose homeostasis. The fatty acid elongation and synthesis of essential amino acids are downregulated, which can be associated with insufficient organogenesis at early life stages. In conclusion, exposure of zebrafish to 2,6-DCBQ-OH results in dysregulation and metabolic collapse of the organism, which ultimately result in developmental, morphological, behavioral, and other abnormalities. Full article
(This article belongs to the Special Issue Omics in Fish Aquaculture and Fisheries)
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18 pages, 1632 KiB  
Article
Validation of a Portable eDNA Detection Kit for Invasive Carps
by Stacie A. Kageyama, Matthew R. Hoogland, Tariq Tajjioui, Theresa M. Schreier, Richard A. Erickson and Christopher M. Merkes
Fishes 2022, 7(6), 363; https://doi.org/10.3390/fishes7060363 - 30 Nov 2022
Cited by 10 | Viewed by 4582
Abstract
Loop-mediated isothermal amplification (LAMP) is a rapid molecular detection technique that has been used as a diagnostic tool for detecting human and animal pathogens for over 20 years and is promising for detecting environmental DNA shed by invasive species. We designed a LAMP [...] Read more.
Loop-mediated isothermal amplification (LAMP) is a rapid molecular detection technique that has been used as a diagnostic tool for detecting human and animal pathogens for over 20 years and is promising for detecting environmental DNA shed by invasive species. We designed a LAMP assay to detect the invasive carps, silver carp (Hypophthalmichthys molitrix), bighead carp (Hypophthalmichthys nobilis), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella). To determine the sensitivity of the LAMP assay, we determined limit of detection (LOD) for each invasive carp species and compared with the performance of a grass carp quantitative PCR (qPCR) assay in LOD and in a mesocosm study. We used two grass carp densities, 3 juvenile grass carp in one mesocosm and 33 juvenile grass carp in the other. Prior to adding grass carp to the mesocosms, we added 68 kg of fathead minnows (Pimephales promelas) to each mesocosm to simulate farm ponds used for raising bait fish. We filtered 500 mL of water per sample to compare LAMP and qPCR analysis, and we collected 50 mL grab samples that were only analyzed using qPCR to gain additional data using a higher-throughput method to monitor environmental DNA (eDNA) levels throughout the study period. No eDNA for any of the four invasive carp species was detected in water collected from the mesocosms during the three days prior to adding grass carp. Forty-eight hours after grass carp addition to mesocosms, we detected grass carp eDNA in the mesocosm containing 33 grass carp using the LAMP assay. However, we failed to detect any grass carp DNA in the mesocosm containing 3 grass carp with the LAMP assay throughout the study. We analyzed the data using an occupancy model and found that the 500 mL filter samples yielded a higher eDNA capture probability than 50 mL grab samples in the mesocosm containing three grass carp but had similar eDNA capture probability in the mesocosm containing 33 grass carp. Both LAMP and qPCR reliably detected grass carp eDNA 2 days after grass carp addition, but detections were more consistent with qPCR. The LAMP assay may have utility for certain niche uses because it can be used to rapidly analyze eDNA samples and is robust to inhibition, despite having some limitations. Full article
(This article belongs to the Special Issue Application of Environmental DNA Technology in Fishery Resources)
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22 pages, 4175 KiB  
Article
Elevated Winter Stream Temperatures below Wastewater Treatment Plants Shift Reproductive Development of Female Johnny Darter Etheostoma nigrum: A Field and Histologic Approach
by Catherine M. Adams, Dana L. Winkelman, Paula A. Schaffer, Daniel L. Villeneuve, Jenna E. Cavallin, Michael Ellman, Kelvin Santana Rodriguez and Ryan M. Fitzpatrick
Fishes 2022, 7(6), 361; https://doi.org/10.3390/fishes7060361 - 29 Nov 2022
Cited by 3 | Viewed by 3184
Abstract
River water temperatures are increasing globally, particularly in urban systems. In winter, wastewater treatment plant (WWTP) effluent inputs are of particular concern because they increase water temperatures from near freezing to ~7–15 °C. Recent laboratory studies suggest that warm overwinter temperatures impact the [...] Read more.
River water temperatures are increasing globally, particularly in urban systems. In winter, wastewater treatment plant (WWTP) effluent inputs are of particular concern because they increase water temperatures from near freezing to ~7–15 °C. Recent laboratory studies suggest that warm overwinter temperatures impact the reproductive timing of some fishes. To evaluate winter water temperature’s influence in the wild, we sampled Johnny Darter Etheostoma nigrum from three urban South Platte River tributaries in Colorado upstream and downstream of WWTP effluent discharge sites. Fish were collected weekly during the spring spawning season of 2021 and reproductive development was determined from histological analysis of the gonads. Winter water temperatures were approximately 5–10 °C greater ~300 m downstream of the WWTP effluent compared to upstream sites, and approximately 3 °C warmer at sampling sites ~5000 m downstream of the effluent discharge. Females collected downstream of WWTP effluent experienced accelerated reproductive development compared to upstream by 1–2 weeks. Water quality, including total estrogenicity, and spring water temperatures did not appear to explain varying reproductive development. It appears that small increases in winter water temperature influence the reproductive timing in E. nigrum. Further investigations into how shifts in reproductive timing influence other population dynamics are warranted. Full article
(This article belongs to the Section Biology and Ecology)
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14 pages, 1743 KiB  
Article
Influence of Thermal Regimes on the Relationship between Parasitic Load and Body Condition in European Sardine along the Catalan Coast
by Xènia Frigola-Tepe, Marta Caballero-Huertas, Jordi Viñas and Marta Muñoz
Fishes 2022, 7(6), 358; https://doi.org/10.3390/fishes7060358 - 28 Nov 2022
Cited by 8 | Viewed by 2326
Abstract
The small pelagic European sardine presents high commercial and ecological values. Due to its cold-temperate water affinity, stocks are affected by global warming. Water temperature rise may change primary productivity patterns, negatively affecting fish condition and increasing parasite incidence. In this context, sardine [...] Read more.
The small pelagic European sardine presents high commercial and ecological values. Due to its cold-temperate water affinity, stocks are affected by global warming. Water temperature rise may change primary productivity patterns, negatively affecting fish condition and increasing parasite incidence. In this context, sardine health status was evaluated through the annual cycle on the Catalan Coast using thermal regimes comparison. Morphogravimetric parameters, sex and gonadal stages were assessed; infection by nematodes was characterised, and body condition was estimated by the Le Cren Factor and lipid content measured using a fish fat meter. Significant statistical differences were observed in spawning dynamics, body condition, and parasite infection between thermal regimes. Sardines from the colder north area had better condition and an earlier spawning, with lower parasite incidence (in terms of total prevalence, mean intensity and abundance) than those from the southern coast. Hysterothylacium spp. was the most abundant nematode, while Anisakis spp. prevalence was null in the two locations. Seasonal differences in nematode load were observed along the Catalan Coast, with lower prevalence during the summer and higher in winter-spring. Although previous studies have underestimated parasite influence on sardine health status, parasite abundance and sardine condition were negatively correlated. Seawater temperature and primary productivity are the proposed factors promoting differentiation in nematode infection and fish condition throughout the annual cycle and between locations. Full article
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24 pages, 434 KiB  
Review
Lamiaceae as Feed Additives in Fish Aquaculture
by Graziella Orso, Roberta Imperatore, Elena Coccia, Ghasem Ashouri and Marina Paolucci
Fishes 2022, 7(6), 349; https://doi.org/10.3390/fishes7060349 - 26 Nov 2022
Cited by 12 | Viewed by 4595
Abstract
The growing demand for high-quality food has induced a rapid expansion of the aquaculture sector. On the other hand, this sector has to overcome numerous challenges and problems triggered by the adoption of intensive farming systems, such as stress and high susceptibility to [...] Read more.
The growing demand for high-quality food has induced a rapid expansion of the aquaculture sector. On the other hand, this sector has to overcome numerous challenges and problems triggered by the adoption of intensive farming systems, such as stress and high susceptibility to diseases. The improper use of chemicals and antibiotics has led to the development of antibiotic resistance in fish, with consequent health risks for consumers. Natural additives are increasingly used in aquaculture and, among these, medicinal plants are constantly under investigation as safe and environmentally friendly alternatives to chemicals. Great attention has been paid to Lamiaceae plants as feed additives capable of enhancing the growth performance, immune system, and antioxidant status of farmed fish. The aim of this review is to provide an updated picture of the employment of the Lamiaceae species (oregano, rosemary, sage, thyme, and mint) to enhance farmed fish health. The benefits of oregano, rosemary, sage, thyme, and mint feed supplementation on growth performance, immune system, antioxidant status, hemato-biochemical parameters, and resistance to stress, parasites, and bacteria have been described, highlighting weaknesses and drawbacks and proposing possible implementations. Full article
(This article belongs to the Special Issue Fish Nutrition and Feed Technology)
26 pages, 848 KiB  
Review
A Review on the Use of Computer Vision and Artificial Intelligence for Fish Recognition, Monitoring, and Management
by Jayme Garcia Arnal Barbedo
Fishes 2022, 7(6), 335; https://doi.org/10.3390/fishes7060335 - 17 Nov 2022
Cited by 50 | Viewed by 9669
Abstract
Computer vision has been applied to fish recognition for at least three decades. With the inception of deep learning techniques in the early 2010s, the use of digital images grew strongly, and this trend is likely to continue. As the number of articles [...] Read more.
Computer vision has been applied to fish recognition for at least three decades. With the inception of deep learning techniques in the early 2010s, the use of digital images grew strongly, and this trend is likely to continue. As the number of articles published grows, it becomes harder to keep track of the current state of the art and to determine the best course of action for new studies. In this context, this article characterizes the current state of the art by identifying the main studies on the subject and briefly describing their approach. In contrast with most previous reviews related to technology applied to fish recognition, monitoring, and management, rather than providing a detailed overview of the techniques being proposed, this work focuses heavily on the main challenges and research gaps that still remain. Emphasis is given to prevalent weaknesses that prevent more widespread use of this type of technology in practical operations under real-world conditions. Some possible solutions and potential directions for future research are suggested, as an effort to bring the techniques developed in the academy closer to meeting the requirements found in practice. Full article
(This article belongs to the Section Fishery Facilities, Equipment, and Information Technology)
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