The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation

Topic Information

Dear Colleagues,

Aquatic ecosystems are now facing diverse pressures under the background of climate change and human activities, which bring severe uncertainty to aquaculture sustainability, fisheries management, and biodiversity conservation. It is of vital importance to comprehensively elucidate the responses of aquatic organisms to these global change factors. One of the most critical characteristics of animals, when they cope with changes, is altering their behavioral tactics and physiological processes; however, there seems to be an underestimate of these phenotypic reactions in the contexts of aquaculture, fisheries, and conservation. How to integrate fish phenotype into adaptive management of aquatic ecosystems is one of the crucial topics that has received increasing attention from scientists, decision-makers, and the public in recent years. This Topic plans to give an overview of recent advances in the field of fish phenotype-based adaptive management of aquatic ecosystems. The phenotype involves behaviors and physiology. The important roles of phenotype may be reflected by (a) applying fish behaviors to evaluate welfare status, (b) developing practical methods to decrease undesired behaviors (e.g., cannibalism) in the aquaculture context and to improve fish ecological fitness in stock enhancement and conservation projects, and (c) elucidating the dynamics and mechanisms of fish responses to ecological changes. This Topic welcomes all types of articles.

Dr. Zonghang Zhang
Prof. Dr. Xiumei Zhang
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Animals animals	2.7	5.2	2011	17.7 Days	CHF 2400	Submit
Aquaculture Journal aquacj	-	-	2021	16.3 Days	CHF 1000	Submit
Biology biology	3.5	7.4	2012	17.4 Days	CHF 2700	Submit
Fishes fishes	2.4	3.0	2016	20.9 Days	CHF 2600	Submit
Hydrobiology hydrobiology	-	3.7	2022	30.8 Days	CHF 1000	Submit

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Published Papers (9 papers)

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17 pages, 2766 KiB  

Open AccessArticle

Dietary Astragalus Polysaccharides Can Improve the Immune Capacity and Reproductive Performance of the Lined Seahorse (Hippocampus erectus)

by Siping Li, Xin Liu, Tingting Lin, Yuanhao Ren, Dong Zhang and Keji Jiang

Biology 2025, 14(7), 767; https://doi.org/10.3390/biology14070767 - 25 Jun 2025

Viewed by 210

Abstract

Seahorse (Hippocampus spp.) is popular in the markets of traditional Chinese medicine, aquarium, and curio. In order to protect wild stocks and still meet the market demand, China attempted the large-scale cultivation of seahorses in the early 21st century and achieved it [...] Read more.

Seahorse (Hippocampus spp.) is popular in the markets of traditional Chinese medicine, aquarium, and curio. In order to protect wild stocks and still meet the market demand, China attempted the large-scale cultivation of seahorses in the early 21st century and achieved it in the 2010s. However, in recent years, two new issues have gradually emerged in Chinese seahorse cultivation. One is that the juveniles are prone to disease during diet conversion, and the other is that the reproductive performance of broodstocks is significantly reduced. With the aim to provide some measures that can alleviate these issues, in the present study, we used lined seahorse (Hippocampus erectus, a species widely cultured in China) as the experimental subject and Astragalus polysaccharides (APSs) as the immunostimulant to test whether APSs could improve the immune-health status and reproductive performance of seahorses. The measured indices for reproductive performance included ovarian lipid content, assessment time required before mating for paired male and female seahorses, mating success rate, brood size, and newborn body height. The results showed that for juveniles during diet conversion, their body weight, survival rate, plasma immunocytokine contents (interleukin-2, interferon-α, and immunoglobulin M), and alpha diversity indices (Simpson and Pielou’s-e) of the intestinal microbiota were significantly higher than those of the control group after dietary APSs. For broodstocks, compared with the control group, the expression of lipid substances in the ovary was significantly upregulated, the assessment time was significantly shortened, and the body height of their newborns was significantly increased in the APS group. These results demonstrate that APSs could indeed improve the immune-health status and reproductive performance of seahorses, providing guidance for addressing existing issues in seahorse cultivation. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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19 pages, 4708 KiB  

Open AccessArticle

YOLOv8-BaitScan: A Lightweight and Robust Framework for Accurate Bait Detection and Counting in Aquaculture

by Jian Li, Zehao Zhang, Yanan Wei and Tan Wang

Fishes 2025, 10(6), 294; https://doi.org/10.3390/fishes10060294 - 17 Jun 2025

Viewed by 260

Abstract

Excessive bait wastage is a major issue in aquaculture, leading to higher farming costs, economic losses, and water pollution caused by bacterial growth from unremoved residual bait. To address this problem, we propose a bait residue detection and counting model named YOLOv8-BaitScan, based [...] Read more.

Excessive bait wastage is a major issue in aquaculture, leading to higher farming costs, economic losses, and water pollution caused by bacterial growth from unremoved residual bait. To address this problem, we propose a bait residue detection and counting model named YOLOv8-BaitScan, based on an improved YOLO architecture. The key innovations are as follows: (1) By incorporating the channel prior convolutional attention (CPCA) into the final layer of the backbone, the model efficiently extracts spatial relationships and dynamically allocates weights across the channel and spatial dimensions. (2) The minimum points distance intersection over union (MPDIoU) loss function improves the model’s localization accuracy for bait bounding boxes. (3) The structure of the Neck network is optimized by adding a tiny-target detection layer, which improves the recall rate for small, distant bait targets and significantly reduces the miss rate. (4) We design the lightweight detection head named Detect-Efficient, incorporating the GhostConv and C2f-GDC module into the network to effectively reduce the overall number of parameters and computational cost of the model. The experimental results show that YOLOv8-BaitScan achieves strong performance across key metrics: The recall rate increased from 60.8% to 94.4%, mAP@50 rose from 80.1% to 97.1%, and the model’s number of parameters and computational load were reduced by 55.7% and 54.3%, respectively. The model significantly improves the accuracy and real-time detection capabilities for underwater bait and is more suitable for real-world aquaculture applications, providing technical support to achieve both economic and ecological benefits. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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31 pages, 1713 KiB  

Open AccessReview

Aquatic Organisms in Response to Salinity Stress: Ecological Impacts, Adaptive Mechanisms, and Resilience Strategies

by Tariq Dildar, Wenxiao Cui, Mhd Ikhwanuddin and Hongyu Ma

Biology 2025, 14(6), 667; https://doi.org/10.3390/biology14060667 - 9 Jun 2025

Viewed by 691

Abstract

Salinity stress presents a major ecological challenge for aquatic organisms, particularly in environments where salinity levels fluctuate. These fluctuations are becoming more pronounced due to climate change, further destabilizing aquatic ecosystems. Understanding how organisms adapt to such variability is essential for biodiversity conservation [...] Read more.

Salinity stress presents a major ecological challenge for aquatic organisms, particularly in environments where salinity levels fluctuate. These fluctuations are becoming more pronounced due to climate change, further destabilizing aquatic ecosystems. Understanding how organisms adapt to such variability is essential for biodiversity conservation and the sustainable management of aquatic resources. This review examines the physiological, molecular, and behavioral adaptations that enable aquatic organisms to survive and thrive under salinity stress. Specifically, it explores mechanisms of osmotic regulation, ion transport, and oxidative stress responses, highlighting key signaling pathways—such as AMP-activated protein kinase (AMPK), Phosphatidylinositol 3-kinase–protein kinase (PI3K-AKT), Mitogen-activated protein kinase (MAPK), and the Hippo pathway—that facilitate these adaptive processes. The review also emphasizes the genetic and epigenetic modifications that contribute to resilience, underscoring the importance of genetic diversity for species survival in fluctuating salinity conditions. Furthermore, the interactions between host organisms and their microbiomes are discussed as critical factors influencing resilience. The review addresses the impact of salinity fluctuations on species distribution and biodiversity, with a focus on the implications of climate change for aquatic ecosystems. Finally, strategies for mitigating salinity stress, such as nutritional interventions and the development of salinity-resistant varieties, are explored, particularly in aquaculture. Overall, this review consolidates current knowledge on organismal adaptations, molecular mechanisms, and environmental challenges, offering valuable insights for ecological research and aquaculture practices in the face of climate change. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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16 pages, 1344 KiB  

Open AccessArticle

Sexual Selection in Mosquitofish: Differences in the Use of Mating Cues Between Sexes

by Jiefei Wei, Bowen Feng, Chenglong Dong, Bojian Chen and Kai Liu

Animals 2025, 15(10), 1489; https://doi.org/10.3390/ani15101489 - 21 May 2025

Viewed by 272

Abstract

Sexual selection is a major driver of speciation and evolution, with mate choice being a key component. Individuals assess mate quality by integrating various mating cues. The Western mosquitofish (Gambusia affinis), a species exhibiting pronounced sexual dimorphism in body size and [...] Read more.

Sexual selection is a major driver of speciation and evolution, with mate choice being a key component. Individuals assess mate quality by integrating various mating cues. The Western mosquitofish (Gambusia affinis), a species exhibiting pronounced sexual dimorphism in body size and secondary sexual traits, serves as an ideal model for studying mate choice. This study examines the impact of mating cues on mate choice in different sexes of G. affinis through a combination of morphological parameter database construction, computer-simulated animations, and dichotomous association preference tests. The results showed that male gonopodium status significantly affects female mate choice. Females exhibited a preference for males with resting-phase gonopodia, suggesting their aversion to forced copulation and sexual harassment in coercive mating systems. Furthermore, males preferred younger females, with this preference being positively correlated with male body size. This suggests that males are sensitive to sperm competition intensity and may base their choice on social rank. Geometric morphometric analysis and simulation experiments showed that males preferred females with larger gravid spots, regardless of age, suggesting that gravid spot size reflects female fecundity. Male preference for younger females with streamlined bodies and smaller abdomens was significant, but body size did not affect mate choice in general. Our findings highlight that female and male G. affinis employ different mate choice strategies, with females prioritizing male harassment avoidance and males considering multiple mating cues, not solely one dominant characteristic, in their mate choice decisions. These findings demonstrate that mate choice in G. affinis involves balancing conflicting preferences for traits associated with reduced harassment risk (e.g., resting-phase gonopodium in males) and those linked to reproductive potential (e.g., large gravid spot in females), highlighting the nuanced decision-making processes in both sexes. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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13 pages, 1659 KiB  

Open AccessArticle

7,8-DHF Modulates Aggressive Behavior in Sebastes schlegelii: Phenotype-Dependent Responses in Aggression-Dimorphic Individuals

by Shufei Xu, Xinna Ma, Yang Xiao, Tao Zhang, Chao Ma and Zhen Ma

Animals 2025, 15(10), 1463; https://doi.org/10.3390/ani15101463 - 19 May 2025

Viewed by 316

Abstract

Aggressive behavior is regulated by intricate neural circuits and molecular mechanisms, notably through the interaction of brain-derived neurotrophic factor (BDNF) with its receptor, tropomyosin receptor kinase B (TrkB), which influences neuroplasticity and related behavioral phenotypes. We investigate the role of the BDNF signaling [...] Read more.

Aggressive behavior is regulated by intricate neural circuits and molecular mechanisms, notably through the interaction of brain-derived neurotrophic factor (BDNF) with its receptor, tropomyosin receptor kinase B (TrkB), which influences neuroplasticity and related behavioral phenotypes. We investigate the role of the BDNF signaling pathway in fish aggression using juvenile black rockfish (Sebastes schlegelii), which exhibit distinct aggressive phenotypes. The TrkB agonist 7,8-dihydroxyflavone (7,8-DHF) was administered intraperitoneally at doses of 1.25, 2.5, and 5 mg/kg to assess its effects on the behavioral characteristics of high-aggression (H-agg) and low-aggression (L-agg) phenotypes. Our findings indicate the following: (1) The effects of 7,8-DHF are dose-dependent, with 2.5 mg/kg identified as the effective threshold dose for H-agg individuals; (2) in the H-agg group, this dose significantly reduced locomotor acceleration, angular velocity, and activity frequency, while prolonging the first movement latency; (3) in the L-agg group, only angular velocity was significantly decreased with the 2.5 mg/kg treatment, with no significant changes observed in other behavioral parameters. This study provides the first evidence for differential behavioral responses to 7,8-DHF in S. schlegelii, demonstrating dose-dependent aggression suppression in H-agg phenotypes and threshold-specific responses in L-agg phenotypes. These insights into the neuro-molecular basis of fish aggression can guide phenotype-specific management in aquaculture, potentially improving stress management, reducing injuries and mortality, and boosting productivity. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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11 pages, 2807 KiB  

Open AccessArticle

Study on the Flow Velocity Preference of the Four Major Chinese Carps Using Convolutional Neural Networks

by Ning Qiu, Wenjing Li, Yi Yu, Jianna Jia, Guoqiang Ma and Shitao Peng

Fishes 2025, 10(4), 172; https://doi.org/10.3390/fishes10040172 - 11 Apr 2025

Viewed by 367

Abstract

Flow velocity is a critical factor in determining the suitability of fish habitats. Understanding the preference patterns of the four major Chinese carps (FMCCs) for different flow velocities is crucial for their habitat conservation and restoration. In this study, the preference of individual [...] Read more.

Flow velocity is a critical factor in determining the suitability of fish habitats. Understanding the preference patterns of the four major Chinese carps (FMCCs) for different flow velocities is crucial for their habitat conservation and restoration. In this study, the preference of individual fish species, approximately 15 cm in length, for flow velocity was investigated at flow velocity gradients of 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 times their body length. Additionally, a deep learning algorithm based on convolutional neural networks (CNNs) was employed for fish target detection. The results showed that, at this length, black carp (Mylopharyngodon piceus) preferred fast currents when the inlet flow velocity was between 0.4 and 1.6 times their body length, while grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), and bighead carp (Hypophthalmichthys nobilis) preferred fast currents when the inlet flow velocity of the test flume was between 0.4 and 2.0 times their body length. However, this preference for fast currents decreased as the overall flow velocity increased to a specific threshold, eventually leading to their avoidance. The highest preference for fast currents among the four species was observed at inlet flow velocities of 1.2, 0.4, 0.8, and 0.8 times their body length, respectively. The findings of this study provide important insights into habitat conservation and restoration for the FMCCs in projects focused on the construction of navigation channels and water conservancy. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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13 pages, 1549 KiB  

Open AccessArticle

Boat Noise Increases the Oxygen Consumption Rate of the Captive Juvenile Large Yellow Croaker, Larimichthys crocea

by Ruijie Xu, Shouguo Yang, Yiyu Li, Xuguang Zhang and Xianming Tang

Animals 2025, 15(5), 714; https://doi.org/10.3390/ani15050714 - 2 Mar 2025

Cited by 1 | Viewed by 838

Abstract

Anthropogenic noise pollution is increasingly acknowledged as a major threat to marine ecosystems, especially for sound-sensitive species, such as the large yellow croaker (Larimichthys crocea). While the effects of underwater noise on fish behavior and physiology have been well-documented, its influence [...] Read more.

Anthropogenic noise pollution is increasingly acknowledged as a major threat to marine ecosystems, especially for sound-sensitive species, such as the large yellow croaker (Larimichthys crocea). While the effects of underwater noise on fish behavior and physiology have been well-documented, its influence on oxygen metabolism across varying temperatures remains poorly understood. This study examines the impact of boat noise on the oxygen consumption rate (OCR) of juvenile large yellow croakers at different temperatures, a key factor in their metabolic activity. The underwater noise generated by a fishing boat spans a broad frequency range, with a peak spectrum level of 130 dB re 1 µPa at low frequencies between 100 and 200 Hz. Our findings reveal that boat noise significantly elevates the OCR of juvenile fish, with mass-specific OCR increasing by 65.0%, 35.3%, and 28.9% at 18 °C, 25 °C, and 30 °C, respectively. Similarly, individual OCR rose by 60.7%, 35.3%, and 17.1% at these temperatures. These results demonstrate that boat noise triggers a stress response in fish, resulting in heightened metabolic demands across different seasonal conditions. Notably, the impact of boat noise on respiratory metabolism is most significant at lower temperatures. In aquatic environments with stable oxygen levels, the noise-induced rise in oxygen consumption could lead to hypoxia and provoke maladaptive behavioral changes in fish. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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16 pages, 2956 KiB  

Open AccessArticle

Mate Choice in Western Mosquitofish (Gambusia affinis) in Response to Virtual Mates: A Method for the Investigation of Fish Mate Choice Using Maya 3D Simulation Technology

by Bowen Feng, Liming Chen, Liangmin Huang, Jun Li and Kai Liu

Animals 2024, 14(23), 3369; https://doi.org/10.3390/ani14233369 - 22 Nov 2024

Viewed by 904

Abstract

Visual signals are crucial for animals to obtain information about their environment, and they play a significant role in mate choice. However, individual variability and factors such as movement patterns can hinder research flexibility. A key challenge in this field is the accurate [...] Read more.

Visual signals are crucial for animals to obtain information about their environment, and they play a significant role in mate choice. However, individual variability and factors such as movement patterns can hinder research flexibility. A key challenge in this field is the accurate simulation of specific movements and behaviors. In this study, we investigated the western mosquitofish (Gambusia affinis) by creating 3D simulation animations using the Maya 2018 software. Meanwhile, we validated the effectiveness of this animation through dichotomous association preference tests. The results showed that our subjects could successfully identify 3D simulated mates, and both males and females demonstrated pronounced preferences for larger simulated animations. Moreover, our findings revealed that this species exhibited a notably stronger preference for 3D simulations compared to 2D animations. These findings suggest that 3D simulation technology holds significant potential for the investigation of fish mate choice, offering an efficient, precise, standardized, and easily manageable non-invasive method for future research in fish behavior. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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16 pages, 4867 KiB  

Open AccessArticle

Effects of Stocking Density on the Survival, Growth, and Stress Levels of the Juvenile Lined Seahorse (Hippocampus erectus) in Recirculating Aquaculture Systems

by Tingting Lin, Siping Li, Dong Zhang, Xin Liu and Yuanhao Ren

Biology 2024, 13(10), 807; https://doi.org/10.3390/biology13100807 - 10 Oct 2024

Cited by 2 | Viewed by 1636

Abstract

Seahorses are increasingly regarded as a promising farming object suitable for recirculating aquaculture systems (RASs) due to their high economic value. However, reports on the large-scale farming of seahorses in RASs are rare, and some key parameters, such as stocking densities, are still [...] Read more.

Seahorses are increasingly regarded as a promising farming object suitable for recirculating aquaculture systems (RASs) due to their high economic value. However, reports on the large-scale farming of seahorses in RASs are rare, and some key parameters, such as stocking densities, are still unclear. In the present study, we employed the lined seahorse (Hippocampus erectus), for which large-scale farming has been achieved, to determine the suitable stocking density for three different-sized juveniles in RASs. The three different-sized juveniles had body heights of 4.0, 7.0, and 9.0 cm, and their test density gradients were 1.0, 0.8, 0.6, and 0.4 inds/L; 0.6, 0.5, 0.4, and 0.3 inds/L; and 0.4, 0.3, 0.2, and 0.1 inds/L, respectively. The juveniles were cultivated for one month, and then their survival, growth, and plasma cortisol and brain serotonin contents (two stress-related indicators) were analyzed. The results show that, regardless of the size of the juveniles, a high density can inhibit growth and trigger stress responses. In addition, for small- (4.0 cm) and medium-sized (7.0 cm) juveniles, a high density can also exacerbate size heterogeneity and cause death. Taking into account the welfare and yield of farmed seahorses, the present study suggests that the suitable stocking densities for 4.0, 7.0, and 9.0 cm juveniles in RASs are 0.6, 0.4, and 0.2 inds/L, respectively. Full article

(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)

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