Search Results (1,089)

The whale shark Rhincodon typus is the largest known extant omnivorous fish species, reaching up to 17 m in length. Because of its slow growth and late maturity, R. typus is particularly vulnerable to human activities and is listed as endangered on the IUCN Red List. Understanding its biological characteristics, such as growth rate, is essential for their conservation. Non-invasive methods, including stereo-image measurements, have been used to measure the body length of the species over the years, which aggregates in coastal areas during specific life stages. This method enables us to estimate fish length by recording the target using a stereo camera, which commonly consists of two cameras. However, measurement errors increase in the setup as the target moves away from the camera. Therefore, we conducted a multi-stereo video shoot of a free-swimming whale shark in an aquarium tank and compared the performance of stereo cameras using two, three, and four cameras. The setups with three and four cameras outperformed the traditional two-camera stereo setup in terms of precision and accuracy, suggesting that a multi-stereo camera system can effectively estimate the body length of large animals such as whale sharks from a considerable distance. Full article

Fish barrier technology by pulsed direct current has broad application potential to guide fish to suitable waters. The primary objective of this investigation was to study the effects of electric pulse frequency and water velocity on fish deterrence by pulsed direct current. The test fish were adults of two common carp species, Hypophthalmichthys nobilis (bighead carp, standard length 0.460–0.545 m) and Cyprinus carpio (Eurasian carp, standard length 0.292–0.335 m). Experiments were conducted in the 20 m swimming chamber of a 50 m flume, with a pulsed electric barrier produced by vertical electrodes located in the middle of the swimming chamber. The effectiveness of the electric barrier in deterring fish from swimming upstream past the electrodes was tested. The electric pulse generator produces a square wave pulse, with a voltage of 150 V and width of 2 ms. There were four electric pulse frequency treatments (4 Hz, 6 Hz, 8 Hz, 10 Hz), and two water velocity treatments (0.2 m/s, 0.6 m/s), with 10 replicates of each treatment. There were four primary findings. (1) Of the 160 fish tested, no fish was stunned and only 4 trembled (lost the ability to swim) for more than 2 s after encountering the electric barrier. (2) At a given water velocity, the crossing probability decreased as pulse frequency increased, and the decrease was largest when the frequency increased from 8 to 10 Hz. (3) At a given electric pulse frequency, the crossing probability was higher at the high water velocity, and barrier efficiency was more sensitive to velocity at higher pulse frequencies. (4) H. nobilis, a stronger swimmer, crossed more often than C. carpio. This study can provide ideas for the management of invasive species. However, the study was conducted under controlled laboratory conditions, and field experiments should be carried out before field applications. Full article

This research aimed to evaluate the effect of biofloc technology on the intestinal morphometry, productive performance, and survival of juvenile Mugil cephalus. An 87-day investigation was conducted with two treatments, each with three replicates. Treatment one involved rearing juvenile M. cephalus in a biofloc system with a C/N ratio of 15:1, and treatment two involved rearing juvenile M. cephalus with a water exchange and no carbon addition. Ninety (90) juveniles of Mugil cephalus with an average weight of 117.36 ± 6.48 g were randomly distributed into six (6) circular plastic tanks of 250 L (fifteen fish per tank). At the end of the experiment, 10% of each experimental unit’s population was sacrificed for intestinal morphometry analysis. The productive performance was evaluated every 30 days by randomly sampling fish from each tank for biometric measurements, including the specific growth rate (SGR), feed conversion ratio (FCR), condition factor (K), and survival. No structural changes were observed in the intestinal mucosa. The fish reared in biofloc exhibited a similar gut morphometry (villus length and villus thickness) compared to the fish in the water exchange system. The biofloc system does not compromise the gut health of mullet. No significant differences (p > 0.05) were observed in the final weight, weight gain (WG), daily weight gain (DWG), specific growth rate (SGR), condition factor (K), and survival between the treatments evaluated. M. cephalus can be reared using biofloc technology, demonstrating significant water savings compared to water exchange systems. Full article

The large-eye dentex (Dentex macrophthalmus) is a relatively small sparid fish with increasing potential as a supplementary fishery resource in the Mediterranean Sea, particularly as traditional stocks face overexploitation. Despite its widespread distribution, biological data on this species, especially from Greek waters, remain scarce. This study presents the first comprehensive biological assessment of D. macrophthalmus in the Pagasitikos Gulf, focusing on population structure, growth, mortality, and the application of machine learning (ML) for age prediction. A total of 305 individuals were collected, revealing a female-biased sex ratio and negative allometric growth in both somatic and otolith dimensions. The von Bertalanffy growth parameters indicated a slow growth rate (k = 0.16 year⁻¹), with an estimated asymptotic length (L∞) of 25.97 cm. The population was found to be underexploited (E = 0.41), suggesting resilience to current fishing pressure. Stepwise regression and ML models were employed to predict age from otolith morphometrics. A linear model identified otolith weight and aspect ratio as the most significant predictors of age (R² = 0.8). Among the ML algorithms tested, the Neural Network model achieved the highest performance (R² = 0.764, MAPE = 14.10%), demonstrating its potential for accurate and efficient age estimation. These findings provide crucial baseline data for the sustainable management of D. macrophthalmus and highlight the value of integrating advanced ML techniques into fisheries biology. Full article

Fish species’ biological vocalizations serve as essential acoustic signatures for passive acoustic monitoring (PAM) and ecological assessments. However, limited availability of high-quality acoustic recordings, particularly for region-specific species like the brown croaker (Miichthys miiuy), hampers data-driven bioacoustic methodology development. In this study, we present a framework for reconstructing brown croaker vocalizations by integrating fk14 wavelet synthesis, PSO-based parameter optimization (with an objective combining correlation and normalized MSE), and deep learning-based validation. Sensitivity analysis using a normalized Bartlett processor identified delay and scale (length) as the most critical parameters, defining valid ranges that maintained waveform similarity above 98%. The reconstructed signals matched measured calls in both time and frequency domains, replicating single-pulse morphology, inter-pulse interval (IPI) distributions, and energy spectral density. Validation with a ResNet-18-based Siamese network produced near-unity cosine similarity (~0.9996) between measured and reconstructed signals. Statistical analyses (95% confidence intervals; residual errors) confirmed faithful preservation of SPL values and minor, biologically plausible IPI variations. Under noisy conditions, similarity decreased as SNR dropped, indicating that environmental noise affects reconstruction fidelity. These results demonstrate that the proposed framework can reliably generate acoustically realistic and morphologically consistent fish vocalizations, even under data-limited scenarios. The methodology holds promise for dataset augmentation, PAM applications, and species-specific call simulation. Future work will extend this framework by using reconstructed signals to train generative models (e.g., GANs, WaveNet), enabling scalable synthesis and supporting real-time adaptive modeling in field monitoring. Full article

Structural variation (SV) serves as a fundamental driver of phenotypic diversity and environmental adaptation in plants and animals, significantly influencing key agronomic traits in crops. Common wheat (Triticum aestivum L.), an allohexaploid species, harbors extensive chromosomal SVs and distant hybridization-induced recombination events that provide critical resources for genetic improvement. This study utilizes non-denaturing fluorescence in situ hybridization (ND-FISH) and oligonucleotide multiplex probe-based FISH (ONPM-FISH) to analyze the karyotypes of 153 BC₁F₄–BC₁F₆ lines derived from the hybrid line Xiaoyan 7430 and common wheat Yannong 1212. The results revealed that Xiaoyan 7430 carries 8 alien chromosome pairs and 20 wheat chromosome pairs (lacking 6B), and Yannong 1212 contains 21 pairs of wheat chromosomes. The parental lines exhibited presence/absence variations (PAVs) on chromosomes 2A, 6A, 5B, 1D, and 2D. Chromosomal variations, including numerical chromosomal variation (NCV), structural chromosomal variation (SCV), and complex chromosomal variation (CCV), were detected in the progeny lines through ONPM-FISH analysis. The tracking of alien chromosomes over three consecutive generations revealed a significant decrease in transmission frequency, declining from 61.82% in BC₁F₄ to 26.83% in BC₁F₆. Telosomes were also lost during transmission, declining from 21.82% in BC₁F₄ to 9.76% in BC₁F₆. Alien chromosome 1J^S, 4J, and 6J exhibited the highest transmission stability and were detected across all three generations. Association analysis showed that YN-PAV.2A significantly affected the length/width ratio (LWR) and grain diameter (GD); YN-PAV.6A, XY-PAV.6A, and PAV.5B increased six grain traits (+2.25%~15.36%); YN-PAV.1D negatively affected grain length (GL) and grain circumference (GC); and XY-PAV.2D exerted positive effects on thousand-grain weight (TGW). Alien chromosomes differentially modulated grain characteristics: 1J^S and 6J both reduced grain length and grain circumference; 1J^S increased LWR; and 4J negatively impacted TGW, grain width (GW), GD, and grain area (GA). Meanwhile, increasing alien chromosome numbers correlated with progressively stronger negative effects on grain traits. These findings elucidate the genetic mechanisms underlying wheat chromosomal variations induced by distant hybridization and their impact on wheat grain traits, and provide critical intermediate materials for genome design breeding and marker-assisted selection in wheat improvement. Full article

This work evaluates the effect of raw material and protease enzymes on the antioxidant and antidiabetic potential of fish by-product hydrolysates. For this, mackerel (Scomber scombrus) and sardine (Sardina pilchardus) by-products were hydrolyzed using papain, pepsin, and Protamex^TM. Pepsine produced hydrolysates with a lower degree of hydrolysis (34%) and longer peptide chain lengths (2.9), regardless of the raw material. The highest DH was found for the sardine by-products hydrolyzed with papain and Protamex^TM, exceeding 55% for both enzymes. The mackerel by-product hydrolysates exhibited higher antioxidant activity, while the sardine samples showed more potent antidiabetic effects. Accordingly, sardine by-products and pepsin would be preferable for producing hydrolysates with antidiabetic potential, and mackerel by-products, hydrolyzed papain, and Protamex^TM would be useful for producing antioxidant peptides. This study demonstrates the potential of Atlantic mackerel and sardine waste as a source of bioactive peptides and the opportunity for revalorizing these by-products. Full article

The microbial community in a recirculating aquaculture system (RAS) is pivotal in fish health, contributing significantly to the productive performance during the growing-out phase. Classical and molecular methods using PCR for species-specific amplifications have traditionally been used for bacterial community surveillance. Unfortunately, these approaches mask the real bacterial diversity and abundance, population dynamics, and prevalence of pathogenic bacteria. In this study, we explored the use of Oxford Nanopore Technology to characterize the microbiota and functional metagenomics in a commercial freshwater RAS. Intestine samples from Atlantic salmon (Salmo salar (85 ± 5.7 g)) and water samples from the inlet/outlet water, settling tank, and biofilters were collected. The full-length 16S rRNA gene was sequenced to reconstruct the microbial community, and bioinformatic tools were applied to estimate the functional potential in the RAS and fish microbiota. The analysis showed that bacteria involved in denitrification processes were found in water samples, as well as metabolic pathways related to hydrogen sulfide metabolism. Observations suggested that fish classified as sick exhibited decreased microbial diversity compared with fish without clinical symptomatology (p < 0.05). Proteobacteria were predominant in ill fish, and pathogens of the genera Aeromonas, Aliivibrio, and Vibrio were detected in all intestinal samples. Notably, Aliivibrio wodanis was detected in fish showing abnormal clinical conditions. Healthy salmon showed higher contributions of pathways related to amino acid metabolism and short-chain fatty acid fermentation (p < 0.05), which may indicate more favorable fish conditions. These findings suggest the utility of nanopore sequencing methods in assessing the microbial community in RASs for salmon aquaculture. Full article

Sharks play critical roles in marine ecosystems as apex or mesopredators, regulating trophic dynamics and ecosystem stability. However, their populations are increasingly threatened due to overexploitation caused by targeted fisheries, bycatch, and illegal activities. This study investigates the feeding ecology and reproductive biology of the shark species Mustelus mustelus, which has been heavily fished across the Mediterranean, leading to significant population declines. A total of 333 specimens were collected between October 2019 and October 2022 from Türkiye’s Aegean Sea, Sea of Marmara, and Levantine Sea coasts. The total lengths of the specimens ranged from 42.1 to 173.0 cm, with an average of 73.5 cm ± 26.8, and their weights ranged from 205 to 22,470 g, with an average of 1840.2 g ± 2525.5. Stomach content analyses revealed that M. mustelus is a benthic predator with a broad diet. Regional and size-based comparisons indicated that crustaceans were the primary food source, followed by teleost fish and mollusks. Ontogenetic dietary shifts were evident, with juveniles feeding predominantly on crustaceans, while adults consumed more teleost fish and mollusca. The reproductive biology analysis showed placental viviparity in M. mustelus, with the smallest observed mature male measuring 75 cm TL and the smallest observed pregnant female measuring 96 cm TL. The uterine fecundity of pregnant females ranged from 8 to 29 embryos. Additionally, the pupping season of M. mustelus in the Aegean Sea was found to occur in March and April. M. mustelus populations have declined dramatically in the western Mediterranean and in many other parts of their range. The scarcity of data on this species in the eastern Mediterranean basin, including Türkiye, is noteworthy. Therefore, this study investigated the populations in the study area from a bioecological perspective and provides fundamental data to support the development of conservation strategies for the species. Full article

An experimental study was conducted in the laboratory to investigate the interactive effects of fish and algae on growth patterns and water quality. Body length and body weight of Carassius carassius, Microcystis aeruginosa (M. aeruginosa) density, and concentrations of nutrients were monitored continuously over a period of 92 days. It was noted that fish growth was significantly higher in the absence of M. aeruginosa compared to its presence (p < 0.05). This can be partly attributed to toxin production by M. aeruginosa. The densities and growth rates of M. aeruginosa in groups with Carassius carassius were significantly higher than those in fishless groups (p < 0.05), and this was attributable to fish metabolism and bioturbation, which led to a considerable increase in ammonia and total dissolved nitrogen concentrations, as well as a significant impact on proportions of nutrients. The growth rate of Carassius carassius firstly increased and then decreased with increasing M. aeruginosa densities, and a quantitative relationship was established using the Gompertz equation and Logistic equation (R² = 0.914–0.955). Based on the above results, we concluded that interactions between fish and algae are greatly related to their consequences on water qualities, by employing equations, a more detailed interpretation of the processes occurring in the fish–algae system can be achieved. Full article

Background: Although telomere length maintenance is a common characteristic of hematological malignancies, the role of telomere length as a prognostic factor to stratify acute lymphoblastic leukemia (ALL) patients depending on their risk of relapse remains elusive. Methods: This knowledge gap motivated us to examine telomere length values in children with ALL at the time of diagnosis and after treatment using quantitative polymerase chain reaction (qPCR) (n = 35). To achieve high-resolution precision and cell specificity, a quantitative fluorescence in situ hybridization (qFISH) technique was developed (n = 5). Results: The results demonstrated statistically significant evidence of telomere shortening in the lymphoblasts of children with ALL but not in the lymphocytes of children after remission following treatment. Our findings also suggested a significant association between telomere shortening and a high risk of relapse disease. Last but not least, our preliminary results showed a trend that telomere shortening was more pronounced in children with B-ALL compared to those with T-ALL in a non-significant manner. Conclusions: Consequently, the current study provides preliminary insights into the potentially substantial prognostic value of telomere length in the progression of pediatric ALL, with the possibility of predicting treatment response. To clarify the application of telomere length as a possible biomarker for disease progression and treatment response in children with ALL, the telomere length values of additional participants need to be examined in further studies. Full article

The size and mass of fish are crucial parameters in aquaculture management. However, existing research primarily focuses on conducting fish size and mass estimation under ideal conditions, which limits its application in actual aquaculture scenarios with complex water quality and fluctuating lighting. A non-contact size and mass measurement framework is proposed for complex underwater environments, which integrates the improved FishKP-YOLOv11 module based on YOLOv11, stereo vision technology, and a Random Forest model. This framework fuses the detected 2D key points with binocular stereo technology to reconstruct the 3D key point coordinates. Fish size is computed based on these 3D key points, and a Random Forest model establishes a mapping relationship between size and mass. For validating the performance of the framework, a self-constructed grass carp dataset for key point detection is established. The experimental results indicate that the mean average precision (mAP) of FishKP-YOLOv11 surpasses that of diverse versions of YOLOv5–YOLOv12. The mean absolute errors (MAEs) for length and width estimations are 0.35 cm and 0.10 cm, respectively. The MAE for mass estimations is 2.7 g. Therefore, the proposed framework is well suited for application in actual breeding environments. Full article

Managing invasive species such as the Chinese sleeper (Perccottus glenii) supports the goals of sustainable development by preserving native biodiversity. This study investigated the population structure, growth, and ecological impact of P. glenii in a small, anthropogenically altered tributary of the Vistula River (central Poland). Electrofishing surveys conducted between 2017 and 2023 assessed sex ratio, age structure, body size, condition (Fulton’s index), and growth parameters, as well as changes in the local fish community. The sex ratio was nearly balanced (♀:♂ = 1.00:0.99), and average standard length and weight were 6.54 cm/9.11 g (females) and 6.36 cm/7.69 g (males). Dominant individuals were from age group of 2+ years. The Fulton condition factor ranged from 2.54 to 2.58, while positive algometric growth was observed for both sexes. The von Bertalanffy growth model parameters (L∞ = 175.37 mm, k = 0.104, t₀ = −1.711) revealed slower growth compared to other Eurasian populations. In the individual months of the study, changes in the sex structure, length, weight, and age of the fish were observed. This seasonality may have resulted from physiological changes (including fish growth and reproductive processes), their migration, and environmental changes, such as food availability and hydrochemical parameters, occurring during this period. Additionally, over the study period, the abundance and density of P. glenii increased significantly, coinciding with a marked decline in native fish species. These findings highlight the adaptability of this invasive fish and emphasise the need for targeted management strategies in degraded freshwater ecosystems. Full article

Sarcotaces arcticus (Collett, 1874) is a relatively large, internal parasitic copepod that infects many marine fishes. Although its large size suggests it may have a negative effect on host reproduction by reducing space available in the abdominal cavity (i.e., volumetric effect), such quantitative aspects of host-parasite relationships for S. arcticus have never been documented. We compared the prevalence and the ratio of live to dead parasites among sizes and sexes of two species of rockfish hosts (Sebastes ciliatus, Tilesius, 1813, dark rockfish; and Sebastes variabilis, Pallas, 1814, dusky rockfish) and quantified the reduction of internal space available in infected hosts. Samples were collected in southeast Alaskan waters where the two host rockfish species coexist in sympatry. Both total prevalence and prevalence of live S. arcticus were significantly higher in S. variabilis compared to S. ciliatus, because of higher prevalence in female S. variabilis. The relationship between body cavity volume, volume available for reproduction, and total length was isometric for both host species combined. An average live S. arcticus with a volume of 8.1 milliliters occupied about 45% in smaller hosts and about 5% in larger hosts of the volume available for reproductive organs. The high prevalence and large size of this parasite could significantly reduce fecundity and fitness of rockfish hosts through reductions in internal volume available for reproduction. Full article

Bahaba taipingensis (Chinese bahaba) is a critically endangered fish endemic to China’s coastal waters, valued for both ecological and economic reasons and known as the “panda of the sea”. Captive breeding and stock enhancement are key conservation strategies, yet the genetic composition of released individuals directly affects program outcomes. This study combined mitochondrial and whole-genome resequencing to compare F₁-generation fish with wild populations. At the mitochondrial level, 60 SNPs were detected in F₁ individuals and 72 in wild populations, with haplotype analyses revealing retention of most common maternal lineages but reduced diversity. Nuclear genome analysis showed comparable genetic diversity between groups. Nucleotide diversity (π) was 0.000423 in F₁ fish and 0.000401 in the wild population. However, the F₁ cohort exhibited a higher inbreeding coefficient (F_IS = −0.030) than the wild group (F_IS = −0.118), suggesting early allele frequency shifts, thereby suggesting early genotype frequency shifts. Runs of homozygosity (ROH) analysis showed that the total number and length of ROH regions in the F₁ cohort (686, 283,089.25 kb) were significantly greater than those in the wild population (171, 52,607.30 kb). Genome-wide F_ST between groups was 0.035, and PCA indicated genetic homogenization in F₁ fish. N_e analysis showed that the wild population declined rapidly over generations and stabilized at a low level, indicating genetic diversity loss under environmental stress and highlighting the role of artificial breeding. These findings highlight the need for improved broodstock management and long-term genetic monitoring. Full article