Fishes, Volume 8, Issue 10 (October 2023) – 58 articles

Cryptobenthic fishes make up more than half of coral reef fish fauna and contribute greatly to coral reef trophodynamics and diversity. Because of their small size, they are easily overlooked and understudied. Some of them use corals as their habitat, but this association is not well understood. In the Caribbean, two common cryptobenthic gobies, Elacatinus evelynae and Coryphopterus lipernes, are usually observed residing on corals. In order to compare their habitat use, we investigated their distributions on a range of scleractinian host-coral species at three different depths (5, 10, and 15 m) at Curaçao, southern Caribbean. The numbers of both species were relatively low at 5 m. Furthermore, we investigated the relationship between fish size and depth and found that adult E. evelynae individuals were most common at 5 m depth and juveniles at 15 m depth. Novel host corals were found for both fish species. Taking host size into account, the gobies were most abundant on large coral colonies of two host species: E. evelynae on both Colpophyllia natans and Montastraea cavernosa, and C. lipernes only on C. natans. In summary, depth, host species, and host-colony size were found to be environmental factors that may determine the occurrence of both fish species. Full article

Understanding the spatial distribution of fishing activity and suitable fishing areas is important for improving sustainable fisheries management and protecting vulnerable fish stocks. To identify climate-related habitat changes and variations in the distribution of fishing activity for squid-jigging vessels in the Northwest Pacific Ocean, two types (weighted arithmetic mean method, weighted-AMM; weighted geometric mean method, weighted-GMM) of habitat suitability index (HSI) models were developed in this study with marine environmental data at different depths. The boosted regression tree (BRT) model was adopted to access the monthly important environmental variables and the relative influence of the corresponding variables. The results showed that the weighted-AMM has better prediction performance than the weighted-GMM. The suitable fishing areas showed significant seasonal changes in both spatial location and coverage area. The hotspot map showed that the suitable fishing area for squid-jigging vessels was located in the scope of 42${}^{\circ }$ N∼44${}^{\circ }$ N, 155${}^{\circ }$ E∼170${}^{\circ }$ E throughout the year during 2012∼2019, which suggests that high squid-jigging fishing pressure should be given more attention in fishery management. The HSI model also had good prediction performance for the fishery data of Chinese companies, except for June and July. Additionally, fishing efforts could be used as alternative data for fishery research. The study has also suggested that fishery data are restricted by spatial and temporal distribution and fishing experience, which probably biases the results of the research. Full article

Deep-sea cage aquaculture (DSCA) is an important way to expand new space for marine aquaculture, promote the transformation and upgrade of the fishery industry, and optimize the structure of marine aquaculture. Using the panel data of DSCA in China’s coastal areas from 2013 to 2021, this study constructs the SBM–Malmquist model to measure the DSCA production efficiency and analyzes its total factor productivity. The results show that the overall DSCA production efficiency exhibited an increasing trend in spite of a sharp decline in 2019. The efficiency exhibited regional differences, being the strongest in the Bohai Sea region, followed by in the Yellow Sea, the South China Sea, and the East China Sea regions. The overall total factor productivity remained generally stable, although a large fluctuation occurred between 2019 and 2021. Both pure technological efficiency and scale efficiency promoted the total factor productivity in 2019–2021, while the efficiency of technological changes in societal aspects declined. This study shows that the DSCA production efficiency is significantly influenced by input factors such as labor and capital investment. In addition, natural disasters inhibit the improvement of the production efficiency to some extent. Full article

The complete mitogenomes of Pinctada albina and Pinctada margaritifera were sequenced in this study, with sizes of 23,841 bp and 15,556 bp, respectively. The mitochondrial genome analysis of eight Pterioidea species indicated the existence of gene rearrangements within the superfamily. The ATP8 gene was not detected in the two new mitogenomes, and rrnS was found to be duplicated in P. albina’s mitogenome. The reconstructed phylogeny based on mitogenomes strongly supported the monophyly of Pterioidea and provided robust statistical evidence of the phylogenetic relationships within Pteriomorphia. The analysis of the mitochondrial gene order revealed that of P. margaritifera to be the same as the ancestral order of Pterioidea. The gene orders of the Pterioidea species were mapped to the phylogenetic tree, and the gene rearrangement events were inferred. These results provide important insights that will support future research, such as studies extending the evolutionary patterns of the gene order from P. margaritifera to other species and determining the evolutionary status of Pterioidea within the infraclass Pteriomorphia. Full article

Fishing contributes significantly to food security and offers employment and income to many coastal communities worldwide. On the other hand, it has been recognized as a dangerous and demanding activity that involves high economic risk and uncertainty as well as outdoor work and interactions with nature, which makes fishing more of a way of life rather than just a way to make a living. Non-monetary attributes of fishing have been reported to affect fishers’ decision-making and management and can explain the resilience and sustainability of the sector, even in difficult economic circumstances that hinder profitability. This study uses multivariate statistical analysis to identify profiles of Greek fishers according to their motives and objectives and to link them to the main demographic and socioeconomic characteristics. Overall, five fisher profiles are identified, including “profit maximizers”, “business-oriented” and “subsistence” fishers. Our analysis indicates that all fishers value the non-monetary attributes of the activity higher than monetary values like profit, though large-scale fishers seem to be more business-oriented than small-scale fishers. The identification and understanding of the objective profiles provide useful insights to researchers, advisors and policymakers regarding fishers’ decision-making and can ultimately lead to more efficient policy design and fisheries management. Full article

Aquaculture practices expose fish to several factors that may generate stress, modifying the balance between the production of reactive oxygen species (ROS) and the activity of antioxidant defenses that induce cell damage. Alpha-tocopherol (VE) improves the antioxidant capacity against ROS production in fish. A 50-day trial with longfin yellowtail (Seriola rivoliana) juveniles was conducted to compare the dietary supplementation of 500 mg/kg of VE against a control diet without VE supplementation on growth, lymphoid tissue enzymatic activity, immune-system-related gene expression, and the histology of the liver and spleen. Growth, weight gain, specific growth rate, feed conversion rate, and survival did not show significant differences (p > 0.05) among treatments. Fish fed with an α-tocopherol-enriched diet showed a higher enzymatic activity of superoxide dismutase in the liver (p < 0.05) and a lower percentage of melanomacrophage coverage area in the lymphoid organs (p < 0.05). Overexpression was observed of MyD88 and il-10 in the spleen, and il-1b in the liver in fish fed 500 mg/kg of VE, as well as overexpression of Toll-like 3 in the head kidney, spleen, and liver in fish fed the control diet. Dietary supplementation with VE reduces the effects of oxidative stress and improves lymphoid tissue defense and immune-related gene expression in S. rivoliana. Full article

Katsuwonus pelamis, or skipjack, is a vital resource in purse seine fishing across the Central and Western Pacific. Identifying skipjack distribution hotspots and coldspots is crucial for effective resource management, but the dynamic nature of fish behavior means these spots are not constant. We used Chinese fishing logbook data from 2010 to 2019 to analyze skipjack resource hotspots and coldspots in a space-time cube. The study revealed 13 spatiotemporal patterns in skipjack Catch per Unit Effort (CPUE). Hotspots (36.53%) were concentrated in the central area, predominantly showing oscillating hotspots (21.25%). The significant effect of the eastern oscillating hotspot continues to be enhanced and extends to the east. Coldspots constituted 63.47% of the distribution, mainly represented by intensifying coldspots (25.07%). The no-pattern-detected type (10.53%) is distributed between coldspots and hotspots. The fishing grounds exhibited longitudinal oscillations of 3°–6° and latitudinal oscillations of 1°–2°. The spatial autocorrelation of cold and hot spot distribution was strong, and the spatiotemporal dynamic changes in skipjack resources were closely related to the El Niño-Southern Oscillation (ENSO) phenomenon. Notably, during 2011–2016, hotspots exhibited an eastward expansion trend, which continued from 2017–2019 due to the influence of fishery management measures, such as the Vessel Day Scheme (VDS) system. Full article

Molting is an essential operation in the life of every lobster, and observing this process will help us to assist lobsters in their recovery. However, traditional observation consumes a significant amount of time and labor. This study aims to develop an autonomous AI-based robot monitoring system to detect molt. In this study, we used an optimized Yolov5s algorithm and DeepLabCut tool to analyze and detect all six molting phases such as S1 (normal), S2 (stress), S3–S5 (molt), and S6 (exoskeleton). We constructed the proposed optimized Yolov5s algorithm to analyze the frequency of posture change between S1 (normal) and S2 (stress). During this stage, if the lobster stays stressed for 80% of the past 6 h, the system will assign the keypoint from the DeepLabCut tool to the lobster hip. The process primarily concentrates on the S3–S5 stage to identify the variation in the hatching spot. At the end of this process, the system will re-import the optimized Yolov5s to detect the presence of an independent shell, S6, inside the tank. The optimized Yolov5s embedded a Convolutional Block Attention Module into the backbone network to improve the feature extraction capability of the model, which has been evaluated by evaluation metrics, comparison studies, and IoU comparisons between Yolo’s to understand the network’s performance. Additionally, we conducted experiments to measure the accuracy of the DeepLabCut Tool’s detections. Full article

The warming and acidification of surface waters as predicted by the IPCC leads aquatic species to face major multifaceted changes in their environment. Although teleosts have efficient regulatory systems to cope with these changes, such changes clearly have the potential to impact their physiological functions. Hence, it is crucial to estimate the ability of teleost fishes to cope with multi-stresses to predict how they will deal with future environments. In this context, we investigated the joint effect of warming and acidification on three-spined stickleback (Gasterosteus aculeatus) from the juvenile stage to adulthood, focusing on parameters linked to growth, sexual maturation, and reproduction. Juvenile sticklebacks were split in 2 climate scenarios: a “Current” scenario corresponding to the current seasonal physico-chemical parameters of the water of the “Rade de Brest” in France, and a “RCP8.5” scenario with a warming of 3 °C and an acidification of 0.4 pH units. After 7 months, fish in the RCP8.5 scenario reached the same size and mass as those in the Current scenario, but they needed greater amounts of food to reach satiety. Furthermore, the mortality rate over the experiment was higher in the RCP8.5 scenario. Muscle lipid content, an indicator of energy reserves, was lower in females in the RCP8.5 scenario, suggesting an increased need for energy to maintain homeostasis and other physiological functions or a divergence in energy allocation strategy. Moreover, females exhibited lower sexual maturation and egg quality under the RCP8.5 scenario, which could have contributed to the lower fertilisation rate observed. Males were more resilient to the RCP8.5 scenario, exhibiting only a trend for lower kidney somatic index scores. Altogether, these results suggest a delay and/or an inhibition of gametogenesis and maturation in fish in warmed and acidified waters. The analysis of blood sex steroid concentrations, brain gene expression profiles, and physiological indexes did not allow us to discriminate between a delay and an inhibition of maturation in the RCP8.5 scenario. Overall, these findings clearly indicate that there is a long-term global impact of combined acidification and warming on the mortality and reproductive performance of three-spined stickleback. Full article

Two specimens of large blackish chimaeras of the genus Hydrolagus were caught, one off Reunion Island and the other off Mayotte in the southwestern Indian Ocean. The specimens, an adult male of 710 mm BDL and a female of 870 m BDL, are described, compared to similar species (i.e., having a large size, over 110 cm TL, dark blackish colour, and rather long conical snout), and tentatively identified to the small-eyed rabbitfish Hydrolagus affinis, pending a taxonomic revision of the large blackish chimaeras is completed. Full article

During winter, stream fishes are vulnerable to semi-aquatic predators like mammals and birds and reduce encounters by being active in darkness or under surface ice. Less is known about the behavior of fishes towards instream piscivorous fishes. Here, we examined how surface ice and light affected the anti-predator behavior of juvenile brown trout (Salmo trutta Linnaeus, 1758) in relation to piscivorous burbot (Lota lota Linnaeus, 1758) and northern pike (Esox lucius Linnaeus, 1758) at 4 °C in experimental flumes. Trout had lower foraging and swimming activity and spent more time sheltering when predators were present than when absent. In daylight, trout’s swimming activity was not affected by predators, whereas in darkness trout were less active when predators were present. Trout consumed more drifting prey during the day when ice was present, and they positioned themselves further upstream when under ice cover, regardless of light conditions. Trout stayed closer to conspecifics under ice, but only in the presence of pike. Piscivorous fishes thus constitute an essential part of the predatory landscape of juvenile trout in winter, and thus loss of ice cover caused by climate warming will likely affect trout’s interactions with predators. Full article

The Shortfin mako shark, Isurus oxyrinchus Rafinesque, 1810, is a globally distributed highly migratory pelagic shark species, occurring mostly in temperate and tropical regions, including the Mediterranean Sea where it is by-caught during fishing activities targeting other economically important fish species. The aim of this study is to investigate the genetic connectivity of the Shortfin mako from the central Mediterranean Sea to previously studied populations. The mtDNA control region (CR), 977 bp, of 37 I. oxyrinchus specimens collected between 2004 and 2012 from landings in Malta were analysed, and we identified nine haplotypes, including three newly discovered haplotypes that may be unique to the Mediterranean Sea and which represent 16.7% of the studied individuals. These haplotypes, together with variations in haplotype frequencies, led to significant F_ST and ϕST values between the Mediterranean population and other global populations, with the exception of that from the north Atlantic Ocean. This study provides the first insight of the mtDNA CR diversity of this critically endangered species in the Mediterranean Sea and highlights the importance of conserving this species in the region. Full article

Intrinsic tracers, such as stable isotopes of carbon and nitrogen, are common dietary markers that accumulate in the muscle tissue of consumers and can be used to determine the dietary sources and trophic positions of consumers. The aim of this study was to assess regional variation in the trophic ecology of wahoo (Acanthocybium solandri) using bulk stable isotopes. Muscle biopsies of wahoo were collected from four regions in the western Atlantic Ocean: the eastern Gulf of Mexico, western Gulf of Mexico, Northwest Atlantic Ocean, and Caribbean Sea. Muscle tissue δ¹³C and δ¹⁵N values for wahoo ranged from −15.8‰ to −18.8‰ and from 7.2‰ to 12.8‰, respectively. Wahoo collected in the Caribbean Sea displayed the highest mean δ¹³C value (−16.3‰), and individuals from this region were statistically different from the three other regions sampled. Mean δ¹⁵N values were elevated for wahoo collected in the eastern and western Gulf of Mexico (11.4‰ and 11.1‰, respectively), and the values were over 2‰ higher than samples from the Northwest Atlantic Ocean and Caribbean Sea. Trophic position (TP) was estimated using δ¹⁵N baselines (zooplankton) and δ¹⁵N wahoo values for each region, and mean TP was 0.4 to 0.9 higher in the Caribbean Sea relative to the three other regions, suggesting that wahoo in this region feed on higher-trophic-level prey. The results indicate that δ¹⁵N baselines and the trophic positions of wahoo each vary as a function of their geographic location, which supports the hypothesis that this species feeds opportunistically throughout its range. Full article

In South America, knowledge of major spawning sites is crucial for maintaining migratory fish populations. In this study, we aimed to understand the spatio-temporal distribution of fish eggs in the upper São Francisco River using high sampling frequency and DNA metabarcoding identification. We evaluated the possible effects of the non-molecular identification of eggs and decreased sampling frequency on the determination of spawning sites and major breeding periods. Collections were carried out every three days from November 2019 to February 2020. We found that, if we had assumed that all of the free and non-adhesive sampled eggs belonged to migratory species, as is usual in the literature, this assumption would have been wrong for both the spawning sites and the breeding periods. Moreover, any decrease in the frequency of sampling could dramatically affect the determination of the major spawning rivers, and the spawning events of some of the migratory species may not have been detected. Therefore, without the proper identification and adequate sampling frequency of eggs, important spawning sites may be overlooked, leading to ineffective or inappropriate conservation measures. Full article

Freshwater turtles are among the least studied faunas in the Andaman and Nicobar Islands, India. Here, we report the presence of freshwater turtles (Cuora amboinensis) from Car Nicobar, a small remote island in the Nicobar archipelago comprising the Andaman and Nicobar Islands. Semi-structured interviews were conducted with the people belonging to Nicobarese tribes (n = 233) to gather their local ecological knowledge as supportive information to obtain a better understanding of the status of turtles in Car Nicobar. Most interviewees (90%) opined that freshwater turtles are found to be rare or very rare on the Island. All the respondents (100%) expressed willingness to contribute to future conservation projects. Community-level awareness emerged as a prominent issue for future conservation using the Garrett ranking method. A stream network map was prepared using the digital elevation model to visualize streams and potential habitats of turtles. This report on the freshwater turtles is essential from an ecological perspective since information is scarce on the freshwater turtles in Car Nicobar. This study emphasizes the importance of the engagement of stakeholders in conservation projects and recommends providing adequate attention to the conservation and protection of freshwater turtle diversity in Car Nicobar. Full article

Monitoring and understanding the behavior of fishing vessels are important in facilitating effective management, preventing illegal fishing, informing fishing grounds and evaluating effects of harvests on fishery resources. In recent decades, a large quantity of real-time data of fishing vessels have become available with the development of vessel-tracking systems, making it possible to study the behavior of fishing vessels in high spatial and temporal resolutions. To effectively and efficiently deal with the large amount of data, algorithms from artificial intelligence (AI) are increasingly applied in the study of fishing vessel behavior. In this paper, we first introduce the various data sources for studying fishing vessel behavior and compare their pros and cons. Secondly, we review the AI methods that have been used to monitor and extract the behavior of fishing vessels from big data. Then, studies on the physical, ecological and social mechanisms affecting the behavior of fishing vessels were synthesized. Lastly, we review the applications of fishing vessel behavior in fishery science and management. Full article

In this study, the compound aquaculture model of red tilapia (O. mossambicus albina × O. urolepis hornorum) and water spinach (Ipomoea aquatica) was used to investigate the effect of water spinach rafts on the water quality, antioxidant system, non-specific immune response, and growth performance of red tilapia and the carbon balance of payments. Red tilapia is characterized by its high adaptability to different production environments and food sources, as one of the most productive fish in aquaculture, and is well accepted in the market due to its nutritional and organoleptic characteristics. The experiment lasted for nine weeks and included two systems: the red tilapia-water spinach raft aquaponics (AP) system with 10% cover ratio with water spinach floating beds, and the aquatic monoculture (AM) system with only red tilapia. The total phosphorus (TP), total nitrogen (TN), and nitrate nitrogen (NO⁻₃-N) in the AM were higher than those in AP from the fifth to ninth week. On the second, third, fifth, and sixth weeks, the ammonia nitrogen (NH₄⁺-N), in the AM was higher than those in the AP. From the seventh week, the pH of the AM was significantly lower than the AP, while the nitrite nitrogen (NO⁻₂-N) was significantly higher than the AP. The water quality index of the AP was better than that of the AM, indicating that water spinach can remove the nutrients from aquaculture water bodies. The average daily gain and specific growth rate (SGR) of fish in AP were higher than those in the AM. The acid phosphatase (ACP), alkaline phosphatase (AKP), and catalase (CAT) activities in the hepatopancreas of red tilapia in the AP were also significantly higher than those in the AM, while the malondialdehyde (MDA) in the AP was lower than the AM. The serum ACP and CAT of red tilapia in the AP were also higher than those in the AM, while the MDA of fish in the AP was lower than the AM. The results showed that both the experimental group and the control group were carbon sources and released greenhouse gases into the atmosphere, but the total carbon emissions of the red tilapia and the water spinach symbiotic system in the experimental group was significantly lower than that of the control group (p < 0.05). These results demonstrated that the application of water spinach rafts in aquaponics can not only improve the water quality, but also improve the growth performance, antioxidant system and non-specific immune responses of red tilapia, while promoting the utilization of organic matter in the aquaculture system, improving the ecological benefits in terms of the carbon income and expenditure. Full article

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

Alcichthys elongatus is the only species in the genus, and this work is the first to provide a comprehensive mitogenome analysis of this species. The A. elongatus mitogenome was 16,712 bp long, with biased A + T content (52.33%), and featured thirteen protein-coding genes (PCGs), twenty-two tRNAs, two rRNAs, and the control region (D-loop). The H strand encoded twenty-eight genes (twelve PCGs, fourteen tRNA, and two rRNA) and the control region, whereas the L strand encoded the remaining nine genes (ND6 and eight tRNA). Except for COXI, which started with GTG, all PCG sequences started with ATG and ended with TAA (ND4L, ND5, COXI, ATP8) or TAG (ND1, ND6) termination codons, with some (ND2, ND3, ND4, COXII, COXIII, ATP6, Cytb) having an incomplete termination codon. Except for tRNA-serine-1 (trnS), the majority of the tRNAs exhibited characteristic cloverleaf secondary structures. Based on 13 PCGs, phylogenetic analysis placed A. elongatus in the same clade as Icelus spatula. This genomic data will be useful for species identification, phylogenetic analysis, and population genetics. Full article

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 study explored the ecological niche and interspecific relationships among the main fish species in the coastal waters of Hainan Island based on data from fishery stock surveys conducted in the spring and autumn of 2022. The methods of chi-square test, percentage of co-occurrence (PC), association coefficient (AC), cluster analysis, and redundancy analysis were used to analyze the interspecific associations and influence of environmental factors on the ecological niches of fish communities. According to the cluster analysis of niche breadth, 20 main fishes could be divided into broad, medium, and narrow niche species. There were four and eight broad niche species in spring and autumn, respectively. The ranges of niche overlap values were 0.001–0.91 in spring and 0–0.87 in autumn, indicating that the species differed and were similar in their ability to utilize resources, survive in habitats, and prey. According to the variance ratio and statistic value W, the main fishes in spring showed a significant positive association, whereas those in autumn showed a positive association, but not at a significant level, indicating that the main fishes in spring were more closely associated with each other. There were 56 species pairs in the 2 seasons that were significantly associated (χ² ≥ 3.841). AC and PC tests revealed that the interspecific association was strong and tended to be positive. According to the redundancy analysis, environmental factors such as surface temperature, water depth, and pH significantly affected the main fishes in spring, while environmental factors such as dissolved oxygen, bottom temperature, surface salinity, and pH significantly affected those in autumn. Full article

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

The present study evaluated different levels of the essential oil of Nectandra grandiflora (EONG) in the diet of juvenile Colossoma macropomum. The juveniles (0.75 ± 0.05 g) were fed four experimental diets with differing levels of EONG (0, 0.5, 0.75, and 1.50 mL/kg). After 20 days, the weight, daily weight gain, specific growth rate, and daily feed consumption per fish were highest for the fish fed 0.5 mL EONG/kg, while after 30 days, only the weight and daily feed consumption per fish for that diet remained highest. The viscerosomatic index was highest for the fish fed 0.5 mL EONG/kg while the hepatosomatic index was higher for the groups that received dietary EONG for 30 days. The juveniles fed 1.5 mL EONG/kg showed a proliferative response of the mucous cells in the gills, but the proliferation of these lysozyme- and immunoglobulin-secreting mucosal cells was higher for the skin of the fish of all EONG levels, compared to that of the control fish. The fish fed 0.5 mL EONG/kg had the greatest height and width of intestinal villi. The two highest levels of dietary EONG supplementation (0.75 and 1.50 mL/kg) reduced the hepatocyte dimensions but did not modify the centrolobular vein area. Dietary supplementation with 0.5 mL EONG/kg improved the growth, gut health, and immune response of juvenile C. macropomum. Full article

Rockfishes (Sebastes spp.) are a long-lived, understudied, multi-species fish assemblage in inland Washington (USA) waters. Driven by large-scale fishery removals in the 1970s, their numbers declined and have yet to recover, perhaps due to slow maturation and rare recruitment success. Since then, rockfish fishing restrictions have increased within Puget Sound, culminating in a 2010 total ban. Here, we analyze rockfish community trends (abundance and Shannon Diversity) within Puget Sound from 2009 to 2023. Our dataset includes 157 recorded dive transects from nine rocky or artificial reef habitats at depths 5–24 m throughout four Puget Sound basins: Admiralty Inlet (2 sites), Central Puget Sound (4 sites), Hood Canal (2 sites), and South Puget Sound (1 site). Significant differences in community species composition between basins were observed; we noted more Black (S. melanops), Yellowtail (S. flavidus), and Puget Sound (S. emphaeus) rockfish and fewer Brown rockfish (S. auriculatus) at sites in Admiralty Inlet vs. Central Puget Sound. Adult rockfish counts and Shannon Diversity varied seasonally, with higher rockfish counts and diversity indices in summer/autumn vs. winter/spring. Notably, we observed that total adult rockfish count per survey tended downward over time, driven partly by significant downward trends in Hood Canal Copper rockfish (S. caurinus) counts. We recommend continued monitoring and additional investigation into what factors besides fishing may be driving the trends reported here. Full article

This study aimed to investigate the effect of reduced expression of the luxR gene on the virulence of Pseudomonas plecoglossicida and the immune response of Epinephelus coioides. To achieve this, RNA interference (RNAi) was used to silence the luxR gene, and the pathogenicity of wild-type and luxR-RNAi strains of P. plecoglossicida, as well as the immune response of Epinephelus coioides to the infection of these two strains, were compared. The mutant strain with the highest silencing efficiency of 70.1% was selected for subsequent analysis. Silencing the luxR gene in the mutant strain resulted in a significant 30% reduction in mortality rates in artificially infected Epinephelus coioides compared to the wild-type strain. Transcriptome analysis revealed that the host transcriptome, particularly in the spleens of infected Epinephelus coioides, was markedly altered by the silencing of the luxR gene in the mutant strain. Tilapia infected with the luxR-RNAi strain exhibited altered immune defenses, with changes in gene expression primarily in the NOD-like receptor (NLR) signaling pathway. These results suggest that the luxR gene plays a crucial role in the host’s resistance to pathogen invasion, and reducing its expression could decrease quorum sensing (QS) signals while increasing the expression of the IL-1β gene in the host’s NLR pathway. This effect may lead to a pro-inflammatory response that enhances the immune response to infection. Further investigation of these mechanisms may lead to innovative approaches to treating bacterial infections. Full article

Pheromones play a vital role in regulating fish behavior, including reproduction, aggregation, hazard recognition and food location. To gain a better understanding of chemical communication in fish produced by density changes, this study analyzed the metabolites released by turbot (Scophthalmus maximus) under different stocking densities. The experiment was conducted at low (LD: 3.01 kg/m²), medium (MD: 6.62 kg/m²) and high (HD: 10.84 kg/m²) densities for 15 days. High-throughput non-targeted metabolomics (LC-MS/MS) was used to identify variations in metabolites released into the aquatic environment by turbot at different densities. Results showed that 29 and 47 metabolites were significantly upregulated in the MD and HD groups, respectively, compared with the LD group. Among them, hexadecanedioic acid, xanthine, phenethylamine, proline and styrene were significantly upregulated in the MD vs. LD, HD vs. MD and HD vs. LD. The VIP diagram of OPLS-DA alignment showed that phenethylamine was the most important metabolite shared by MD vs. LD, HD vs. MD and HD vs. LD. Key gene changes in the GH/IGF-1 signaling pathway, HPI axis of turbot were studied using qRT-PCR for density treatment. The results demonstrated that the expression of GH, GHR and IGF-1 was significantly lower, while the expression of CRH and ACTH was higher in the HD group. Additionally, plasma levels of cortisol, glucose, triglycerides and T₃ were also highest in the HD group compared with the LD and MD groups. Phenylethylamine concentration was positively correlated with the HPI axis and negatively correlated with the GH/IGF-1 signaling pathway. To investigate the impact of phenethylamine accumulation on turbot, an acute treatment experiment with phenethylamine was set up. Its concentration in the aquatic environment was set at 0 (CON), 10⁻⁷ (LP) and 10⁻⁵ (HP) mol/L via exogenous addition, and turbot were exposed to these environments for 2 days. There was a high degree of concordance between the GH/IGF-1 signaling pathway (GH, GHR, IGF-1), HPI axis (CRH, ACTH) and plasma physiological changes (cortisol, glucose, triglycerides, T₃) in the phenethylamine-treated group and the density-treated group. Therefore, accumulation of phenethylamine with increasing stocking density may be a potential cause of density stress. Phenylethylamine has a dose-dependent and trace effect as a pheromone. Full article

Fish play a major role in the human nutritional system, and farmers need to know the accurate prediction of fish weight in order to optimize the production process and reduce costs. However, existing prediction methods are not efficient. The formulas for calculating fish weight are generally designed for a single species of fish or for species of a similar shape. In this paper, a new hybrid method called SFI-XGBoost is proposed. It combines the VIF (variance inflation factor), PCC (Pearson’s correlation coefficient), and XGBoost methods, and it covers different fish species. By applying GridSearchCV validation, normalization, augmentation, and encoding techniques, the obtained results show that SFI-XGBoost is more efficient than simple XGBoost. The model generated by our approach is more generalized, achieving accurate results with a wide variety of species. Using the r2_score evaluation metric, SFI-XGBoost achieves an accuracy rate of 99.94%. Full article

Otoliths grow throughout a fish’s life and are important for identifying fish stocks and fish age. This study aims to differentiate different stocks of Schizothorax grahami (Regan, 1904) in the Chishui River, an upper reach of the Yangtze River, by otolith morphology. The otolith morphology of S. grahami from three different river sections was analyzed using the Shape Index, Fourier coefficients, and wavelet coefficients. The composite discrimination success rate of the Shape Index was 59.7%, and it was difficult to distinguish in the scatter plots. In contrast, canonical principal coordinate scatter plots clearly showed three distinguished stocks. The above results indicate that otolith morphology can discriminate between stocks in plateau endemic fish, and several S. grahami stocks may be separately managed in the Chishui River. Full article

In order to study the community of fishery resources, five sampling sections were set up in the lower Yellow River from 2019 to 2022 to investigate the diversity of fishery resources. A total of 54 fish species were identified in the survey, belonging to 9 orders, 19 families, and 48 genera. The number of species reached its highest level since the Integrated Water Regulation of the Lower Yellow River in 1999. The original rare and endangered fish species in the lower reaches of the Yellow River, such as Coilia nasus, Rhinogobio nasutus, and Pseudobagrus ussuriensis, have reappeared in the lower reaches. The population and abundance of main economic fish and common small-sized fish in the lower reaches of the Yellow River have increased. These signs all indicate that, and the fishery resources are recovering slowly in the lower Yellow River. By comparing the fish resources of various investigation sections, it was found that there are differences in fish diversity: the closer to the estuarine waters, the higher the variety of fish in the Yellow River at the upper level of the taxonomic category. However, that section of the lower Yellow River where species evenness, species diversity, and community structure of fishery resources were most stable was the confluence of Dongping Lake into the Yellow River, which has the most significant number of fish species, the smallest Λ⁺ value, and the most extensive G-F index. The above results indicate that Dongping Lake, as the only lake connected to the lower reaches of the Yellow River, plays an essential role in replenishing fish resources in the lower reaches of the Yellow River. Full article

In recent years, with the development of pelagic fishing, the working environment and monitoring of crew (squid jigger) members have become increasingly important. However, traditional methods of pelagic human observers suffer from high costs, low coverage, poor timeliness, and susceptibility to subjective factors. In contrast, the Electronic Monitoring System (EMS) has advantages such as continuous operation under various weather conditions; more objective, transparent, and efficient data; and less interference with fishing operations. This paper shows how the 3DCNN model, LSTM+ResNet model, and TimeSformer model are applied to video-classification tasks, and for the first time, they are applied to an EMS. In addition, this paper tests and compares the application effects of the three models on video classification, and discusses the advantages and challenges of using them for video recognition. Through experiments, we obtained the accuracy and relevant indicators of video recognition using different models. The research results show that when NUM_FRAMES is set to 8, the LSTM+ResNet-50 model has the best performance, with an accuracy of 88.47%, an $F1$ score of 0.8881, and an $m_{ap}$ score of 0.8133. Analyzing the EMS for pelagic fishing can improve China’s performance level and management efficiency in pelagic fishing, and promote the development of the fishery knowledge service system and smart fishery engineering. Full article