Fishes

The aim of this study was to evaluate the utilization of fairy shrimp (Branchinella thailandensis) meal in the diets of flowerhorn cichlids, on their growth, skin coloration, carotenoid content, antioxidant activity, and innate immunity. The fish were fed diets incorporated with fairy shrimp meal at 0% (control; FS0), 10% (FS10), 20% (FS20), and 30% (FS30) for 60 days. The results showed that growth performance and chemical composition were not significantly different among treatments (p > 0.05), whereas fish fed the 30% fairy shrimp meal (FS30) diet represented significantly enhanced skin coloration, particularly in terms of redness (a*) and dominant wavelength (H°ab). The highest level of antioxidant enzymes and non-specific immune enzymes such as SOD and lysozyme were observed in the fish fed the FS30 diet. Meanwhile, increasing fairy shrimp meal significantly reduced the liver function markers (ALT and AST), and decreased lipid peroxidation. These findings suggest that fairy shrimp meal serves as a valuable dietary ingredient for enhancing skin pigmentation, boosting antioxidant defense, and stimulating immune responses in flowerhorn cichlids. Moreover, the economic evaluation of using fairy shrimp meal as an ingredient for ornamental fish demonstrates promising investment potential, supporting its application in commercial aquaculture.

The accumulation of cadmium (Cd) and microplastics (MPs) can have major deleterious effects on the health of marine ecosystems and organisms, including the pearl oyster Pinctada fucata martensii. Here, we characterized the effects of Cd and MPs on key biochemical parameters of P. f. martensii via an experiment with various treatments. Pearl oysters were exposed to either only Cd (5 or 50 μg/L), only MPs (5 mg/L), or both Cd and MPs for 2 d, and this was followed by a 5-day recovery period. Measurements of the activities of lipase, amylase, protease, T-ATPase, catalase, glutathione peroxidase, acid phosphatase, and alkaline phosphatase enzymes, as well as the malondialdehyde content in the hepatopancreas, were made at various time points during the experiment. Metabolomics analysis of the gills was also performed. Significant interactions between time and treatment on lipase, protease, and catalase activities were observed. However, no significant effect of time–treatment interactions on amylase and T-ATPase activities was observed. Enzyme activities varied among groups both during the exposure period (6 to 48 h) and the recovery period. The malondialdehyde content was also increased throughout the experiment. Pathway analysis indicated that the purine metabolism, glycerophospholipid metabolism, nucleotide metabolism, arachidonic acid metabolism, neuroactive ligand–receptor interaction, and linoleic acid metabolism pathways were the most commonly affected under different treatments. The findings of our study revealed the differential effects of exposure time and treatment on enzyme activities and metabolites and their respective pathways. Our findings enhance our understanding of the biochemical responses of the pearl oyster P. f. martensii to environmental stressors, particularly Cd and MPs.

Imidacloprid (IMI), a widely used neonicotinoid insecticide, has raised environmental concerns due to its potential impact on non-target aquatic organisms. This study investigates the effects of IMI exposure on the intestinal immune function of red swamp crayfish (Procambarus clarkii, P. clarkii), focusing on oxidative stress, inflammatory response, and autophagy. The P. clarkii was exposed to different doses of IMI (0, 10.93, 21.86, 43.73, 87.45 μg/L) for 96 h. Our findings reveal that IMI exposure leads to a survival rate of less than 70% when the concentration was 87.45 μg/L at 96 h. Hemolymph LZM and AKP contents were significantly decreased at the medium and high concentrations, and the expressions of hsp70 and nf-κb genes were significantly up-regulated. The expression of the lysozyme gene was significantly down-regulated. Additionally, the activities of SOD, CAT, and GPX were significantly decreased, the contents of MDA were significantly increased, and the gene expressions of CuZnsod, mMnsod, cat, and gpx in the gut were significantly down-regulated after exposure to medium-high IMI. The expression of autophagy-related genes showed that the expressions of beclin1, atg5, atg13, and lc3c genes in the medium- and high-concentration groups were significantly up-regulated. In summary, this study elucidates that medium-high levels of IMI exposure impair intestinal immune function in P. clarkii through mechanisms involving oxidative stress, inflammatory response, and autophagy.

Popular foods such as sushi and sashimi depend on the quality of raw fish meat to maintain consumer satisfaction. Recently, dietary insect meal and insect-derived substances have been extensively studied for application in aquaculture as a protein alternative or immunostimulant. However, the impact of insect functional substances on the fish meat quality of teleosts remains unclear. Here, we investigated the influence of dietary inclusion of silkrose-BM, a novel bioactive polysaccharide derived from the silkworm, Bombyx mori, on the meat quality of yellowtail (Seriola quinqueradiata). This study was conducted by comparing two groups given different feeds, commercial EP and feeds containing Silkrose-BM (0.1%), after a culture period of six months in separate floating-net cages. The yellowtail were specifically cut into loins and several meat quality parameters were observed, including proximate, meat color changes, total collagen, drip loss, muscle histology, and gene expression (qRT-PCR). The results of the color-change analysis showed that discoloration of red muscle in the EP feed group occurred faster than in the silkrose-BM group, indicating an antioxidant property of silkrose-BM. Dietary silkrose-BM also significantly reduced drip loss and increased the total collagen content of yellowtail meat. Furthermore, qRT-PCR analysis showed that genes related to lipid and protein degradation were downregulated in the muscles of fish fed on silkrose-BM. In contrast, proximate analysis indicated no significant change in the nutritional composition of the meat between the groups. Taken together, our results suggest that dietary silkrose-BM could improve fish meat quality by minimizing protein denaturation and inhibiting lipid oxidation during fish meat storage.

The golden pompano ranks at the top of production in current China’s marine fish aquaculture; however, there has been long-standing controversy regarding its valid scientific name. Multiple latin names were used simultaneously to refer to golden pompano, such as Trachinotus ovatus, T. blochii, T. mookalee and T. anak. Moreover, two distinct morphological species are regarded as deserving the scientific name T. ovatus. In this study, we employed DNA barcoding to determine which particular species the “golden pompano” represents and to explore the potential synonyms and cryptic species within T. ovatus and its closely related species. We analyzed the DNA barcodes of golden pompano samples from various aquaculture farms in China’s main production regions, as well as most species within the genus Trachinotus. The phylogenetic analyses revealed that all T. ovatus sequences clustered into two divergent clades with a large genetic distance, and the two clades were geographically separated, being from the Indo-west Pacific and the East Atlantic regions, respectively. Based on the type locality information and historical distribution records, we support the validity of the naming of Trachinotus ovatus from the Indo-west Pacific, and the so-called Trachinotus ovatus from the East Atlantic may represent a cryptic species. All the golden pompano samples were clustered into the Indo-west Pacific T. ovatus clade, with a considerably small intragroup genetic distance, which suggests that the golden pompano in China should be identified as the species Trachinotus ovatus. The golden pompano, T. blochii and T. mookalee were completely separated into distinct monophyletic clades in the phylogenetic trees, which indicated that they are different species. The T. anak clustered with the monophyletic clade of Indo-west Pacific T. ovatus and the genetic distance between them was at the intraspecific difference level. This implied that the T. anak might be the junior synonym of T. ovatus. The species delimitations based on the ABGD and bPTP methods are in agreement with the findings from phylogenetic analyses. The above results help to form a consistent viewpoint regarding the naming of the golden pompano and provide new understandings for the taxonomy of the genus Trachinotus.

The impact of dietary lipid sources on nutrient metabolism and reproductive development is a critical focus in aquaculture broodstock nutrition. Previous studies have demonstrated that fish oil supplementation modulates the expression of genes involved in steroid hormone synthesis, glucose, and lipid metabolism promoting ovarian development in female Scatophagus argus (spotted scat). However, the effects of fish oil on hepatic function at the protein level remain poorly characterized. In this study, female S. argus were fed diets containing 8% fish oil (FO, experimental group) or 8% soybean oil (SO, control group) for 60 days. Comparative proteomic analysis of liver tissue identified significant differential protein expression between groups. The FO group exhibited upregulation of lipid metabolism-related proteins, including COMM domain-containing protein 1 (Commd1), tetraspanin 8 (Tspan8), myoglobin (Mb), transmembrane protein 41B (Tmem41b), stromal cell-derived factor 2-like protein 1 (Sdf2l1), and peroxisomal biogenesis factor 5 (Pex5). Additionally, glucose metabolism-associated proteins, such as Sdf2l1 and non-POU domain-containing octamer-binding protein (Nono), were elevated in the FO group. Moreover, proteins linked to inflammation and antioxidant responses, including G protein-coupled receptor 108 (Gpr108), protein tyrosine phosphatase non-receptor type 2 (Ptpn2), Pex5, p120 catenin (Ctnnd1), tripartite motif-containing protein 16 (Trim16), and aquaporin 11 (Aqp11), were elevated in the FO group, while proteins involved in oxidative stress, such as reactive oxygen species modulator 1 (Romo1), cathepsin A (Ctsa), and Cullin 4A (Cul4a), were downregulated. These proteomic findings align with prior transcriptomic data, indicating that dietary fish oil enhances hepatic lipid metabolism, mitigates oxidative stress, and strengthens antioxidant capacity. Furthermore, these hepatic adaptations may synergistically support ovarian maturation in S. argus. This study provides novel proteomic-level evidence supporting the role of fish oil in modulating hepatic lipid and energy metabolism, thereby elucidating the role of fish oil in optimizing hepatic energy metabolism and redox homeostasis to influence reproductive processes, advancing our understanding of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) in teleost liver physiology.

Tub gurnard, Chelidonichthys lucerna, is a common and widely distributed species throughout the Sea of Marmara (SoM). The knowledge on the spatial distribution of tub gurnards in the SoM in association with environmental factors is limited. The relationship between tub gurnard abundance and environmental variables (depth, temperature, dissolved oxygen, pH, and spatial variability) in the eastern Sea of Marmara (ESoM) was analyzed by means of the generalized additive model (GAM) in the present study. Additionally, the size distribution of tub gurnards was examined in relation to depth and season. Data were collected over an 11-year sampling period (2014–2024) within the scope of scientific demersal trawl surveys in the ESoM. The GAM results revealed that while all the analyzed variables influenced the spatial distribution patterns of tub gurnards, temperature and depth were the most significant contributors in the ESoM. The abundance of tub gurnard exhibited a strongly nonlinear relationship with the explanatory covariates. Regarding the depth distribution patterns of tub gurnards in association with fish size, statistical tests showed significant differences between the size frequency distributions in the two depth ranges, of which the mean total lengths were 24.1 ± 6.90 and 23.5 ± 4.27 cm for depths >80 and <80 m, respectively. A preferred depth was obviously expressed, with tub gurnards moving into deeper water as they grew larger. The mean sizes (range) were 23.56 ± 6.92 cm (13.1–69.6 cm), 24.8 ± 5.35 cm (17.1–58.5 cm), 24.9 ± 8.14 cm (13.1–56.5 cm), and 23.0 ± 5.22 cm (14.2–46 cm) for winter, spring, summer, and autumn, respectively. Therefore, the observed distribution patterns highlight the influence of environmental factors on the abundance of tub gurnard species.

The largescale blackfish, Girella punctata Gray, 1835, is important in the fishing industry and recreational fishing, and it is also cultured in East Asia. Cymothoidae (Crustacea: Isopoda) is a group of parasites that infest fish in marine, brackish, and freshwater environments. In this study, we report, for the first time, Ceratothoa arimae (Nunomura, 2001) (Cymothoidae) from the buccal cavity of G. punctata in the Seto Inland Sea, Japan. Ceratothoa arimae showed a prevalence of 29.4–66.7% in G. punctata. The morphology of the mancae of this species was also described in comparison with that of the adult female (ovigerous), transitional stage, and adult male. The manca of Ceratothoa arimae has more chromatophores than those of other Ceratothoa species from Japan, and is a candidate for a future taxonomic trait. This species may have a negative impact on cultured G. punctata, which would be important to determine in future studies. Currently, it is difficult to identify cymothoid mancae species based on their morphology, but the information provided in this study could be useful when combined with other methods developed in the future, such as molecular analysis.

Recirculating aquaculture systems (RAS) have promising applications in aquaculture. Feed is recognized as a major source of input to the RAS, and feeding frequency will not only impact the performance of turbot, but will also impact the quality of the cultured water. In order to rationally manage feeding and reduce aquaculture pollution, this study investigated the effects of feeding frequency on the performance of turbot (Scophthalmus maximus), nitrogen removal (ammonia and nitrite) characteristics and microbial communities in biofilters. The experiment was designed with three treatment groups, which were categorized into feeding once/day (FF1), feeding twice/day (FF2) and feeding three times/day (FF3) for 30 days. The results indicated that weight gain rate (WGR) and specific growth rate (SGR) significantly increased (p < 0.05) in the FF2 group and FF3 group compared with the FF1 group. The feed conversion ratio (FCR) was significantly lower (p < 0.05) in the FF2 group and FF3 group than in the FF1 group. There was no significant change in condition factor (CF). Ammonia and nitrite concentration decreased and water quality fluctuated less as the feeding frequency increased. FF2 showed the highest ammonia and nitrite removal rates. Feeding frequency did not significantly affect biofilter alpha diversity, but significantly altered beta diversity. PICRUSt functional prediction analysis revealed that the relative abundance of functional genes for nitrogen metabolism (amoA, amoB, amoC, hao, nxrA and nxrB) was highest in FF2. Therefore, feeding frequency of twice/day not only benefits the performance of turbot but also stabilizes the water environment and improves the removal of ammonia nitrogen and nitrite in RAS. These results provide theoretical and practical basis for further water improvement by seawater RAS.

An eight-week feeding trial was conducted to evaluate the effects of dietary supplementation with glycerol monolaurate (GML) on Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated containing 100 g fish meal, while four additional GML-supplemented diets were prepared: GML1 (0.25 g), GML2 (0.50 g), GML3 (0.75 g), and GML4 (1.00 g). Each diet was given to triplicate tanks containing 50 shrimp, each weighing 1.67 ± 0.25 g. GML2 supplementation enhanced the final body weight, weight gain, condition factor, specific growth rate, and viscerosomatic index of the shrimp compared to the other diets (p < 0.05). The whole-body amino acid profile was significantly high in the GML3 group. The antioxidant and immune indicators in the serum, like total protein, triglyceride, and aspartate aminotransferase, were significantly high in the GML2-supplemented group. The immune and antioxidant indicators in the hepatopancreas of the shrimp, like total protein, triglyceride, total cholesterol, and complement protein 3, were significantly high in the GML2 group. However, the malondialdehyde in their livers and serum were significantly high in the control group. Digestive enzymes were significantly high in the GML2 group. In conclusion, this study confirms that GML may benefit the health of Pacific white shrimp, offering new insights into aquaculture.

The mud crab Scylla paramamosain is a key economic crab species along the southern coastal regions of China. This study systematically compared the physiological and biochemical characteristics of low-temperature (LT) and normal-temperature (NT) strains of S. paramamosain at different life stages (juveniles and adults), integrating temperature gradient experiments with conventional aquaculture evaluations. The experimental results revealed the following: (1) Growth superiority: LT-strain crabs exhibited significantly greater final weight, survival rate, hepatopancreatic index, and gonadal index than their NT counterparts (p < 0.05). Moreover, LT individuals displayed an enhanced nutritional profile, with 16.56% higher muscle crude fat and a 23.80% increase in ovarian ash content. (2) Immune competence: Juvenile LT crabs exhibited greater antioxidant capacity at 18–21 °C, with significantly higher total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity than NT crabs (p < 0.05). In adults, immune enzyme activity remained superior, particularly in serum acid phosphatase (ACP). (3) Nutritional advantage: LT mature females exhibited higher accumulation of essential amino acids (e.g., lysine, threonine) and polyunsaturated fatty acids (C18:2n-6, C20:2n-6) in the hepatopancreas and gonads (p < 0.05). These findings confirm the LT strain’s superior cold resilience and aquaculture potential, offering practical insights for S. paramamosain selective breeding programs and sustainable aquaculture development.

An experimental ecological method was used to study the effects of water temperature, photoperiod, and light intensity on the survival, feeding, and growth of juvenile Schizothorax irregularis and Diptychus maculates. The Box–Benhnken experiment was designed to predict the optimal environmental conditions for juvenile growth. With the maximum specific growth rate at 15 °C and a photoperiod of LD16:8, the results demonstrated that the juvenile S. irregularis had a survival rate of over 85% in water temperatures ranging from 5 to 25 °C. A daily light duration of 15.86 h and a light intensity of 1166.28 lx, with the water temperature maintained at 10.45 °C, allowed the juvenile S. irregularis fish to attain the optimal circumstances for growth and survival. At water temperatures below 25 °C, the juvenile D. maculates exhibited maximum specific growth rates at 10 °C and LD16:8 light period. Additionally, as the light intensity reached 1000 lx, the juvenile fish grew better. Furthermore, the juvenile D. maculates fish achieved theoretically optimal survival and growth circumstances when the water temperature was maintained at 10.87 °C with a light period of 15.0.5 h per day and a light intensity of 1474.68x. The results showed that both fish species may be raised in captivity in highland regions, but precise control over water temperature is required.

The genus Cyprinus encompasses economically vital freshwater fish species; yet the phylogenetic relationships and evolutionary history of many taxa within this genus remain unresolved. To address this knowledge gap, we reconstructed the molecular phylogenetic and estimated divergence times using complete mitochondrial cytochrome b (CYTB) sequences of 76 Cyprinidae specimens, within Cyprinidae, including 4 outgroup species. Phylogenetic trees were reconstructed using maximum likelihood (ML) and Bayesian inference (BI) methods, while divergence times were estimated using a Bayesian relaxed molecular clock approach. The results confirmed the monophyly of the genus Cyprinus. The relationships among C. (Cyprinus) multitaeniata, C. (C.) pellegrini, C. (C.) acutidorsalis, and three Erhai Lake species (C. (C.) longipectoralis, C. (C.) barbatus, and C. (C.) chilia) were resolved with strong support. Cyprinus (C.) multitaeniata is basal. The species in Erhai Lake form a monophyletic group, and C. (C.) acutidorsalis is at the top of the phylogenetic tree. The taxonomic delineation within the genus Cyprinus remains controversial, particularly regarding the proposed division into two subgenera (Cyprinus and Mesocyprinus), which has been historically constrained by limited specimen availability for Mesocyprinus. Our comprehensive phylogenetic analysis reveals significant evolutionary divergence patterns: The genus Cyprinus diverged from Carassius during the 56.9 Mya. Notably, the Erhai Lake radiation species (C. (C.) longipectoralis, C. (C.) barbatus, and C. (C.) chilia) originated during 2.03 Mya, while the Lake Biwa endemic C. (C.) haematopterus demonstrates 8.7 Mya. We identified a late Pleistocene speciation event (0.75 Mya) in C. (C.) acutidorsalis, coinciding with its adaptation to brackish water ecosystems. The native C. (C.) pellegrini of Xingyun Lake and Chilu Lake may have originated 4.8 Mya, when the ancient lake that its ancestral population inhabited became isolated. These findings provide robust molecular evidence supporting the recognition of two evolutionary distinct subgenera within Cyprinus.

Sulfamethoxazole (SMX), a commonly used sulfonamide antibiotic, poses a threat to aquatic life due to its widespread presence in the environment. This study aims to investigate the specific effects of SMX on the development of marine medaka (Oryzias melastigma) embryos and larvae. Marine medaka embryos were exposed to SMX at concentrations of 0 (solvent control group, SC group), 1 μg/L (low concentration group, L group), 60 μg/L (middle concentration group, M group), and 1000 μg/L (high concentration group, H group). The results indicated that SMX exposure significantly accelerated the heart rate of embryos (p < 0.0001) and shortened the hatching time while also causing anomalies such as reduced pigmentation, smaller eye size, spinal curvature, and yolk sac edema. SMX also led to a decrease in the total length of the larvae. The M group and the H group exhibited a significant increase (p < 0.05) in lipid accumulation in the visceral mass of the larvae. In the L group and the M group, there was a significant increase (p < 0.0001) in the swimming distance of the larvae. At the molecular level, SMX exposure affected the transcript levels of the genes involved in the cardiovascular system (ahrra, arnt2, atp2a1, and cacan1da), antioxidant and inflammatory systems (cat, cox-1, gpx, pparα, pparβ, and pparγ), nervous system (gap43, gfap, α-tubulin), intestinal barrier function (claudin-1), detoxification enzymes (ugt2c1-like), and lipid metabolism (rxraa) in the embryos to larval stage. The microbiome analysis showed that at the phylum level, exposure to SMX resulted in an increase in the abundance of Proteobacteria. Additionally, the abundance of Actinobacteriota significantly increased in the L group (p < 0.05). At the genus level, the abundance of Bifidobacterium significantly increased in the L group (p < 0.05), while the abundance of Vibrio significantly increased in the H group (p < 0.05). The alpha diversity analysis revealed a significant decrease in the Chao1 index in the L and H groups, indicating a reduction in microbial richness. The beta diversity analysis showed differences in the microbial communities of marine medaka larvae among different SMX exposure groups. This study elucidates the negative impacts of SMX on the development of marine medaka embryos and larvae and their microbial composition, providing a scientific basis for assessing the risks of SMX in marine ecosystems.

The transfer time of Atlantic salmon smolts from freshwater to seawater remains a challenge in aquaculture, with the “smolt window” referring to the optimal timeframe for seawater readiness. Our study monitored Atlantic salmon osmoregulatory adaptations during smoltification under continuous light (LL) and winter signal regime (6 weeks LD 12:12) followed by 6 or 8 weeks of constant light. Fish were subsequently reared in seawater for 8 weeks and subjected to a stress event of cyclic hypoxia at the conclusion of the trial. Significant differences in growth trajectories were observed between the LL and LD groups, with fish receiving the winter signal showing compensatory growth after seawater transfer. Gill Na+/K+-ATPase (NKA) activity, plasma ions, glucose, and cortisol levels confirmed the importance of the winter signal for seawater adaptation. Molecular markers, including nka isoforms, Na+-K+-2Cl− cotransporter (nkcc), cystic fibrosis transmembrane conductance regulator (cftr), and Na+/HCO3− cotransporter (nbc), showed distinct temporal expression patterns, particularly in gills and midgut. Notably, the LD group with delayed seawater transfer exhibited enhanced growth and improved hypo-osmoregulatory capacity. These findings underscore the advantages of a winter signal in smoltification and suggest that delaying seawater transfer for up to 8 weeks could be beneficial.

Walleye Sander vitreus is a valued sportfish in eastern North America, including the upper New River of Virginia, where individuals can grow to a large size (>7 kg). After construction of dams, especially Claytor Dam in 1939, the population declined and non-native walleye were stocked. Stocking of non-native walleye was stopped in 1997, and molecular marker data showed that the presumptive native population had persisted. To restore the native stock, selection of broodstock candidates bearing native marker alleles and hatchery-based augmentation have been practiced over a 20-year period. We evaluated the success of the marker-assisted selection and hatchery-based augmentation program. Marker-assisted selection of native New River walleye began with mean frequencies of marker alleles at microsatellite loci Svi17 and Svi33 of ~30%, and continuing selection has driven marker allele frequencies to ~65–70%. Numbers of walleye collected in fall gillnet and spring electrofishing surveys were responsive to augmentations with hatchery fish 2–3 years earlier. Stocking was not practiced in 2012–2013, and a decrease in walleye catch rates was noted in 2016, suggesting that the native New River walleye population still depends upon hatchery-based augmentation. We recommend the development of a small panel of single nucleotide polymorphism markers for more rigorous selection of broodstock representative of the native walleye population.

X-ray electron probe microanalyzer technology was used to study the microchemistry and habitat history of Coilia nasus collected from the Dawanzhou section of the Yangtze River between May and June 2023. The Sr/Ca ratio from the otolith core to the otolith diameter was low (640–1100 µm), representing the first stage of development. In the second stage, C. nasus exhibited two distinct types. The first type, which included individuals 5HK05 and 6HK03, exclusively inhabited brackish estuarine waters. The second type, comprising 13 individuals, resided in higher-salinity seawater environments (Sr/Ca > 7). Furthermore, individuals 5HK01, 5HK03, 5HK07, and 6HK05 displayed a phase with a high Sr/Ca ratio compared to other fish. Freshwater coefficient analysis indicated that C. nasus in the Dawanzhou water area was unlikely to continue upstream to Dongting Lake in the middle reaches of the Yangtze River but may have entered Poyang Lake through its mouth or reproduced in its upper reaches. Analysis of sexual maturity and migration history suggested that the Dawanzhou section primarily serves as a migration channel for C. nasus, with a potential spawning ground for this high-value fish located nearby.

This study aimed to investigate the effects of dietary melatonin supplementation on growth and diurnal non-specific immunity, antioxidant capacity, digestive enzyme activities, and circadian clock-related gene expression in crayfish (Procambarus clarkii). A total of 500 healthy juvenile crayfish (6.68 ± 0.31 g) were randomly distributed into five groups with four replicates each and fed five different diets supplemented with melatonin at 0, 25, 50, 75, and 100 mg/kg for 60 days. The results indicated that dietary supplementation of 50 mg/kg melatonin significantly increased the weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) of juvenile Procambarus clarkii. However, no significant differences were observed in the hepatosomatic index (HSI), meat yield, and condition factor (p > 0.05). When the dietary melatonin level was 50 mg/kg, the activities of LZM and ALP in the hemolymph of Procambarus clarkii were higher than the levels at both 15:00 and 03:00, while the activities of AST and ALT remained at lower levels during these two time points. It also significantly upregulated the mRNA expression levels of Clock, Per1, Cry1, Tim1, and Tim2 in the hepatopancreas (p < 0.05). Furthermore, dietary melatonin at 50 mg/kg significantly reduced the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the malondialdehyde (MDA) content across day and night (p < 0.05). No significant differences were found in acid phosphatase (ACP) at 15:00, alkaline phosphatase (ALP), and amylase (AMS) activities in the hepatopancreas and intestine at 3:00 among the groups (p > 0.05). At 15:00, supplementation with 50 mg/kg significantly upregulated Bmal1 mRNA expression (p < 0.05). Melatonin supplementation at 50–75 mg/kg resulted in significantly higher levels of TP, LZM, ALP, and CAT activities, as well as significantly higher mRNA expression of Clock, Bmal1, Cry1, Per1, Tim1, and Tim2 in the hepatopancreas at 3:00 compared to 15:00 (p < 0.05), with the opposite trend observed for MDA content (p < 0.05). No significant differences were found in ACP, ALT, and AST activities between 3:00 and 15:00 among the groups (p > 0.05). Thus, dietary supplementation of 50 mg/kg melatonin could promote the growth of juvenile Procambarus clarkii, enhance their non-specific immunity and antioxidant capacity during both day and night, increase the activities of digestive enzymes in the hepatopancreas and intestine, and regulate the expression of circadian clock-related genes.

Red mullet (Mullus barbatus), a prominent fish species in the Mediterranean Sea, is a fish with a particular abundance of unsaturated fatty acids and other nutrients, including a substantial quantity of minerals. The nutritive quality parameters (lipid quality indices, fatty acid profiles, and mineral content, along with proximate composition) of 75 red mullet samples collected from five distinct locations (L1–L5) in the North and South Euboean Gulf, Euboea Island (Evia), Greece, were examined. It was hypothesized that the different habitats may have an impact on each fish’s chemical composition. Proximate composition (protein, ash, moisture, fat, and minerals) and bioactive compound determination (total carotenoids, and vitamins A, E, and C) were conducted on the lyophilized fish samples. The protein and lipid content of the wet fillet varied substantially from 10.8 to 14.3 and 13.2 to 16.8% w/w, respectively. The samples exhibited statistically non-significant variation in the total SFAs and MUFAs (p > 0.05). The level of total PUFAs was above 30% in all the samples and no significant differences were observed between them. However, arachidonic acid (20:4 ω-6) was only detected in fish samples from two locations (i.e., L1 and L3). The concentrations of Fe, Na, Mg, K, Ca, Ag, Sr, Li, and Zn varied significantly (p < 0.05) in relation to the size of the fish samples. The highest concentrations of heavy metals were detected at the northern location (L5), indicating a possible negative correlation between size and arsenic concentration. The varied mineral composition and fatty acid content of the samples can be attributed to their distinctive biological characteristics (i.e., length and weight) and dietary environments.

Long-term selective fishing pressure often leads to miniaturization, smaller size, and early sexual maturity in many commercial fish species. To adapt, these species increase energy allocations toward maturation and reproduction, which can reduce population productivity and recruitment. However, how different fishing pressures affect reproductive investment and energy allocation between growth and reproduction remains unclear. In this study, we designed three size-selective harvesting strategies—large, random, and small harvests—to examine their effects on the growth and reproductive investment of marine medaka (Oryzias melastigma). We analyzed changes in length, weight, and gonad weight across different harvest times. Results showed that the “large harvest” group allocated more energy to reproduction, leading to miniaturization and earlier maturation, while the “small harvest” group focused more on growth, resulting in larger fish at the same age. This study provides experimental evidence on how size-selective harvesting alters reproductive investment in fish populations, offering valuable insights for the sustainable exploitation of fishery resources.

Serum proteins are essential for maintaining osmotic pressure, regulating pH, transporting metabolites, and supporting immune responses. Studying the effects of plant-based diets on these proteins is crucial to understanding their impact on fish health and immune function. Methods: This study was conducted in a recirculation system, with rainbow trout distributed across nine tanks and fed three diets: fishmeal (control), medium plant meal (MPM; 40% of fishmeal replacement), and high plant meal (HPM; 80% of fishmeal replacement). Plasma protein and plasma glucose levels were measured at the initial and final stages, under both fasting (24 h after fast) and postprandial (6 h after fed) conditions, to assess dietary impacts. Additionally, the hepatosomatic index (HSI) was calculated at the end of the experiment to evaluate potential liver adaptations to the diets. Results: The initial protein and glucose levels were similar across all groups. However, by the end of the treatment, the fishmeal-fed group showed significantly higher total protein and globulin levels, while the albumin levels remained consistent across diet types. A significant interaction between sampling time and dietary treatment in fish reduced the clarity of dietary effects on postprandial plasma glucose levels. Furthermore, the HSI was significantly lower in fish fed the high plant meal (HPM) diet compared to the fishmeal and medium plant meal (MPM) groups, suggesting potential metabolic adaptation in response to plant-based diets. Conclusions: Replacing fishmeal with plant-based proteins in rainbow trout diets reduces total globulin and protein concentrations but leaves albumin unaffected, alongside reductions in fasting and postprandial glucose levels. The low growth and different HSI in fish fed plant-based diets highlights potential liver stress, emphasizing the need for further research to optimize sustainable aquaculture feeds while maintaining fish health and performance.

Antimicrobial peptides (AMPs) are biocompatible and biodegradable, making them an attractive alternative to traditional antimicrobial agents and chemical preservatives. Here, a novel α-helix amphiphilic anionic AMP Lc149 was screened from a large yellow croaker (Larimichthys crocea) using a Bacillus subtilis expression system. Lc149 is a hypothesized protein fragment not annotated in the genome of a large yellow croaker. Both extracellular protein and recombinant Lc149 (rLc149) exhibited significant killing effects against Gram-negative Escherichia coli and Vibrio harveyi. Scanning and transmission electron microscopy revealed that rLc149 had the ability to disrupt bacterial cell membranes, causing irregular cell morphology, severe cell membrane damage, cytoplasm agglutination, and intracellular content leakage. Confocal laser scanning microscopy and flow cytometry further confirmed bacterial cell destruction and mortality rates of over 80%. Gel retardation assays and SDS-PAGE electrophoresis showed that rLc149 was unable to bind to bacterial DNA, but did reduce bacterial protein contents. Additionally, rLc149 maintained antibacterial activity against E. coli and V. harveyi upon exposure to temperatures of 25–100 °C, UV radiation time of 0–60 min, pH levels of 3–12, and different proteases. Biosafety assays revealed low hemolytic toxicity to erythrocytes of large yellow croaker, rabbit, and shrimp, and low cytotoxicity to large yellow croaker kidney cells and HEK 293T cells. More deeply, rLc149 also possessed significant killing activity against parasites. Therefore, rLc149 can be considered an antibacterial and antiparasitic drug in fisheries.

This study investigates the relationship between Human Trophic Level (HTL) and trade openness within the context of seafood consumption patterns. Utilizing a comprehensive panel dataset spanning from 1990 to 2019 and covering 168 countries, this study applied fixed effects and random effects models to uncover the dynamics between trade openness, seafood diversity, and socioeconomic factors. The findings reveal a significant positive correlation between trade openness and HTL, demonstrating that increased access to diverse and high-trophic-level seafood products fosters improvements in national HTL. Additionally, economic development exhibits a non-linear relationship with HTL, where higher income initially drives a preference for high-trophic-level species, but dietary patterns diversify at advanced income levels. This study also highlights geographic disparities, with landlocked countries benefiting most from trade openness, whereas island and peninsula nations are influenced more by geographic and economic factors. These insights underscore the pivotal role of trade in shaping sustainable seafood consumption and provide actionable guidance for policymakers aiming to align economic growth with ecological sustainability.

Aquaculture plays a crucial role in meeting the needs of a growing human population and achieving the sustainable development goals outlined in Agenda 2030. However, it is essential that this sector grows sustainably. In this study, we hypothesized that environmental sustainability decreases as the trophic level of farmed species increases and that it is higher in integrated systems compared to monocultures. To test these hypotheses, we conducted a comparative analysis of the environmental sustainability indicators of some aquaculture systems, including the farming of primary producers, filter feeders, and low-trophic phagotrophs. We compiled secondary data on eighteen environmental sustainability indicators from seven aquaculture systems. Five are monocultures, including the farming of macroalgae (Hypnea pseudomusciformis), oysters (Crassostrea gazar) in a tropical environment, oysters in a subtropical environment, as well as tambatinga (hybrid Colossoma macropomum × Piaractus brachypomus) and tambaqui (Colossoma macropomum). Additionally, two are integrated systems: tambaqui raised in hapa nets (small cage-like enclosures) within Amazon river prawn (Macrobrachium amazonicum) ponds, and tambaqui and prawns cohabitating freely in the same ponds. A benchmark tool was utilized to establish reference values for comparing indicators between the systems, and a method was developed to create environmental sustainability indices that integrate all indicators. Environmental sustainability tends to decrease as trophic levels rise, supporting the initial hypothesis. However, the data revealed that Integrated Multi-Trophic Aquaculture (IMTA) systems ultimately have lower environmental sustainability than monocultures, which was contrary to our expectations. Algae and oyster farming were found to be more environmentally sustainable than low-trophic fish farming systems. Among these, the integrated systems did not demonstrate significantly greater sustainability than the monocultures, as initially anticipated. To gain a comprehensive understanding of sustainability, further research on the social and economic sustainability of these systems is necessary.

Cyprinid herpesvirus 2 (CyHV-2) is a major pathogen posing a serious threat to crucian carp farming and has led to major economic losses in China’s aquaculture industry. This research aimed to explore how the CyHV-2-ORF41 protein influences viral replication. Firstly, we found that ORF41 overexpression in Gibel carp brain (GiCB) cells significantly enhanced CyHV-2 replication. Subsequently, GST pull-down and LC-MS/MS analyses were conducted to identify ORF41’s protein interactions. The results showed that ORF41 might interact with pyruvate dehydrogenase (PDH)-E1β, an enzyme connecting glycolysis to the tricarboxylic acid (TCA) cycle. Furthermore, ORF41 expression decreased the PDH-E1β levels, leading to pyruvate and lactic acid accumulation. Molecular docking and dynamics simulations confirmed a stable interaction between ORF41 and PDH-E1β. This research not only deepens our understanding of CyHV-2’s mechanisms of infection but also suggests potential targets for therapeutic strategies in aquaculture.