Search Results (1,060)

The replacement of fishmeal with plant-based ingredients in aquafeeds, while economically and environmentally advantageous, can impair lipid metabolism and liver function in fish due to the lack of specific bioactive compounds such as bile acids (BAs). BAs are amphipathic steroid molecules that facilitate lipid digestion and act as signaling hormones, yet their optimal inclusion levels in conventional, balanced diets for Nile tilapia (Oreochromis niloticus) remain undefined. This study evaluated the effects of dietary BA inclusion on growth performance, feed efficiency, body composition, and serum biochemical parameters of juvenile Nile tilapia (GIFT strain, initial weight 18.04 ± 3.67 g) and estimated the optimal inclusion level. Six isoproteic (320 g kg⁻¹) and isoenergetic (3300 kcal kg⁻¹) plant-based diets were formulated with increasing BAs levels (0, 50, 100, 200, 400, and 600 mg kg⁻¹) and fed to quadruplicate groups for 45 days. Only the Linear Response Plateau (LRP) model converged for weight gain data, estimating the optimal BA level at 479.70 mg kg⁻¹, with a plateau weight gain of 76.60 g. Inclusion of the 50–600 mg kg⁻¹ BAs significantly improved specific growth rate (up to 4.53%), crude protein retention efficiency (up to 81.11%), and whole-body crude protein content (up to 50.52%) compared to the control (p < 0.05). Fish fed 200 mg kg⁻¹ BAs exhibited the highest protein retention and lowest ether extract deposition, indicating a protein sparing effect. Serum lipase activity increased proportionally with BAs levels, while alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were reduced at 400 mg kg⁻¹ BAs, reflecting improved liver health. No mortality was recorded. In conclusion, dietary BAs inclusion enhances growth, protein utilization, and hepatic function in juvenile Nile tilapia fed plant-based diets. The recommended optimal level is 479.70 mg kg⁻¹ (dry matter basis), although significant benefits already occur from 50 mg kg⁻¹. These findings support the strategic use of BAs to improve the sustainability and efficiency of tilapia production. Full article

The silver pomfret (Pampus argenteus) is a high-value marine food fish, but its aquaculture is limited by juvenile intestinal immaturity, characterized by impaired digestion, barrier dysfunction, and microbial dysbiosis. This study evaluated whether early-life dietary inulin could improve intestinal health and muscle nutritional composition. After an 8-week feeding trial, fish fed a 5 g/kg inulin-supplemented diet showed improved growth performance, as reflected by higher final body weight (+17.2%), WGR (+18.5%), and SGR (+6.4%) than the control group. These benefits were associated with enhanced intestinal morphology, increased α-amylase and lipase activities, upregulated expression of tight junction genes, and a remodeled gut microbiota. These gut-associated changes were accompanied by improved selected muscle compositional traits. Specifically, inulin supplementation enriched essential amino acids, including methionine and threonine, as well as flavor-related amino acids, such as glutamate, glycine, and serine. Meanwhile, the muscle lipid profile was also modified, as reflected by reduced levels of selected saturated fatty acids and increased levels of monounsaturated fatty acids, particularly oleic acid. Collectively, our findings suggest that early-life dietary supplementation with 5 g/kg inulin may support intestinal homeostasis-related indicators and improve selected muscle nutritional traits in farmed silver pomfret. Full article

Reducing reliance on supplemental fish oil is central to sustainable aquaculture, but the molecular consequences of replacing it with vegetable oils remain poorly characterized in the juvenile Chinese soft-shelled turtle (Pelodiscus sinensis). We evaluated whether full substitution of the supplemental dietary fish oil (FO) with linseed oil (LO) or soybean oil (SO) compromises hepatic lipid metabolism in Pelodiscus sinensis. Three isonitrogenous and isolipidic diets, sharing identical fish meal and other ingredient bases and differing only in the supplemental lipid (4% FO, LO or SO), were fed to triplicate groups of juvenile turtles (initial body weight 55.0 ± 0.05 g) for 8 weeks. Growth performance, survival, feed conversion ratio, and serum biochemistry were unaffected. However, both vegetable oil diets altered tissue fatty acid composition, raising n-6 PUFA and lowering n-3 LC-PUFA and the n-3/n-6 ratio in liver and muscle (muscle EPA and DHA each decreased by approximately 40%); the SO group additionally exhibited elevated hepatic malondialdehyde, whereas hepatic lipid droplet area and lipid content did not differ significantly among groups. Liver transcriptomic profiling identified 262 (LO vs. FO) and 214 (SO vs. FO) differentially expressed genes, converging on lipid storage and bile acid metabolism. RT-qPCR confirmed the up-regulation of PLIN3, G0S2 and APOF and the down-regulation of CYP7A1. Over 8 weeks, replacement of supplemental FO maintained growth without overt impairment while altering tissue fatty acid profiles and the hepatic expression of key lipid metabolism genes. Full article

Curcumin (Cur), a polyphenol with excellent antioxidant and anti-inflammatory properties, is widely used in aquaculture. However, its low water solubility limits bioavailability. This study first investigated the effects of a highly water-soluble and bioavailable valine-curcumin (Val-Cur) on growth performance, antioxidant capacity, inflammatory factor expression and gut microbiota in juvenile largemouth bass. A total of 450 healthy largemouth bass (initial weight 12.00 ± 0.45 g per fish) were randomly divided into six groups: the basal diet group (CK), the group supplemented with 60 mg/kg of curcumin (Cur), and groups that were fed with 15, 30, 60, and 120 mg/kg of Val-Cur. Each group had three replicates (25 fish per replicate). After 8 weeks, compared with both the CK and Cur groups, 30–60 mg/kg Val-Cur displayed significantly increased growth rates, specific growth rates, and protein conversion efficiency, and significantly decreased the feed conversion ratio. Quadratic regression analysis indicated that the optimal supplementation level was approximately 51.62 mg/kg Val-Cur. The Cur and Val-Cur between 30 and 60 mg/kg groups also displayed significantly improved serum biochemical indicators (↑HDL-C, ALB, LZM, CAT and SOD, and ↓MDA). These groups also promoted the expression of intestinal anti-inflammatory factors (TGF-β1 and IL-10) and physical barrier genes (Claudin1, Occludin and Claudin4). In terms of regulating the intestinal microbiota, both Cur and Val-Cur significantly reduced the bacterial diversity (↓Sobs, Chao1 and PD indices) and increased the evenness of bacterial distribution (↑Simpson, Shannon and Pielou indices). In addition, the abundance of some potential pathogens (e.g., Plesiomonas, Plesiomonas shigelloides, and Pseudomonas fluorescens) significantly decreased, while the abundance of beneficial bacteria (e.g., Faecalibaculum, Faecalibaculum rodentium and Lactobacillus murinus) significantly increased. Pearson’s correlation analysis showed that the increase in the abundance of beneficial bacteria was positively correlated with improvement in growth performance, serum biochemical and antioxidant capacity indicators. In summary, Val-Cur exerted superior biological effects at lower dietary inclusion levels than Cur. This study laid a theoretical foundation for elucidating the mechanism of Val-Cur in improving fish immunity and promoting the application of water-soluble curcumin in aquaculture. Full article

Hydrogen-rich water (HRW) has growth-promoting, antioxidant, anti-inflammatory, and microbiota-modulating properties; however, its effects on juvenile snakeheads (Channa argus) remain underexplored. In this experiment, we investigated the effects of HRW on the antioxidant capacity, immune response, and gut microbiota of juvenile snakeheads. A total of 360 fish (15.32 ± 0.50 g) were randomly assigned to three groups: a control group (aerated water), a low-hydrogen group (H1, 280 ± 50 ppb), and a high-hydrogen group (H2, 550 ± 50 ppb). The results revealed that, compared with the control group, H1 significantly reduced serum levels of total protein, triglycerides, glucose, and urea nitrogen (P < 0.05). In the liver, H1 upregulated tir-2 expression and downregulated tnf-α expression (P < 0.05). Furthermore, serum SOD activity was significantly increased in both H1 and H2 groups compared with the control (P < 0.05), while serum CAT activity was significantly elevated only in the H2 group (P < 0.05). No significant alteration was detected in intestinal morphology (P > 0.05), and similarly, digestive enzyme activity did not change significantly (P > 0.05). Regarding gut microbiota, the H1 group increased the relative abundance of Actinobacteria (P < 0.05); at the genus level, it decreased the abundance of Acinetobacter and Pseudomonas, while increasing the abundance of Agathobacter, Faecalibacterium, and Anaerostipes (P < 0.05). In summary, our findings revealed that optimal HRW supplementation enhances immunomodulatory and antioxidant functions and improves intestinal health, thereby establishing HRW as a promising functional water conditioner for sustainable aquaculture applications. Full article

Lead (Pb) is a persistent aquatic pollutant that disrupts redox homeostasis in fish. This study investigated hepatic Pb accumulation, reactive oxygen species (ROS) production, antioxidant responses, lipid peroxidation, and transcriptomic alterations in juvenile pufferfish (Takifugu obscurus) exposed to waterborne Pb. Juvenile pufferfish were exposed to 5.98 mg/L waterborne Pb, corresponding to 10% of the 96 h LC50, for 96 h. Liver, blood, and hepatocyte samples were collected at 0, 12, 24, 48, and 96 h, with four biological replicates at each sampling time point. Hepatic Pb accumulation increased over time and reached the highest level at 96 h. ROS levels in blood cells and hepatocytes increased rapidly and peaked at 12 h. Superoxide dismutase (SOD) and catalase (CAT) activities showed early activation followed by late suppression, whereas glutathione peroxidase (GSH-Px) displayed partial adaptive recovery. Malondialdehyde (MDA) content increased progressively and reached approximately 2.8-fold of the control level at 96 h, indicating persistent lipid peroxidation. RNA-seq analysis identified 167, 460, 1398, and 2580 differentially expressed genes at 12, 24, 48, and 96 h, respectively. Enrichment, temporal trend, and weighted gene co-expression analyses indicated that Pb exposure shifted hepatic responses from early redox regulation to later metabolic adaptation, protein processing in the endoplasmic reticulum, proteasome function, and oxidative phosphorylation. qRT-PCR validation of 12 hub genes supported the RNA-seq results. These findings provide integrated biochemical and transcriptomic evidence for oxidative-stress-mediated hepatic toxicity in pufferfish exposed to waterborne Pb. Full article

Bacterial diseases occur frequently in freshwater aquaculture in China, highlighting the need for green immune preparations. Fucoidan and laminarin are commonly used feed additives in livestock and poultry industries; however, their application in freshwater aquaculture remains limited. In this study, juvenile Megalobrama amblycephala were fed diets supplemented with fucoidan or laminarin, each at 0.5% and 2% (w/w), for 8 weeks. After the feeding trial, fish were challenged with Aeromonas hydrophila. Cumulative mortality rate, tissue bacterial loads, innate immune and antioxidant enzyme activities, and immune-related gene and protein expression were evaluated. Dietary supplementation with 2% fucoidan significantly improved the growth performance and feed utilization of juvenile M. amblycephala, while 0.5% fucoidan and 2% laminarin groups only enhanced feed utilization. After A. hydrophila infection, cumulative mortality rates for the control, 0.5% and 2% fucoidan, and 0.5% and 2% laminarin groups were 76.67%, 67.78%, 57.78%, 62.22%, and 58.89%, respectively. Both supplements increased post-infection survival, reduced tissue bacterial loads, and enhanced host bactericidal and antioxidative abilities by elevating innate immune and antioxidant enzyme activities. Innate immunity of juvenile M. amblycephala was improved by regulation of immune-related gene and protein expression levels. Both additives demonstrated significant immunoprotective effects, markedly reducing mortality and tissue bacterial loads following infection. This study provides a theoretical foundation for developing green immunostimulants and antibiotic alternatives for bacterial diseases in fish. Full article

Plant-derived additives are increasingly explored as functional aquafeed ingredients for supporting fish performance and physiological condition. This study evaluated the effects of dietary Wedelia chinensis extract (WCE) on growth performance, feed utilization, antioxidant status, innate immune-associated biomarkers, and immune- and antioxidant-related gene expression in Nile tilapia (Oreochromis niloticus). Juvenile fish with an initial body weight of 14.31 ± 0.03 g were fed diets supplemented with WCE at 0, 5, 10, 15, or 20 g kg⁻¹ diet for eight weeks. Growth indices, somatic indices, serum and hepatic antioxidant biomarkers, mucosal and systemic innate immune-associated parameters, and liver and intestine gene expression were assessed. Dietary WCE improved final weight, weight gain rate, specific growth rate, and feed conversion ratio compared with the control, with WCE10 showing the most consistent growth-related response. Somatic indices were not significantly affected. WCE supplementation increased antioxidant enzyme activities and reduced malondialdehyde levels in serum and liver, particularly at moderate inclusion levels. It also increased lysozyme and peroxidase activities, alternative complement activity, phagocytic index, and respiratory burst activity, and modulated selected immune- and antioxidant-related genes in the liver and intestine. Taken together, dietary WCE, particularly at 10 g kg⁻¹ diet, improved growth and feed utilization while supporting antioxidant status and basal innate immune-associated biomarkers during the eight-week feeding trial, without detectable changes in somatic indices. These findings provide a basis for further evaluating WCE as a plant-derived functional additive for Nile tilapia aquafeeds under pathogen-challenge and practical farming conditions. Full article

Fish are an important criterion for evaluating the quality of river ecosystems, and water flow characteristics may be the main factor affecting the living environment of fish. As the main component of a river, the topography of the bank slope has a significant impact on the characteristics of nearshore water flow. At the same time, eco-revetment structure has the functions of smoothing water flow, maintaining stable bank slopes, and improving river ecology. It can reset the distribution of nearshore water flow and provide a stable living environment for fish. This study focuses on the middle and lower reaches of the Yangtze River as the research area, with the main research object being grass carp. We construct a generalized model based on river morphology and flow characteristics. A new eco-revetment structure is proposed with the main research area of nearshore waters, aiming to improve the flow state of nearshore water and enhance its ecology. A suitability evaluation model for grass carp habitat was constructed based on Large Eddy Simulation and fuzzy mathematics theory, with water flow as the main habitat influencing factor. We study the distribution pattern of suitability for grass carp habitats near nearshore waters. The results indicate that the nitrogen phosphorus ratio near the top of the revetment structure is close to the Redfield value and can be used as a stable foraging area for fish. The flow rate is the dominant factor for the habitat of juvenile grass carp. When there is no vegetation, the suitability of region A is 0–0.4, the suitability of region B is 0.2–0.6, and the area proportion of the high suitability area (0.4–0.6) is maintained at 10–30% with the increase in the flow rate. Region C is not suitable for the long-term survival of juvenile grass carp. When there is vegetation, the suitability of region A ranges from 0 to 0.6, and the proportion of low-suitability areas decreases. The suitability of region B ranges from 0.4 to 0.6, and the proportion of suitable areas is positively correlated with flow velocity. The suitability of region C is consistent with the absence of vegetation. The dominant factors for fish spawning habitat are flow velocity, vorticity, and kinetic energy gradient. The spawning suitability zone (HSI ≥ 0.6) is located between the spanwise structures, with a proportion positively correlated with flow velocity and higher suitability on the deep-water side. The existence of fish has little impact on the habitat. In the juvenile fish habitat area, the proportion of areas suitable for juvenile fish in region A has slightly decreased, and the suitability of region B has increased. In spawning grounds, an HSI ≥ 0.6 accounts for about 5% of the decrease compared to no-fish conditions, and overall can meet the needs of fish habitat, foraging, and spawning. This article provides ideas and foundations for the design of future new eco-revetment structures and a suitability analysis of living environments for fish. Full article

The replacement of fishmeal (FM) in aquafeeds for carnivorous fish remains challenging due to reduced palatability and adverse effects on liver health and intestinal microbiota. Marine by-products-based additives containing fish protein hydrolysates and seaweed polysaccharides have shown potential to overcome these limitations. This study evaluated the effects of graded supplementation of Haiweisu (HWS), a multi-marine by-product formulated with squid viscera hydrolysate, small-molecule components from fish protein hydrolysate, seaweed polysaccharides, and seaweed residue as a carrier, in a FM-free diet for juvenile largemouth bass. Four isonitrogenous and isolipidic diets were prepared: a FM-free control diet (CON) and three diets supplemented with 10, 20, or 30 g/kg HWS (designated S10, S20, and S30, respectively). Each diet was fed to triplicate groups of fish (29.26 ± 2.61 g) for 56 days. Results showed that HWS supplementation linearly increased final body weight, weight gain rate, and feed intake, while significantly reducing the feed conversion ratio (p < 0.05). All HWS-supplemented groups exhibited markedly lower hepatic lipid accumulation and plasma total cholesterol levels compared with the CON group, accompanied by alleviated hepatocellular steatosis and inflammatory infiltration as revealed by Oil Red O and H&E staining. Moreover, HWS significantly enhanced intestinal microbiota alpha diversity (Ace, Chao, Sobs, and Shannon indices), decreased the relative abundance of the dominant genus Mesomycoplasma, and enriched potentially beneficial genera including Methylobacterium, Delftia, and Sphingomonas (p < 0.05). In conclusion, dietary HWS supplementation effectively improved growth performance, alleviated hepatic steatosis and inflammation, and beneficially reshaped the intestinal microbiota in juvenile largemouth bass fed a FM-free diet. These findings support HWS as a promising functional additive for sustainable FM-free aquafeeds in carnivorous fish species. Full article

Introduction: The aglomerular kidney, characterised by the absence of functional glomeruli and reliance on tubular secretion alone, has evolved independently across multiple teleost lineages occupying diverse environments, including notothenioids of the Southern Ocean, gadids of cold North Atlantic and Arctic waters, and syngnathids distributed across temperate and tropical seas. Despite sharing this independently derived renal architecture, these groups face markedly distinct osmotic, thermal and chemical challenges in their natural habitats. How aglomerular kidneys cope with environmental stressors, including fluctuations in temperature and salinity, and how they handle the excretion of xenobiotics and other exogenous compounds through exclusively tubular mechanisms, remains poorly understood. The physiological and molecular responses underlying renal function in these lineages have received comparatively little attention relative to their glomerular counterparts. Objective: This study investigates how aglomerular kidneys across phylogenetically distinct teleost lineages respond, at molecular and physiological levels, to contrasting environmental conditions, namely temperature and salinity challenges predicted to alter the functional demands on renal osmoregulation. Methodology: Adult and juvenile specimens from target lineages were subjected to controlled exposure experiments combining different temperature and salinity regimes. Blood and urine samples were collected to assess osmolality and ionic composition. Renal tissues were processed for gene expression analysis of key transport and structural genes, histology, immunohistochemistry and enzymatic activity assays, providing an integrated picture of renal function under each condition. Results: Molecular analyses are currently underway. Preliminary work has established protocols for RNA extraction and quantitative PCR across target species, enabling comparative gene expression profiling to proceed across the full dataset. Conclusions: A comparative physiological and molecular approach across aglomerular teleost lineages will clarify whether shared renal architecture translates into shared functional responses to environmental challenge and identify lineage-specific mechanisms of renal adaptation, with broader relevance for predicting how these fishes may respond to ongoing environmental change. Full article

Introduction: Marine heatwaves are increasing in frequency and intensity, posing major challenges for fishes inhabiting shallow coastal ecosystems. Short-term exposure to extreme warming can alter metabolic performance and thermal tolerance, with potential consequences for species persistence and school composition in thermally variable habitats. Understanding the capacity of coastal fishes to withstand acute warming events is therefore essential for predicting ecological responses to climate change. Objective: We aimed to determine the effects of simulated marine heatwaves on thermal tolerance and metabolic performance in juvenile grey mullets, Chelon labrosus and Chelon aurata, two abundant sympatric species inhabiting the Ria Formosa lagoon (southern Portugal). Methodology: Juvenile mullets acclimated at 17 °C were exposed to simulated heatwave treatments of 23, 27, or 33 °C and sampled either at peak temperature or after 48 h and 1-week recovery at 17 °C. Critical thermal maximum (CTmax, using a 1 °C/min thermal ramp), static oxygen consumption (MO2), and intermittent respirometry parameters were measured. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) were derived from intermittent respirometry. A complementary temperature-ramp (>3 h at each temperature step 17, 23, 27 and 33 °C) was performed to evaluate routine metabolic rate and estimate Q10 values across increasing temperatures. Additional plasma and tissue analyses are being conducted to assess energetic substrate mobilization and cellular responses to thermal and oxidative stress. Results: CTmax increased significantly with warming in both treatment modes, demonstrating rapid heat hardening in juvenile mullets. Fish exposed to 27 and 33 °C exhibited higher CTmax than control fish, and this elevated tolerance persisted after recovery. Chelon labrosus showed slightly higher CTmax values than C. aurata. Oxygen consumption increased with temperature, with the strongest responses occurring at 33 °C. SMR increased markedly with warming, particularly in heatwave-exposed fish, while MMR increased mainly at the highest temperature treatment. In contrast, AS showed no clear thermal optimum or decline across treatments. Routine metabolic rate increased non-linearly with temperature in the complementary ramp experiment, with a mean Q10 of 2.28, confirming strong thermal dependence of metabolism. Conclusions: Juvenile mullets possess substantial short-term thermal plasticity and can rapidly increase heat tolerance during marine heatwaves but this enhanced tolerance is accompanied by elevated metabolic costs under extreme warming, indicating potential energetic trade-offs near upper thermal limits. Differential physiological responses between species may influence school composition and ecological performance across thermal landscapes. Ongoing plasma and tissue analyses will further clarify the energetic and cellular mechanisms underlying thermal and oxidative stress resilience in coastal fishes. Full article

The Iberian barbel (Luciobarbus bocagei Steindachner, 1864) is a potamodromous species that displays migratory movements, with adults moving upstream during spring to spawn, followed by downstream migration in autumn by both adults and juveniles to feed and inhabit more productive river stretches. Increasing river fragmentation due to dam construction and operation causes a loss of connectivity and suitable habitat, which can affect this natural behaviour. In a tributary of River Douro, River Tua, a 108 m high dam, was recently built (i.e., Foz Tua dam in 2017) at only 1.1 km from the river mouth, leaving the upstream spawning area inaccessible. To evaluate the species behavioural response to this impact, a passive acoustic telemetry array was deployed in the study area, and between 2018 and 2023, 120 tagged fish had their movements tracked. The results showed two different behavioural profiles in the same population with migratory (42.5%) and resident (54.0%) individuals. During this period, a specific experimental study was developed to evaluate the response of a subset of 90 fish, captured upstream of the Foz Tua dam and translocated to an alternative downstream Douro tributary (River Pinhão, ~20 km downstream from River Tua). From these, 66.7% remained at the release site, whilst 23.3% returned to the river of origin, i.e., River Tua. From the returned fraction, 28.6% of the tagged fish maintained this migratory behaviour between both rivers in the following years. Generalized Additive Models were used for each of the two behavioural profiles observed in this study, to identify which environmental variables were associated with the presence of the tagged barbels downstream the Foz Tua dam. Ecological flow, temperature and day-period were some of the predictors explaining the use of this river stretch downstream of Foz Tua dam. This study substantially updates the available information regarding this species’ movement patterns at large spatial and temporal scales, contributing to enhancement of management and conservation programs for potamodromous species, in highly impounded and fragmented rivers. Full article

Introduction: Establishing baseline descriptions of inorganic elements in the early life stages of sharks and in their respective nursery areas is essential for assessing anthropogenic impacts and supporting conservation strategies. Objectives: This study presents the first baseline of plasma trace element concentrations (Al, Zn, As, Cu, Cr, Cd, Co, Mn, Ti, Ni, Hg, Pb) for four juvenile shark species (Carcharhinus limbatus, Paragaleus pectoralis, Rhizoprionodon acutus, and Sphyrna lewini) from Sal Rei Bay, Boa Vista Island, Cabo Verde—the first multi-species shark nursery area described in Atlantic Africa. Methodology: Seawater and sediment samples were collected from eight sites and analyzed along with plasma samples using total reflection X-ray fluorescence spectroscopy (TXRF). Sediment granulometry and pollution indices, including the enrichment factor (EF), ecological risk index (RI), and metal pollution index (MPI), were used to characterize habitat contamination. Data were analyzed using statistical models to explore spatial and element-specific patterns. Results: Overall, environmental contamination was low, with slight increases in Cd, Co, and Hg at sites 1 and 2, near the fishing port, and at site 5, likely reflecting natural transport, sediment redistribution, and enhanced nearshore deposition. Juvenile sharks exhibited generally low plasma trace element concentrations, although species-specific elemental signatures were evident: elevated levels of Al and Cu in C. limbatus, Zn in S. lewini, and As in R. acutus and P. pectoralis. Conclusions: These findings establish critical baseline reference values for trace elements in juvenile sharks from a key Atlantic nursery area. The results provide an essential framework for future biomonitoring efforts and contribute to the management and conservation of Cabo Verdean shark nursery habitats. Full article

To evaluate the effects of swimming training on growth, swimming performance, and osmoregulatory-related indices in juvenile coho salmon, freshwater-reared fish were subjected to current of 1 body length per second (BL·s⁻¹) from December 2024 to April 2025. Fork length, body weight, condition factor, insulin-like growth factor-1 (IGF-1), and gill and intestinal Na⁺/K⁺-ATPase (NKA) protein abundance were measured monthly, and critical swimming speed (U_crit) was evaluated after one month of training. Trained fish showed greater fork length in March and higher body weight in March and April than controls. The condition factor was higher in trained fish in February and March, but declined during spring smolt development. Swimming capacity was enhanced by training, as indicated by significantly higher U_crit. Mean IGF-1 levels did not differ between groups, but IGF-1 correlated positively with body size only in trained fish. No significant training effect was detected for either gill or intestinal NKA protein abundance, although gill NKA increased significantly in April, likely reflecting seasonal smoltification. In addition, IGF-1 was significantly correlated with gill NKA in trained fish in March. Collectively, these results indicate that sustained swimming training improves growth and swimming performance and may enhance associations among measured physiological variables during smoltification in juvenile coho salmon. Full article