Understanding habitat use and connectivity in estuarine fishes is essential for effective conservation and management. In this study, otolith microchemistry was applied to investigate habitat use and connectivity of the estuarine catfish Genidens genidens across three estuaries in southeastern Brazil. A total of 58 individuals were analyzed using laser ablation inductively coupled plasma mass spectrometry, focusing on strontium-to-calcium (Sr:Ca) and barium-to-calcium (Ba:Ca) ratios. Variations in elemental ratios along otolith transects were used to infer individual ontogenetic patterns along the estuarine–marine gradient. Most individuals exhibited combined use of estuarine and marine environments, while trajectories restricted to freshwater were rare. The apparent complexity of chemical profiles tended to increase with age; however, this pattern disappeared after correction for size-related bias, suggesting that age itself did not significantly influence habitat-use transitions. These patterns are consistent with ecological plasticity and partial migration within populations of G. genidens, although they may also reflect exposure to variable environmental conditions. Sr:Ca ratios were useful indicators of salinity-related transitions, whereas Ba:Ca ratios provided complementary information associated with continental influence. Overall, this study highlights the applicability of otolith microchemistry for investigating habitat-use patterns in estuarine fishes and reinforces the ecological importance of estuaries for feeding, growth, and recruitment in G. genidens, while acknowledging inherent limitations related to environmental variability and proxy interpretation.

Understanding the reproductive physiology of marine fish is critical for sustainable fisheries management, particularly under environmental variability. This study evaluated seasonal changes in body parameters (condition factor, Kn, and gonadosomatic index, GSI, as proxies for body condition and reproductive status, respectively) and biochemical composition (P, proteins; G, glucose; L, lipids; fatty acids; and bioenergetic ratios L/P, LG, all as proxy of integrated biochemical condition) of female gonads in Strangomera bentincki, a key pelagic species in the Humboldt Current System (HCS) off south-central Chile. Moreover, environmental factors (sea surface temperature and chlorophyll-a) were also analyzed to explore their influence on the FA profile of gonads. Female body parameters showed significant seasonal variations, with high values of Kn and GSI in autumn and spring, respectively. The biochemical composition also revealed significant seasonal variation in protein and glucose content, with the highest protein levels in winter and elevated glucose in autumn. While total lipid and energy content remained relatively stable across seasons, the L/P and L/G ratios presented seasonal variations. Similarly, the fatty acid composition showed pronounced seasonal differences, particularly with increased polyunsaturated fatty acids (e.g., DHA) in winter. The SST was the environmental factor with the greatest influence on the seasonal variations in the gonadal FA profile. Altogether, these findings suggest a partial capital breeding strategy in S. bentincki, where reproductive investment depends on both accumulated reserves and environmental conditions during reproduction. This study underscores the importance of incorporating reproductive biochemical indicators into ecosystem-based fisheries management models to improve assessments of stock health and reproductive potential.

The single mental barbel is a distinctive feature of the benthic Antarctic fishes of the «cryonotothenioid» subfamily Artedidraconinae. These barbels are unusual because their primary sensory modality is tactility, not chemosensation as in most other teleosts. They also exhibit considerable interspecific and intraspecific variation in length and in the appearance of the terminal expansion and its epidermis. Barbels range from short to long and the terminal expansion can be nonexistent, small and round, or large and oblong. In most species, the epidermal surface of the terminal expansion exhibits projections of various shapes and sizes. These range from smooth and furrowed, to ridged and furrowed, to pointed, to palmate (having lobes originating from a common point), and to fringed and leaf-like. Barbels are also subject to intraspecific variation among the species in the genera Dolloidraco, Histiodraco, Artedidraco and Pogonophryne. The various epidermal surface patterns all increase the sensory surface area exposed to the substrate and may enhance detection of their prey, primarily polychaetes. They also enhance surface roughness of the epidermis, thereby dissipating mechanical forces and providing some protection from abrasion by the substrate. The various patterns are likely an epigenetic response to different local conditions of the substrate. This variation warrants caution in their use as a defining taxonomic character.

This study aimed to investigate the effects of dietary tryptophan (Trp) on growth performance and muscle quality of Procambarus clarkii. Six experimental diets with graded Trp concentrations (0.05%, 0.13%, 0.29%, 0.43%, 0.56%, 0.69%; designated Trp0.05 to Trp0.69) were fed to crayfish for 8 weeks. Growth parameters, muscle proximate composition, texture, histology, related gene expression, and intestinal microbiota were measured. Compared with the Trp0.05 group, the Trp0.43 group significantly increased FW, WGR, SGR, and muscle crude protein content, while decreasing FCR. It also improved muscle texture (hardness, springiness, cohesiveness, gumminess, chewiness), increased muscle fiber diameter, and reduced fiber density and the proportion of fibers < 30 μm. Additionally, the Trp0.43 group upregulated mRNA expression of MEF2A, MEF2B, MLC1, MyHC, mTOR, S6K1, AKT, LARP6, Col1α1, Col1α2, TGF-β1, and Smad, and downregulated MSTN, 4EBP1, FOXO, and LC3. It reduced Proteobacteria and Shewanella abundance, and increased Bacteroidota and Firmicutes. In conclusion, appropriate dietary Trp improves P. clarkii growth, muscle quality, and intestinal microbiota. Based on quadratic regression analysis of WGR and SGR, the dietary Trp requirement of P. clarkii was estimated to be 0.39%, corresponding to 1.22% of feed protein.

The round sardinella (Sardinella aurita Valenciennes, 1847) is a widely distributed migratory pelagic fish inhabiting the Mediterranean Sea and the eastern Atlantic coasts. The species is heavily exploited and represents a valuable resource for global fisheries. In the Mediterranean area, uptakes of round sardinella are particularly high in the Ionian and Levant regions, where landings have shown fluctuating yet significant peaks in recent decades. Given its migratory nature, understanding the connectivity among populations is crucial for delineating appropriate fishery management units. Previous studies employing morphometric, meristic, and molecular analyses have yielded mixed results regarding population structuring. Here, the genetic differentiation among Eastern Mediterranean S. aurita populations was investigated using a multi-marker approach: the mitochondrial cytochrome c oxidase subunit I (COI), cytochrome b (CytB), control region (CR), and 16S ribosomal RNA (16S rRNA), and seven species-specific nuclear simple sequence repeats (SSRs). Overall, the results indicate high genetic diversity coupled with weak population structuring across the Eastern Mediterranean. These analyses aim at clarifying stock boundaries towards supporting sustainable management strategies at a regional scale for this ecologically and economically important species.

Background: Aquaculture, a vital component of global food security, faces sustainability challenges due to intensive farming practices, including water pollution, disease outbreaks, and antibiotic overuse. Probiotics, prebiotics, and synbiotics have emerged as eco-friendly alternatives to antibiotics. However, research results remain heterogeneous across aquatic species and intervention strategies. Methods: Following PRISMA 2020, we searched two databases (up to January 2026) for in vivo trials. Two reviewers screened and extracted data, and 177 eligible studies were ultimately included, covering single-/multi-strain probiotics (SSP/MSP), live/inactivated microbial preparations, and diverse synbiotic formulations. Results: Among 177 studies, Bacillus spp. were the most widely reported and effective probiotic strains. MSP and synbiotics exhibited superior efficacy in boosting aquatic animal growth performance and disease resistance over SSP in 68% of the included trials. Probiotics act through the competitive exclusion of pathogens, immune modulation, and enhanced digestive enzyme activity; prebiotics selectively stimulate beneficial gut microbiota, improving nutrient absorption and immune function through metabolites such as short-chain fatty acids; synbiotics combine the advantages of both, exerting synergistic effects. Furthermore, as water additives or fermented feed ingredients, probiotics reduce nitrogenous waste and organic pollutants, contributing to bioremediation. Conclusions: All three additives are effective. Standardized application protocols and long-term trials are needed for sustainable aquaculture. This review provides a unified evidence-based foundation for the rational use of these additives in aquaculture.

Viral and bacterial pathogen pathogens cause disease outbreaks that challenge the pearl gentian grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) industry’s sustainable development. The lack of monoclonal antibodies (mAbs) targeting serum immunoglobulin M (IgM) in this hybrid grouper impedes the development of non-lethal immunoassays for detecting pathogen infections, as well as research on immune responses following vaccination. We purified serum IgM from hybrid pearl gentian grouper and generated two mAbs—designated 41-H2-E1 and 62-E8-G9—against the purified IgM, finding that mAb 62-E8-G9 specifically recognized the IgM heavy chain, whereas mAb 41-H2-E1 specifically recognized the light chain. In indirect immunofluorescence assays, both mAbs reacted with surface Ig-positive (sIg+) lymphocytes. A double-antibody sandwich ELISA was subsequently established using mAb 62-E8-G9 as the capture antibody and HRP-conjugated mAb 41-H2-E1 as the detection antibody, enabling accurate quantification of serum IgM levels. Significant differences in IgM concentrations were observed between larger and smaller individuals (9.11 μg/mL vs. 3.84 μg/mL, p < 0.05). In immunostimulant administration experiments, both low-and high-dose groups exhibited approximately 2.0-fold higher IgM levels than the control group (p < 0.05). In contrast, vaccination with inactivated vaccines did not result in statistically significant differences in total IgM levels. mAb 41-H2-E1 was further applied to detect Vibrio parahaemolyticus- and Vibrio harveyi-specific immunoglobulins in serum under different vaccination regimens. Collectively, these findings demonstrated that the mAbs developed in this study served as reliable immunological tools for investigating immune function in hybrid pearl gentian grouper.

The successful establishment of non-native fish often relies on life-history plasticity and opportunistic trophic strategies. This study elucidates the invasion mechanisms of the non-native yellow catfish (Pelteobagrus fulvidraco) in Lake Erhai, a plateau lake in China, by integrating morphometrics, stable isotope analysis, and DNA metabarcoding. Our results reveal a “triple mechanism” driving this invasion success. First, the population exhibits significant phenotypic plasticity, manifesting as enhanced somatic growth and superior body condition (mean condition factor: 1.92) and sexually dimorphic growth favoring males. Second, DNA metabarcoding confirms a broad trophic niche dominated by zooplankton (31.70%) and, critically, other non-native fishes (Hypomesus nipponensis and Neosalanx taihuensis), providing strong empirical support for the synergistic effects of multiple non-native species. This predation on high-energy forage fish likely fuels the observed somatic growth and high reproductive output, counteracting the typical size-reduction trade-offs often seen in biological invasions. Third, reproductive assessment indicates a protracted spawning period (spanning at least from spring through summer) and an absolute fecundity (mean: 8471 ± 2194 eggs) consistent with its strategy of producing larger, high-quality eggs, significantly exceeding that of native riverine populations. These findings suggest that P. fulvidraco effectively exploits altered food webs—specifically pre-existing invasive prey—to maximize somatic growth and reproductive output, thereby establishing dominance in the plateau lake ecosystem. Therefore, effective management strategies must go beyond single-species control and prioritize controlling pre-existing invasive forage fish to disrupt the facilitation pathway driven by ecosystem alteration by invasive species.

The growth performance of Penaeus monodon is often reduced when fishmeal is extensively replaced with terrestrial ingredients. This study evaluated the efficacy of a marine microbial biomass, NovaqPro™ (NQ), and inorganic mineral premixes in improving the performance of low fishmeal diets. Diets containing soybean meal, soy protein concentrate, and bloodmeal were formulated with fishmeal limited to 6%. Treatments included 10% NQ, an experimental inorganic mineral premix, a commercial mineral premix, and their combinations added to the low fishmeal control. A high fishmeal diet was also assessed as a benchmark of performance. NQ supplementation significantly improved shrimp growth, increasing weight gain by 78.7% compared with the low fishmeal control (2.77 vs. 1.55 g shrimp−1) and numerically improved by 25.3% compared with the high fishmeal diet (2.21 g shrimp−1). Similar responses were observed for FCR where NQ diets (1.47–1.68), as well as the high fishmeal diet (1.59), were superior to that of the control diet (2.02). Growth improvements were associated with increased feed intake and higher retention of protein and gross energy. In contrast, mineral premix supplementation did not improve growth, and weight gain was numerically reduced relative to the low fishmeal control. The NQ diet showed higher apparent digestibility of calcium, phosphorus, and magnesium compared with the high fishmeal diet. These results demonstrate that NQ is an effective mitigation strategy to reduce growth limitations associated with low fishmeal diets in P. monodon, without the need for additional inorganic mineral supplementation.

The Pantanos de Villa wetland, a protected Ramsar site in Lima, Peru, faces significant pressure from invasive species and urban pollution. This study provides a comprehensive evaluation of microhabitat use and trace-element bioaccumulation in the invasive crayfish Procambarus clarkii (Girard, 1852). We analyzed the physicochemical parameters of the microhabitat and measured the concentrations of macroelements (Na, Mg, P), trace metals (Cu, Zn, Al, Ni, Ti, Pb), and a metalloid (B) in water, sediment, and crayfish tissues (gill, hepatopancreas, and muscle) using ICP-OES. Additionally, we examined the growth pattern of P. clarkii through its length–weight relationships. A total of 171 individuals were recorded: 99 males and 72 females. Males were longer (13–15 cm), while females were heavier (18–21 g). Additionally, a positive correlation was observed in females between the size and weight of the hepatopancreas and abdominal muscle, whereas no significant link was found in males. Sediments had higher levels of the evaluated chemical elements, with Cu (28.26 mg kg−1) and Zn (66.88 mg kg−1) exceeding international quality guidelines, indicating a possible ecotoxicological risk. The significant negative correlation between dissolved oxygen and the abundance of P. clarkii suggests that higher D.O. is associated with less bioturbation and more predators, making the microhabitat less suitable for juveniles. We conclude that P. clarkii serves as an essential bioindicator and potential vector for the relocation of the trace in an urban wetland, highlighting the need for integrated management strategies to reduce the ecological impacts of this invasive species.