Journal of fish biology最新文献

The Atlantic wolffish (Anarhichas lupus) is a cold-water fish with potential for aquaculture diversification. To unveil the mechanisms underlying the compromised growth in Atlantic wolffish when reared at higher temperatures, we investigated the relationship between temperature, growth rate, aerobic capacity, stress biomarkers, and gut barrier function. Juveniles acclimated to 10°C were maintained at 10°C (control) or exposed to 15°C for either 24 h (acute exposure) or 50 days (chronic exposure). Fish exposed to 15°C exhibited reduced growth, higher standard, and maximum metabolic rates compared to those at 10°C. In the chronically exposed group at 15°C, metabolic rates were lower than those of acutely exposed fish. The absolute aerobic scope exhibited no significant variation in temperatures; however, the factorial scope showed a notable reduction at 15°C in both acute and chronic exposed groups, aligning with a correlated decrease in individual growth rates. Chronic warming led to increased plasma glucose levels, indicating energy mobilization, but cortisol levels were unaffected. Furthermore, chronic warming resulted in reduced intestinal barrier function, as evidenced by increased ion permeability and a negative potential in the serosa layer. We conclude that warming elevates metabolic rates while reducing intestinal barrier function, thus increasing energy expenditure, collectively, limiting energy available for growth at this temperature from increased allostatic load. Thus, juvenile wolffish maintaining their aerobic scope under thermal stress experience slower growth. This research provides insights for improving the welfare and resilience of wolffish in aquaculture at elevated temperatures and understanding their response to increased environmental temperatures.

Fish visceral waste, which is normally discarded, is considered one of the richest sources of proteinases with potential biotechnological applications. For this reason, alkaline proteinases from viscera of Argentine hake Merluccius hubbsi, Brazilian flathead Percophis brasiliensis, Brazilian codling Urophycis brasiliensis, and stripped weakfish Cynoscion guatucupa were characterized. Individuals were caught by a commercial fleet off the coast of the Argentinean Sea. The intestine and pyloric caeca were dissected out and then minced and triturated with distilled water. The proteinase activity of P. brasiliensis extracts was enhanced by all the ions tested (Mn²⁺, K⁺, Na⁺, Ca⁺²) while the enzymes of the other species were stable in the presence of those ions, retaining more than 60% of their enzymatic activity. Alkaline proteinases of all species showed extreme stability to 5% v/v surfactants at 60 min (Sodium dodecyl sulfate, Triton X-100, Tween 20, Tween 80), and relative stability toward an 6% v/v oxidizing agent (H₂O₂) and organic solvents 80% (acetone, isopropanol, methanol, ethanol). The enzyme extracts were incubated for 60 min with these compounds. Interestingly, alkaline proteinases from all species were compatible with the commercial detergents (Ala, Skip, and Ace). These results demonstrate that proteinases recovered from a no-cost sample such as fishery residues can be used for industrial applications, such as detergent formulations.

The diamond stingray (Hypanus dipterurus) is a species of cartilaginous fish that, according to the IUCN, is globally in a vulnerable state of conservation and its populations show a decline. New records of this ray species in southern Peru and northern Chile have expanded their known range. The species is distributed in the Eastern Central Pacific, from southern California to San Andres, on the central coast of Peru, but is poorly known in Chile. Angler records mined from social media and historical data confirmed the presence of H. dipterurus along southern Peru and northern Chile, extending southward over 1250 km. A species distribution model (SDM) based on previous global occurrences combined with oceanographic layers was built to identify areas of potential and undocumented presence of H. dipterurus. The SDM showed high accuracy (area under the curve = 0.95) and predicted the potential presence of H. dipterurus along vast areas of the Peruvian and Chilean coasts, where the presence of the species was poorly documented. Comprehensive surveys are required to understand the distribution, population dynamics, habitat requirements, and threats to effective conservation efforts in the southern region of its distribution range.

The study investigated the potential alleviating effect of sodium butyrate (SB) on intestinal injuries caused by glycinin in the diet of common carp. Fish were divided into six groups: a control group (without glycinin and SB), a Gly group (with glycinin), and four groups supplemented with different doses of SB (0.75, 1.50, 2.25, and 3.00 g/kg) based on the Gly group. All diets were isonitrogenous and isoenergetic, and the fish were fed these diets for 8 weeks. The results indicated that glycinin activated the mitogen-activated protein kinase (MAPK) signaling pathway, leading to upregulating ERK, JNK, and p38 gene expression in the intestine. However, SB2 and SB3 groups were able to inhibit this pathway. Furthermore, glycinin upregulated the expression of proapoptotic genes (Bax, Caspase-3, Caspase-8, and Caspase-9) while downregulating the antiapoptotic gene Bcl2. The SB2 and SB3 groups were found to alleviate glycinin-induced apoptosis. Additionally, dietary glycinin significantly decreased the expression of tight junction genes (ZO-1, Claudin3, Claudin7, and Occludin1) in the intestine, whereas the SB2 and SB3 groups improved intestinal barrier function. Glycinin also elevated serum levels of d-lactate, diamine oxidase, serotonin, and endothelin, resulting in intestinal damage and increased permeability. In contrast, the SB2 and SB3 groups reduced these serum levels, thereby regulating intestinal permeability. Moreover, glycinin disrupted the intestinal morphology, which was mitigated by the SB2 and SB3 groups by increasing the height and width of intestinal villi folds. Lastly, dietary glycinin altered the intestinal microecological balance by increasing Proteobacteria abundance and decreasing Clostridium and Bacteroidetes abundance. The SB2 and SB3 groups modulated the composition of dominant taxa by increasing Firmicutes and Acidobacteria abundance. Overall, SB was found to mediate the MAPK signaling pathway, apoptosis, upregulation of tight junction genes, maintenance of the intestinal physical barrier, and regulation of intestinal flora, thereby alleviating glycinin-induced intestinal damage.

A workflow for developing a cost- and time-efficient, single nucleotide polymorphism (SNP)-based assay for species and hybrid identification is described. In a reference set (n = 46), the developed assay identified individuals of two closely related species, the Atlantic salmon (Salmo salar L., n = 23) and brown trout (Salmo trutta, n = 23), with 100% accuracy. Furthermore, species and hybrid identification using field-collected embryos had 98.1% concordance (155/158) to more expensive and time-consuming methods that utilized multiple SNP markers. The method can be integrated into management and conservation plans to quantify species' spawning distribution and hybridization rates.

Active (i.e., intentional) fish sound production provides informative cues for numerous ecological functions, including larval recruitment or reproduction, and can facilitate monitoring and restoration. It is therefore important to have a holistic picture of actively soniferous tropical reef fish diversity, particularly in the face of growing threats such as noise pollution and habitat degradation. This study integrates fish biodiversity and sonifery datasets to assess the prevalence and ecological characteristics of actively soniferous tropical reef fishes. There are 258 known sound-producing species, which span 46 families, encompass a variety of life-history (e.g., lifespan) and distribution (e.g., depth) attributes, and include many vulnerable and commercially valuable species. Furthermore, up to 75% of tropical reef fish species are considered likely to produce active sounds. This synthesis should encourage a greater appreciation for active fish sound production in tropical reef environments and advance efforts to incorporate soundscape ecology into management and restoration strategies.

Ideally, protection of a threatened fish will lead to their recovery in abundance, distribution, and size structure within the population, to a point where they are no longer considered threatened. Monitoring abundance and size is crucial to evaluate this, although low numbers associated with being threatened can strongly constrain the methods used. To assess if population recovery is occurring for the black rockcod Epinephelus daemelii, a large subtropical grouper endemic to shallow reefs in the southwest Pacific, surveys were undertaken across northern New South Wales and Lord Howe Island using roving diver timed counts and diver stereo-video measurements to assess relative abundance and length. Surveys in 2023 were compared with initial baseline data captured in 2009-2011 using the same methods. Relative abundance of E. daemelii at long-term monitoring sites has remained relatively constant or declined since 2010 rather than increasing. Comparisons between 84 broadscale sites in 2009-2011 versus 2023 (117 vs. 69 observed E. daemelii) indicate a recent decline in abundance. Although protected from fishing and spearfishing for over 40 years, the relative abundance of E. daemelii does not appear to be increasing over the past 15 years since monitoring commenced. This is a concerning trend that does not indicate recovery, although an increase in the proportion of mature females in the population from 2010 to 2023 is positive. As E. daemelii is slow growing, long lived, late to mature and still susceptible to incidental capture mortality, more active management may be needed to help assist with the slow recovery of this threatened species.

Here, we provide the first in situ observations of foraging habitats of Chaetodon daedalma, which is endemic to the subtropical north-west Pacific. Overall, 62.4% of bites were from the substratum, 30.7% from scleractinian corals, 3.3% from crustose coralline algae, 2.1% from macroalgae, and 1.2% from hydroids. The range in the percentage of bites taken from scleractinian corals among individuals was 0%-76%, and no fish fed exclusively on coral. Our in situ feeding observations confirm that the species is a facultative corallivore.

Wild Atlantic salmon migrate to sea following completion of a developmental process known as parr-smolt transformation (PST), which establishes a seawater (SW) tolerant phenotype. Effective imitation of this aspect of anadromous life history is a crucial aspect of commercial salmon production, with current industry practice being marred by significant losses during transition from the freshwater (FW) to SW phase of production. The natural photoperiodic control of PST can be mimicked by exposing farmed juvenile fish to a reduced duration photoperiod for at least 6 weeks before increasing the photoperiod in the last 1-2 months before SW transfer. While it is known that variations in this general protocol affect subsequent SW performance, there is no uniformly accepted industry standard; moreover, reliable prediction of SW performance from fish attributes in the FW phase remains a major challenge. Here we describe an experiment in which we took gill biopsies 1 week prior to SW transfer from 3000 individually tagged fish raised on three different photoperiod regimes during the FW phase. Biopsies were subjected to RNA profiling by Illumina sequencing, while individual fish growth and survival was monitored over 300 days in a SW cage environment, run as a common garden experiment. Using a random forest machine learning algorithm, we developed gene expression-based predictive models for initial survival and stunted growth in SW. Stunted growth phenotypes could not be predicted based on gill transcriptomes, but survival the first 40 days in SW could be predicted with moderate accuracy. While several previously identified marker genes contribute to this model, a surprisingly low weighting is ascribed to sodium potassium ATPase subunit genes, contradicting advocacy for their use as SW readiness markers. However, genes with photoperiod-history sensitive regulation were highly enriched among the genes with highest importance in the prediction model. This work opens new avenues for understanding and exploiting developmental changes in gill physiology during smolt development.