Aquaculture, Fish and Fisheries最新文献

Aquatic invasive species have negative impacts on native biodiversity and pose a significant threat to overall ecosystem health. Successfully established non-native species possess life history traits that are advantageous for colonization and expansion into novel environments. The reproductive traits and strategies of fish are often good predictors of invasion success. Thus, understanding reproductive dynamics of non-native species in their introduced environments is an important component for predicting expansion and effectively managing invasive populations. The Weather Loach Misgurnus anguillicaudatus is a recently discovered introduced species in Georgia, USA, and little is known about its life history attributes where it is not native. Thus, the objectives of this study were to: (1) estimate mean batch fecundity of female Weather Loach; (2) determine timing and periodicity of spawning; and (3) evaluate whether the gonadosomatic index (GSI) is a reliable indicator of reproductive status in this species. Based on observed peaks in eggs larger than 500 µm, we identified the presumed spawning season for Weather Loach to be occurring from April through August. The highest average fecundity observed was during July (10,539 eggs) and the lowest average fecundity observed was during April (3083 eggs). The GSI was a strong predictor of fecundity and tracked the number of mature eggs present in each month of the year. Our estimates of batch fecundity and determination of the annual spawning season can help managers better understand reproductive dynamics and develop predictive population models aimed at evaluating management activities.

Biofloc technology (BFT), an eco-friendly aquaculture system, was evaluated for its effects on growth performance, digestive physiology, gut microbiota, and carcass quality in juvenile common carp (Cyprinus carpio) using cane molasses as a carbon source at carbon-to-nitrogen (C/N) ratios of 15, 20, and 25. Compared to conventional intensive farming (control), carp reared in BFT systems (over 90 days) exhibited significantly improved growth performance, including weight gain, specific growth rate, and feed conversion ratio, particularly at C/N ratios of 20 and 25. The BFT groups also demonstrated enhanced digestive enzyme and antioxidant activity, higher proportion of beneficial lactic acid bacteria, and improved carcass composition. These findings indicate that BFT using sugarcane molasses at a C/N ratio of 20 offers a sustainable alternative to conventional carp farming. Beyond improving growth performance, BFT positively influenced fish health indicators and carcass quality.

Measurements of length and mass are used in many research fields, and such data are often collected from samples that have been preserved in ethanol or frozen prior to data collection. Since many preservation methods affect the size and shape of soft-bodied animals, species-specific correction factors are used. Here, we calculated ethanol and freezing shrinkage correction factors for the European eel, Anguilla anguilla Linnaeus, 1758, and investigated how preservation duration and individual size affected shrinkage. We also investigated if freezing had an impact on the size of the eyes and pectoral fins, which could affect maturation stage classification. We found that preservation in 95% ethanol and freezing decreased body length and mass, as expected. Time kept in ethanol did not affect shrinkage. Time kept in freezer had some effect on shrinkage, and the model fit suggested inclusion of days frozen for body mass shrinkage. That, however, only had negligible improvement on the model. For preservation in freezer, shrinkage was greater for lengths below 330 mm and mass below 100 g, compared to eels above these sizes. However, applying a size threshold to the analysis only generated negligible improvement of the model fit, meaning that specific shrinkage factors for different sizes are not needed. We also found that freezing induced shrinking in eye size, while the pectoral fin increased in size. The increase in pectoral fin length is however believed to be due to a measurement deviation. User-friendly formulas for all correction factors are provided. The application of these factors should be restricted to the European eel within the size range used in this paper.

The farming of Pacific oysters (Crassostrea [Magallana] gigas) is a rapidly growing industry in Alaska, where farms represent some of the highest latitude oyster cultivation efforts in the world. Little is known about the nearshore oceanography where Alaskan farms are located, or how the subarctic marine context influences oyster tissue quality. This research begins to elucidate those relationships and seasonal variation therein through regular sampling of water column parameters, phytoplankton community composition, and Pacific oyster tissue. Results suggest both benefits and challenges to cultivating Pacific oysters in this dynamic region in Alaska. Benefits included low temperatures that inhibited spawning, resulting in Pacific oysters with year-round high levels of lipids and polyunsaturated fatty acids. Challenges included a later onset of the spring phytoplankton bloom, resulting in a short growing season compared to other growing regions, occasional blooms of the harmful algal genus Alexandrium spp. that resulted in periods of elevated levels of paralytic shellfish toxins, and intensifying climate variability and ocean acidification. The results of this study provide a better understanding of nearshore dynamics in the estuarine environment of Southeast Alaska's inside waters, which will aid in future site suitability analyses and improve our understanding of cultivating Pacific oysters in this region. As increasingly extreme summer heatwaves contribute to oyster mortality events and other challenges at lower latitude farms, the relatively cold waters at Southeast Alaska oyster farms may offer a buffer against stressors associated with climate variability.

The cover image is based on the Original Article by Earthworm (Eisenia fetida) Meal as Fishmeal Replacement in the diet of Oreochromis niloticus (Linnaeus, 1758) fingerlings by Belay Abdissa et al., https://doi.org/10.1002/aff2.70105.

Gaps in knowledge exist regarding sperm quality in farmed fish and its variation with age. The literature shows differing results among populations with diverse genetic backgrounds. Data collected from captive mass-spawning Norwegian Arctic charr were analysed to investigate sperm quality parameters and their age-related variations. We conducted a retrospective review of 63 milt analysis records from broodfish aged 2–9 years. Sperm motility and kinetic parameters decreased significantly (p < 0.05) with advancing age, whereas no significant changes were observed in sperm concentration. A regression model explaining approximately 30% of the variation (adjusted R² ≈ 0.3) suggested a significant and negative effect of age on sperm swimming velocities (p < 0.05). Finally, the analysis of the ddRAD data did not reveal significant genetic associations. Overall, this study provides valuable insights into age-related trends and may serve as a foundation for further investigations into the sperm quality performance of populations with varying reproductive strategies and genetic structures.

Developing optimized feeding strategies for copepods is essential in contemporary aquaculture, as they serve as a highly nutritious live feed for numerous aquatic organisms. Three experiments were conducted to enhance the development and reproductive success of the copepod, Cyclops sp., to support sustainable aquaculture practices. The first experiment examined the effect of different initial stocking densities of Cyclops sp. (250 (CD250), 500 (CD500), 1000 (CD1000), 3000 (CD3000) and 6000 (CD6000) indv. L⁻¹) on the final growth where CD1000 supported the most favourable growth compared to CD6000 and CD500 (p = 0.008 for all comparisons) as well as CD3000 and CD250 (p < 0.001 for all comparisons). The second experiment evaluated the population responses of the Cyclops sp. to varying concentrations of Chlorococcum sp. (1 × 10⁵ (AC1), 3 × 10⁵ (AC3), 5 × 10⁵ (AC5), 7 × 10⁵ (AC7) and 9 × 10⁵ (AC9) cells mL⁻¹). The highest density of the Cyclops sp. was observed at AC5 than other concentrations (p < 0.01 for all comparisons). The third experiment investigated the influence of different dietary regimes (live Chlorococcum sp. (Alg), live Chlorococcum sp. + commercial yeast (Saccharomyces cerevisiae) (Alg + Y) and only commercial yeast (Y)). The significantly highest copepod density was achieved with the supplementation of the Alg + Y diet than others (p < 0.01). These results suggest that optimizing initial stocking densities and using relatively high concentrations of Chlorococcum sp. can effectively promote the growth and abundance of Cyclops sp. Furthermore, incorporating Chlorococcum sp. into the feeding regimens, either alone or in combination with other diets, improves the copepod growth and reproduction, providing valuable insights for optimizing aquaculture practices.

Phytogenic additives such as Tribulus terrestris are known to promote various beneficial effects. Although most well-documented benefits relate to reproductive performance, their consumption may also induce positive physiological effects. This study aimed to evaluate the effects of supplementing Nile tilapia diets with different concentrations of T. terrestris (200, 400, and 600 mg kg⁻¹) compared to a control group (0 mg kg⁻¹). The 32-day experiment was conducted in a recirculation system with 12 tanks, each treatment replicated three times, with 15 fingerlings per tank. We assessed zootechnical performance, enzymatic activities—including alanine aminotransferase (ALT), aspartate aminotransferase (AST), superoxide dismutase (SOD), catalase (CAT), amylase and alkaline phosphatase (ALP)—fish proximate composition (moisture, crude protein, crude fat and ash), and histomorphometric analyses of liver and intestine. Results showed no significant differences in zootechnical performance or carcass composition. However, enzymatic activities varied significantly: T. terrestris enhanced amylase and ALP activities at all supplementation levels; SOD activity increased at 200 mg kg⁻¹ but decreased at 600 mg kg⁻¹; ALT and AST levels were reduced across all supplemented groups compared to control. Muscle histomorphometric showed decreased fibre diameters with supplementation, suggesting inhibition of muscle hypertrophy. Overall, T. terrestris exhibited hepatoprotective effects and improved amylase activity but did not affect zootechnical performance. In conclusion, dietary supplementation with T. terrestris influenced enzymatic activities and muscle histomorphometry in Nile tilapia, notably enhancing amylase and ALP activities, which may improve dietary nutrient absorption.

Monitoring biodiversity changes over large spatiotemporal scales is critical for effective ecosystem conservation and management. This study investigates the potential of environmental DNA (eDNA) metabarcoding to enhance national-scale biomonitoring of freshwater diversity by leveraging discarded filters associated with routine water quality sampling from the U.S. Geological Survey's (USGS) National Water Quality Network (NWQN). We tested 375 samples from 103 NWQN sites for eDNA of native and non-native fish and found that 52% of the filters yielded fish eDNA for a total of 70 fish species detections. Of the filters that had fish eDNA present, an average of 3.7 species were detected. Benchmarking these results to USGS's Aquatic Gap Analysis Project (AGAP)—which includes both field-verified observations along with predictive models derived from fish capture and landscape predictor datasets—we found that eDNA from these filters detected only a fraction of the observed and expected fish diversity for these sites. Our results indicate that these discarded filters may not be sufficient for eDNA sampling of fish communities and posit that alternative filter types more appropriate for eDNA sampling may yield more valuable biomonitoring data. Nevertheless, we tested the efficacy of two novel approaches to facilitate large-scale biomonitoring. Though these filters did not yield adequate fish eDNA, the AGAP database provides a useful method for ground truthing fish species presence. The potential of integrating eDNA sampling into existing monitoring frameworks, which, when paired with more optimal eDNA methods, could be a cost-effective strategy to enhance biodiversity monitoring at large scales.