Aquaculture, Fish and Fisheries最新文献

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.

Integrated fish farming systems are gaining recognition in Ethiopia as a sustainable way to boost productivity, income and food security. However, there is a noticeable lack of scientific analysis regarding the operations and conditions of these systems in the country. This review dives into the various types and components of integrated fish farming, examining aspects like productivity, yield benefits, profitability, economic value, resource efficiency, environmental advantages and challenges, and limitations faced in Ethiopia. We gathered information from a range of sources, including databases like PubMed, Web of Science, Scopus, Google Scholar, as well as documents from the FAO, WorldFish and Ethiopian agricultural research institutes reports. To assess the feasibility of integrated fish farming for optimizing resources, enhancing soil fertility through fishpond effluent and boosting agricultural output and rural livelihoods, we reviewed 90 articles published between 2010 and 2025. The findings indicate that the most commonly used models in integrated systems include fish–vegetable, fish–rice and fish–livestock integrations, candidate fish species like Nile tilapia, African catfish and common carp. Yet, several challenges hinder widespread adoption, such as a lack of technical expertise, limited access to quality inputs, water management issues and legislative gaps. To overcome these challenges, a collaborative effort is essential to build capacity, improve infrastructure and establish market connections. In summary, integrated fish farming system has the potential to transform smallholder farmers in Ethiopia into sustainable food producers, generating income, while also contributing to climate resilience, sustainable aquaculture production and poverty alleviation in the country.

With the rising cost and ecological impact of traditional fishmeal, there is an urgent need for sustainable and locally available alternative protein sources in aquaculture. This study evaluated the effectiveness of Eisenia fetida meal as a sustainable protein substitute for fishmeal in the diets of Oreochromis niloticus fingerlings under controlled conditions. A 90-day feeding trial tested diets with 0%, 25%, 50%, 75%, and 100% fishmeal replacement. Growth performance, feed utilization, survival rate, and production cost were assessed. Partial replacement at 50% and 75% significantly improved final body weight, daily and specific growth rates, and feed conversion ratios (FCR) compared to the control. The 75% replacement diet achieved the best balance between biological performance and economic benefit, reducing production costs by up to 24.7 ETB/kg while maintaining high survival (82.22%) and growth outcomes. Complete replacement (100%) reduced costs further but compromised growth. The study confirms that Eisenia fetida meal, when properly processed, offers a viable alternative to fishmeal for intensive aquaculture operations, with the potential to improve sustainability and profitability.