Aquaculture, Fish and Fisheries最新文献

Fish growth can be highly variable among populations of the same species due to differences in abundance, system productivity and watershed characteristics. Because of this, understanding factors that influence fish growth and body condition is important to managers for fish conservation, to meet angler desires and to support local economies. As ecosystems respond to a changing climate, species compositions can change. In north temperate lakes, this is often exemplified by an increase in largemouth bass (LMB). These lakes are often managed for multiple fish species concurrently, making standardized fishery-independent LMB data limited, creating challenges for managing this species. As such, a better understanding of factors influencing LMB body condition and growth may become critically important in the future. We assessed LMB age, length, and weight data to test for abiotic and biotic lake characteristics explaining variation in LMB body condition, asymptotic length, and mean length at age metrics in Wisconsin from 1994 to 2022. Macrophyte species composition and lake classification relationships were the two primary predictors of variation in LMB growth. Lakes with degraded macrophyte communities were associated with larger individual LMB sizes as were lake class types that contained cool water and riverine characteristics. Our results provide fisheries managers with options when dealing with diverse angler desires and a heterogenous landscape of lakes. Where available, macrophyte species composition data can be consulted by managers to identify opportunities to provide a trophy fishing experience in a system that otherwise would be undervalued. As populations of LMB increase in Wisconsin lakes, a better understanding of how to effectively reach goals set by managers, and what realistic goals might be, is required, and understanding what lake characteristics can explain variation of body condition gives insight to that end.

The pearling industry is one of Australia's most valuable and iconic industries, creating significant economic and employment opportunities across Northern Australia. To improve our understanding of the relationship between the silver-lipped pearl oyster and its biotic and abiotic environment using transcriptomics, oyster spat are collected weekly from several offshore sites in Northwestern Australia. However, due to the remoteness of the farming locations, collected spat must be transported on ice for intervals before snap-freezing becomes possible. In this study, we investigate the impact of incubation on ice for intervals of up to 90 min on the global gene expression of collected spat. Preserving spat on ice for up to 90 min did not significantly impact the RNA concentration or quality. On average, more than 100 ng/µL of RNA (RIN 7.0–8.5) was extracted per sample to generate sequencing libraries, and no significant impact on sequencing and mapping reads to the genome was observed between treatments. However, prolonged incubation on ice did alter gene expression, with a significant increase in differential gene expression observed after 60 min. Furthermore, changes in the number of predicted genes, potentially in response to stress and cold, including stress-related heat shock protein (HSP) and Cytochrome P450 (CYP) genes, immune-related perlucin-like genes, and solute carrier (SLC) transporters, were observed with prolonged incubation. The observed stress-induced changes can alter the global gene expression status of the spat at the time of collection and may lead to misinterpretations upon analysing the impact of abiotic and biotic factors on the health of silver-lipped pearl oyster spat. Prolonged incubation intervals of oyster spat on ice destined for RNASeq analysis are therefore not recommended. Remote sites for longitudinal and comparative studies were therefore selected with this guideline in mind. This study also demonstrates the importance of conducting pilot trials in the development of research study protocols.

This study aimed to determine the optimal inclusion level of a protease in the diets of Nile tilapia (Oreochromis niloticus) to enhance growth performance, nutrient utilization and fillet quality. Two experiments were made, one to determine the optimal level and a second experiment to validate these levels of supplementation in diets of tilapias. The first experiment consisted of six treatments, each with six replicates, and 25 fish per experimental unit. The treatments were as follows: crescent levels from 0, 25, 50, 75, 100 and 125 g/t of protease. In the second experiment, the treatments were as follows: (1) Positive Control (PC), meeting all nutritional requirements; (2) Negative Control 50 (CN50), with a 50% reduction based on the Precizyon PRO 50 matrix; (3) Negative Control 100 (CN100), with a 100% reduction; (4) Negative Control 150 (CN150), with a 150% reduction; (5) CN150 supplemented with 50 g/t of Precizyon PRO 50 and (6) CN150 supplemented with 75 g/t of Precizyon PRO 50. After analysing the results, it was observed that the addition of Precizyon PRO 50 to Nile tilapia diets significantly enhanced nutrient digestibility, growth, intestinal structure and fillet quality. Optimal levels of Precizyon PRO 50 were found to be between 71 and 77 g/t. Supplementing diets with 50–75 g/t of Precizyon PRO 50 effectively mitigated performance deficits caused by reduced amino acid levels, thereby improving growth, fillet yields and overall health.

Mariculture holds significant promise for enhancing food security, blue economy development and climate-resilient livelihoods along Kenya's 640 km coastline. This review synthesises over two decades of empirical and grey literature to examine the current status, production trends, challenges and future prospects of commercially cultured mariculture species in Kenya. The review focuses on key species including milkfish (Chanos chanos), rabbitfish (Siganus sutor), seaweed (Eucheuma spp.), mud crab (Scylla serrata), prawns (Penaeus spp.), oysters (Saccostrea cucullata), Artemia franciscana and sea cucumbers (Holothuria scabra). Despite a favourable marine environment and policy recognition, the sector remains underdeveloped, with total production in 2023 reaching only 112 metric tons. Major constraints include limited hatchery capacity, weak technical knowledge, policy and regulatory fragmentation, infrastructural gaps and fragile market linkages. Nonetheless, emerging opportunities are evident: seaweed farming has shown rapid expansion with high female participation; integrated multi-trophic aquaculture (IMTA) offers ecological and economic efficiencies; and strategic investments such as the National Mariculture Resource and Training (NAMARET) Center promise to improve seed and training access. The review identifies the potential for upscaling finfish and shellfish farming, diversifying species portfolios and strengthening mariculture value chains through policy alignment, climate adaptation and blue economy integration. Addressing key constraints through targeted investment, inclusive community participation, and sustainable technologies will be critical to unlocking the sector's growth. This synthesis provides a foundation for policymakers, researchers and stakeholders to develop resilient, inclusive and market-oriented mariculture systems in coastal Kenya.

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.