Aquaculture, Fish and Fisheries最新文献

Recirculating aquaculture system (RAS) is a promising strategy for economically and environmentally sustainable fish farming. Unfortunately, microorganisms in an RAS may produce off-flavours that accumulate in fish flesh and reduce consumer attraction for aquaculture-produced fish. Traditionally, geosmin (GSM) and 2-methylisoborneol (MIB), the compounds causing musty and earthy flavour, have been the most studied off-flavour compounds, but lately other compounds have also been considered important subjects of study. So far, only a little is known about the formation of different compounds at an RAS farm and their concentrations’ fluctuations during the seasons. This case study aimed at monitoring the changes in off-flavour concentrations in different locations of a full-scale (1 M kg a⁻¹) RAS farm rearing rainbow trout (Oncorhynchus mykiss). Off-flavours were measured in fish, in recirculating water and in the inlet water throughout a year. Some of the compounds were introduced to the RAS via inlet water, whereas others were formed at the farm, mostly ranging from 0 to 30 ng L⁻¹. The concentrations of GSM and MIB were below 20 ng L⁻¹ and in most cases below 10 ng L⁻¹, whereas methional peaked up to 70 ng L⁻¹ in the fall and winter. In fish, the concentrations mainly remained below 600 ng kg⁻¹ but occasionally MIB peaked up to 1900 ng kg⁻¹. The results highlight the need for sufficient treatment of inlet water even in the winter to maintain suitable conditions to produce fish of high quality.

The poor retention of mussel spat during the early stages of longline aquaculture is a global issue, leading to inefficient use of juveniles and reduced production yields. In New Zealand, the Greenshell mussel (Perna canaliculus) industry relies heavily on wild-sourced spat, often seeded onto grow ropes in poor nutritional condition, contributing to substantial losses of mussels in the early-stage of production. This study tested whether short-term immersion in sucrose-enriched seawater immediately prior to seeding could improve spat condition and enhance retention and growth, as previous laboratory studies have shown mussel spat can rapidly take up dissolved sugars. Wild spat harvested from Ninety Mile Beach that were in poor nutritional condition were transported to a farm site in the Firth of Thames and immersed for 4 h in one of three treatments: (1) No immersion (control), (2) filtered seawater or (3) filtered seawater with dissolved sucrose (1 mg mL⁻¹). Spat were then seeded directly onto grow ropes on a coastal longline farm. After 85 days, spat densities declined from ∼359,000 m⁻¹ to just 543 m⁻¹ across all treatments, a >99% loss. Immersion of spat in dissolved sugar for 4 h prior to seeding out did not significantly improve the subsequent retention, growth or nutritional condition of the spat. These findings demonstrate that a single 4-h immersion in sugar-enriched seawater was insufficient to improve outcomes on farms. More effective approaches, such as extended nursery periods and better control over seeding densities are needed to improve production efficiency and address the broader challenge of high early-stage losses in global mussel aquaculture.

Green-lipped mussels (Perna canaliculus), like other reef building bivalves, are ecosystem engineers that hold considerable importance commercially and culturally. However, natural beds of this endemic species in Aotearoa New Zealand have been decimated through overharvesting and recovery has been almost non-existent. For restoration purposes, mussels are typically sourced from subtidal aquaculture farms requiring time to allow for successful attachment. This is particularly challenging in exposed environments where dislodgement risk is high and limited research exists. The aim of this field experiment was to investigate the use of cages for different durations to protect and contain adult mussels translocated to a semi-exposed intertidal site to assess attachment success and survival. Farm-supplied mussels (n = 20 per plot) were translocated to plots with no cages, partial cages or full cages for three different durations (i.e., 2, 15 or 29 days; n = 3 plots per treatment). All plots were assessed at 2- and 14-days post cage removal (total experimental period of 46 days). Condition of mussels was also assessed at the start and end of the experiment. The duration of cage containment was shown to be a key factor in attachment success and survival. Results indicated that the longest protection period significantly improved mussel attachment, thereby improving settlement success. A protection period of only two days resulted in ∼98% loss of mussels after 14 days, whereas 29 days of cage protection reduced losses to ∼10%. The condition of mussels at the end of the experiment, however, was reduced compared to deployment. These findings highlight the promising value of using temporary protection during the initial attachment phase of translocated adult mussels and the importance of allowing for an adequate window of opportunity to establish strong byssal attachments to the available substrates. This study provides important insights for future restoration of mussels in semi-exposed intertidal environments.

Maize gluten meal (MGM) can be considered unbalanced in its amino acid profile when used as a fishmeal replacement in aquafeeds. To address this, the present study evaluated MGM as the primary dietary protein source at two inclusion levels in common carp (Cyprinus carpio), with supplementation of crystalline essential amino acids (EAA). Six iso-nitrogenous (40% crude protein) and iso-lipidic (12% crude lipid) diets were formulated based on a basal control diet (Diet1: CTRL). One of these diets was produced in which MGM replaced dietary crude protein at 50% (Diet 2: MGM-50) without EAA supplementation. The third diet was formulated at 75% MGM substitution level and supplemented with l-methionine and l-threonine to meet known requirements (Diet 3: MGM-75). Compounding on the l-methionine and l-threonine inclusion, supplemental l-lysine was included to produce the fourth diet (Diet 4: MGM-75+lys.r). The final two diets contained the same multiple EAA supplementation as the previous diet, but with lysine content doubled to meet the CTRL level (Diet 5: MGM-75+lys.RD) and with additional l-arginine to counteract potential lysine-arginine interactions (Diet 6: MGM-75+lys.RD arg.). Post-feeding trial of nine weeks showed that the optimal growth performance, in terms of weight gain, feed utilisation efficiency and apparent net protein utilisation, was achieved in the CTRL group (SGR 3.01% day⁻¹ and weight gain of 178.17%), followed by MGM-50 (SGR of 2.65% day⁻¹; weight gain of 166.5%). Among all EAAs dietary supplementation, the addition of all EAAs produced the highest weight gain (134.82%, MGM-75+lys.RD arg.). Using life cycle assessment techniques, the feed formulation with the lowest impact was MGM-75. Although fish performance was assessed, MGM-75 had the highest environmental burden due to its high food conversion ratio, resulting in CTRL and MGM-75+lys.RD.arg diets having the lowest environmental impact.

In many countries, foods from aquatic sources provide an important source of protein and key micronutrients. However, aquatic food systems can be impacted by hazards, which drive inefficiencies. Such inefficiencies have consequences for the environmental, economic and social sustainability of food. When directing hazard management resources, it is critical to understand which components of the food system are of most importance to producers, consumers and other interested parties along the value chain. In this paper, we use South Africa as a case study in characterising the aquatic food system. To do this, we created a framework combining production and consumption statistics from the Food and Agriculture Organisation (FAO) of the United Nations with research from global search engines and an in-country publication database. Using this framework, we found that South Africa's aquatic food system is dominated by pelagic and demersal finfish fisheries, such as those for Southern African anchovy (Engraulis capensis) and Cape hakes (Merluccius spp). Aquaculture in South Africa predominantly consists of non-cephalopod molluscs, freshwater fish and some aquatic plants. Although these groups account for approximately 3% of aquatic production in South Africa, they were the focus of over 60% of research from global search engines. In contrast, research from the in-country database focused on finfish fisheries, which contribute 60 times more production volume compared to aquaculture. Therefore, while statistics from the FAO gave a good first overview of the aquatic food system in South Africa, in-country research was invaluable in gaining a holistic understanding of the food system. When applied across the network of food sectors in a country, the approach outlined here, combining production, consumption and research values, provides a framework for practitioners requiring a nuanced overview of a country's food systems, as well as highlighting investment, knowledge and data gaps to target future research.

This study examines how smallholder fish farmers perceive and respond to the environmental impacts of aquaculture, since their awareness, motivations and attitudes shape adoption of sustainable practices. Surveying 125 Nigerian fish farmers as a case example, the results show high environmental consciousness, with 93.7% recognizing the importance of sustainability. Water pollution, excessive chemical use and resource overexploitation are viewed as the main risks of unsustainable farming. Most farmers (78.6%) adopt one or more practices, particularly wastewater treatment and improved feed management. Adoption intensity varied substantially among regular adopters, with nearly half implementing three environmental practices and approximately one quarter adopting four or more practices. Adoption is motivated by sustainability beliefs, cost savings and market demand. Three farmer types emerge: sustainability-oriented, economically motivated and reputation-conscious. Farmers with broader environmental risk awareness adopt significantly more sustainable practices than those with limited perception (p < 0.001). The number of motivational factors does not influence adoption intensity (F(5, 119) = 0.70, p = 0.629). To promote sustainable fish farming, multi-dimensional support programs that integrate economic incentives with environmental values are most effective.

The Japanese Spanish mackerel, Scomberomorus niphonius, in Korean coastal waters has exhibited a consistent increase in catches since the 1970s, peaking in 2023, driven by fishing effort, climate-induced habitat shifts and biological factors. This study examines its trophic ecology and population dynamics, emphasizing the South Sea as a critical habitat, contributing 90.5% of catches, with a rising East Sea contribution since the 1990s due to warming sea temperatures. Stomach content analysis of 741 individuals confirms fish, particularly anchovy (Engraulis japonicus) and largehead hairtail (Trichiurus japonicus), as dominant prey, highlighting its role as a specialist top predator. Seasonal and size-class analyses reveal dietary plasticity, with ontogenetic shifts towards larger, energy-rich prey like largehead hairtail in autumn. Generalized additive model (GAM) analysis indicates nonlinear relationships between mackerel catches and prey availability, with anchovy exerting a positive bottom-up effect. The species’ reliance on key prey underscores its vulnerability to environmental fluctuations and overfishing pressures. Recommendations include climate impact assessments, stable isotope analysis, multispecies modelling and regional migration studies to support ecosystem-based fisheries management for sustainable Japanese Spanish mackerel populations.

Land-based nursery culture for bivalves offers an opportunity to improve the efficiency of bivalve aquaculture because seeding larger and nutritionally healthy juveniles reduces losses during the initial grow-out stages. However, a major problem in establishing nursery culture for bivalves is the reliance on live microalgal food, which is labour-intensive and expensive to prepare. In New Zealand, aquaculture is dominated by the Greenshell mussel (Perna canaliculus), yet little is known about the ability of these juvenile mussels to utilise dissolved amino acids as an alternative nutrient source. Providing dissolved nutrients as a substitute or supplement to live microalgae may be a viable approach to reducing feeding costs. The aim of this study was to determine whether juvenile Greenshell mussels (2 mm shell length) can absorb dissolved amino acids at rates sufficient to contribute to their nutrition in nursery culture. Uptake of glycine, d-asparagine and S-methyl-l-cysteine (1.0 mg mL⁻¹ in seawater) was measured over 4 h. Mussels absorbed each of the three dissolved amino acids at different but constant rates over the 4 h, likely reflecting differences in transporter affinity, that is, glycine and S-methyl-l-cysteine 7.9 mg g⁻¹ AFDW h⁻¹ < d-asparagine 2.6 mg g⁻¹ AFDW h⁻¹. These findings demonstrate that juvenile Greenshell mussels can uptake dissolved amino acids in quantities that are sufficient to provide a useful contribution to their nutrition, confirming their potential as a cost-effective alternative in land-based nurseries compared to wholly relying on feeding live microalgae.

Reproductive migration in anadromous fish involves complex physiological adjustments to support intense metabolic and reproductive demands. In the case of Alosa immaculata, a key migratory species of the lower Danube River, these adaptations can be assessed through hematological and biochemical indicators. During the 2025 spawning season, Pontic shad individuals were sampled in the Chiscani–Galați sector and evaluated for biometric characteristics, sex ratio and physiological status. The results showed a predominance of mature females, with mean individual body weight of 0.21 ± 0.04 kg and total length of 29.72 ± 1.66 cm. Haematological analysis revealed elevated haematocrit (44.13% ± 5.35%) and haemoglobin concentrations (15.75 ± 2.73 g/dL), especially in females at advanced reproductive stages. RBC count and erythrocyte indices (MCV, MCH, MCHC) reflected physiological adjustments to the energetic demands of migration and gonadal maturation. Biochemical profiles indicated adequate nutritional and immune status, with balanced protein values and mineral levels supporting reproductive readiness. Statistical correlations between haematological and biochemical parameters suggested coordinated physiological responses during the reproductive phase. These findings demonstrate that haematological profiling provides a valuable tool for assessing the physiological and adaptive status of A. immaculata during migration and supports its relevance for ecological monitoring and conservation strategies.

Freshwater loaches of the genus Cobitis are small benthic fish inhabiting fine sediments in slow-flowing rivers and vegetated lakes. Due to their small size, low economic value and inconspicuous behaviour, they are rarely studied, and their taxonomy and distribution remain poorly understood. In Switzerland, two species are considered native: Cobitis taenia north of the Alps and Cobitis bilineata in the southern Po basin. Historically, all loaches north of the Alps were attributed to C. taenia, and those to the south to C. bilineata. However, due to their morphological similarity, misidentifications have been common, and the true distribution of each species remains uncertain. Recent studies using morphological and environmental DNA (eDNA) methods have detected only C. bilineata north of the Alps, suggesting that C. taenia may never have been present in this region or has since disappeared. However, the existence of relict populations cannot be entirely ruled out. In this study, 35 rivers in western Switzerland (cantons of Vaud, Fribourg, Geneva and Neuchâtel) were surveyed using high-volume eDNA filtration (up to 60 L per sample). C. bilineata was detected in 10 of the 35 watercourses—2 in the Rhône basin and 8 in the Rhine basin—whereas no C. taenia was found. These results support the hypothesis that C. taenia is absent or extinct in western Switzerland. A parallel museum survey also confirmed that specimens collected as early as 1962 could be attributed to C. bilineata on the basis of morphology. This study confirms the effectiveness of high-volume eDNA sampling in detecting cryptic species such as C. bilineata.