Journal of The World Aquaculture Society最新文献

This study investigated the effects of dietary black soldier fly (BSF) larvae, Hermetia illucens, meal on growth performance, feed utilization, intestinal health, and immune response in Nile tilapia, Oreochromis niloticus, juveniles. The fish (initial weight: 7.28 ± 0.09 g) were reared in a recirculatory aquaculture system (RAS) and fed diets containing different levels of defatted BSF larvae meal: 0% (control diet), 20% (BSF20), and 40% (BSF40). At the end of the feeding trial, the final body weight, weight gain, specific growth rate (SGR), protein efficiency ratio (PER), and feed conversion ratio (FCR) were significantly (p < 0.05) improved with increasing BSF meal inclusion levels in the diet. Histological analysis of the intestine revealed that mucosal fold length (MFL), muscularis thickness (MT), and goblet cell density (GCD) were significantly elevated by the BSF meal compared with the control. In addition, intraepithelial lymphocytes (IELs) and the enterocyte microvilli length were significantly elevated in BSF40-fed fish compared with the control. Gene expression analysis showed that intestinal chitin digestion-related (endochitinase A) and amino acid transporter (Slc6a18) genes were not significantly affected by the BSF meal. However, the expression of peptide transporter Slc15a1a was upregulated in the fish fed BSF40 compared to the control. Moreover, posterior intestine and head kidney cytokine (IL-1β, TNF-α, and IL-10) gene expression levels were not significantly affected by the inclusion of the BSF meal. Therefore, these results suggest that the BSF meal up to a 40% inclusion level can be used as an alternative protein source in the diets of Nile tilapia juveniles to promote growth and intestinal health.

The kuruma shrimp (Marsupenaeus japonicus) is a highly fecund marine aquaculture species with substantial variance in reproductive success. These traits may lead to genetic diversity loss and inbreeding, particularly under mass selection programs. In this study, we assessed genetic diversity levels and effective population size across 18 M. japonicus families using 10 microsatellite markers. The results demonstrated that the cultured families of M. japonicus exhibited lower heterozygosity. Pairwise comparisons of genetic differentiation coefficients revealed moderate to high differentiation among the families. Phylogenetic, structural, and discriminant analyses of principal components identified two distinct genetic clusters within the sampled families. Low effective population size estimates and genetic bottleneck signatures were observed, likely due to incomplete or skewed parental contributions to offspring. Therefore, we recommend implementing mating schemes involving genetically distant brooders. These findings provide critical insights for population level genetic studies and breeding strategy optimization in M. japonicus.

The flatfish is a major farmed species consumed globally in large quantities. However, due to the densely populated farming environment, flatfish are susceptible to lesions and diseases, making early lesion detection crucial. Traditionally, lesions were detected through visual inspection, but observing large numbers of fish is challenging. Automated approaches based on deep learning technologies have been widely used to address this problem, but accurate detection remains difficult due to the diversity of the fish and the lack of a fish lesion and disease dataset. This study augments fish lesion images using generative adversarial networks and image harmonization methods. Next, lesion detectors are trained separately for three body parts (head, fins, and body) to address individual lesions properly. Additionally, a flatfish lesion and disease image dataset, called FlatIMG, was created and verified using the proposed methods on the dataset. A flash salmon lesion dataset was also tested to validate the generalizability of the proposed methods. The results achieved 12% higher performance than the baseline framework. This study is the first attempt to create a high-quality flatfish lesion image dataset with detailed annotations and proposes an effective lesion detection framework. Automatic lesion and disease monitoring can be achieved in farming environments using the proposed methods and dataset.

Gracilariaceae species are among the most economically important seaweeds, with a wide range of applications. Large-scale cultivation of Gracilariopsis lemaneiformis has already been established along the eastern coast of China. However, as global demand for Gracilariaceae species rises, it is crucial for China to expand large-scale cultivation of these species to other coastal regions. Although the South China Sea harbors rich macroalgal resources, including Gracilariaceae, large-scale cultivation of these species has yet to be implemented in the region. To identify heat-tolerant Gracilariaceae species suitable for large-scale cultivation in the South China Sea, we conducted surveys between June and August from 2021 to 2024. Several heat-tolerant species were identified. Taxonomic identity was confirmed through detailed morphological examination and molecular analysis of rbcL and cox1 gene sequences. We identified eight species of Gracilariaceae, including one Gracilariopsis (Gp.) species and seven Gracilaria (G.) species. Morphologically, the species were characterized as follows: Gp. heteroclada (long secondary branches with short or spiny tertiary branches), G. salicornia (club-shaped segments), G. vermiculophylla and G. tenuistipitata (slender-branched), G. edulis (broom-like appearance with red-tinged branch bases), G. firma (highly constricted branch bases), and two unclassified species, Gracilaria sp.1 and Gracilaria sp.2. This study contributes to the taxonomic knowledge of Gracilariaceae and provides valuable information for the development of heat-tolerant species suited for large-scale cultivation in the South China Sea.

Microalgae are essential food sources for fish and shellfish aquaculture and contain abundant lipids with diverse fatty acid profiles. Quantification of total lipids in microalgae could assist commercial microalgal culture operations, harvest, and management in hatchery farms. Currently, reported protocols for lipid quantification are mainly for biofuel microalgal species. This study aimed to develop effective methodologies for total lipid quantification in three aquaculture microalgae using lipid-specific probe BODIPY™ 505/515 and flow cytometry. The objectives were to determine the effects of (1) staining concentration and time; (2) microalgal concentration; and (3) microalgal age. For Tisochrysis lutea, Chaetoceros muelleri, and Tetraselmis suecica, the optimal staining concentrations and times were 2.0 μg/mL for 0.5–30 min, 2.5 μg/mL for 5–30 min, and 1.5 μg/mL for 5–30 min, and the suitable algal concentrations were 5 × 10^5–6, 5 × 10^4–6, and 1 × 10^4–6 cells/mL. The total lipid accumulation in all three microalgae was contrary to the cell growth— low at the exponential growth stage and high at the stationary stage (beyond day 9). Overall, the methodologies developed in this study could be used to quantify total lipids in microalgae rapidly and accurately and require a small sample biomass (about 1 mL directly from algal culture). To produce microalgae with high total lipid accumulation, the best time to harvest may be at the stationary stage but not at the exponential growth stage. This study provided a better understanding of the lipid accumulation dynamics in the three aquaculture microalgae.

A by-product of black soldier fly (Hermetia illucens) larvae (BSFL) farming is the chitin-rich “exuviae” (exoskeleton shell) that is left behind after the prepupae larvae metamorphose into adults. Moreover, exuviae is present in BSFL meal and frass. In this 8-week trial, tilapia (initial weight of 2.93 g) were fed diets with increasing inclusions of dietary BSFL exuviae (0%, 0.05%, 0.1%, or 0.5%) and the growth, biochemical composition, hepatic expression set of genes related to metabolism as well as liver/intestinal histomorphology were examined. Growth metrics tended (p = 0.066) to increase linearly with increasing exuviae level, although the feed conversion ratio was unaffected. Muscle P and Zn content were significantly linear and/or quadratic with respect to dietary exuviae level and were highest in fish fed the control diet and lower in fish fed diets with exuviae. Dietary BSFL exuviae at 0.1% and 0.5% significantly downregulated the hepatic expression of lipoprotein lipase, trypsinogen, and cytochrome P450 1A (cyp1a) genes relative to control. Liver histology and scoring revealed mild to severe changes ranging from localized inflammation to necrosis and hemorrhaging with increasing exuviae content, while intestinal histology appeared similar among treatments. Muscle protein and amino acids decreased either linearly or quadratically with increasing BSFL exuviae. Muscle lipid and fatty acid profiles were not significantly impacted by dietary treatments. Results suggest that dietary inclusion of BSFL exuviae up to 0.5% of diet did not limit tilapia performance, but further research is needed on treatments of BSFL meal or exuviae prior to diet inclusion to reduce liver pathologies and potentially enhance fish production.

Pre-slaughter processes impact trout production, but the optimization of pre-harvest crowding in an industry affected by global warming has scarcely been studied. In this study, we evaluated the effect of two crowding methods on the welfare of rainbow trout (Oncorhynchus mykiss) across two seasons (winter and summer). Each season 660 trout were distributed into separate tanks, and two crowding methods were applied: reducing water level (WL) and applying lateral compression (LC) within the tanks. Welfare indicators included plasma metabolites and tissue color, while fillet quality was evaluated based on indicators such as muscle color, muscle pH, and rigor mortis. These parameters were evaluated to determine the impact of each crowding method on both fish welfare and fillet quality. Tests were conducted in winter (8.80 ± 1.79°C) (WI) and summer (22.0 ± 0.06°C) (SU). Cortisol, creatine phosphokinase, and lactate levels in plasma were lower using WL, indicating a reduced stress response, supported by various skin color attributes (a*, b*, C*, and h*), liver (a*, C*, and h*), and fillet (h*). Similarly, muscle acidification (pH) was lower using LC, which could lead to potential texture deterioration. Temperature was a crucial factor globally across all parameters, with better results in WI. The combination of both treatments showed, on one hand, abnormal values of cortisol, glucose, and skin color attributes (a* and C*) and fillet (24 h post-mortem) (b* and C*) in summer LC, and on the other, better muscle pH and fillet color (b* and C*) at 0 h post-mortem using WL in WI. Overall, stress response was lower and fillet quality was better in WL fish. This trend was similar in winter compared to summer trout, regardless of the crowding method. Despite the poorer outcomes from LC, whether due to increased swimming difficulties or worse distribution of dissolved oxygen, its use in summer is discouraged due to cumulative effects, recommending its use only in winter when unavoidable.

Biofouling-induced increases in labor costs are among the most impactful factors determining the technoeconomic feasibility and profitability of aquaculture operations. Understanding how different cultivation methods and environmental conditions influence the severity of biofouling is crucial to support informed decision-making by farmers and minimize the economic impacts of biofouling in the aquaculture industry. This study used a factorial design to compare the extent and type of biofouling across three common cultivation methods (floating bags, floating cages, and bottom-culture) in exposed and sheltered locations that differ in temperature, salinity, turbidity, and wave energy. The ratio of fouling weight to oyster wet weight for oysters grown in floating bags was significantly higher than for oysters grown in floating cages, which were in turn significantly more fouled than bottom-planted oysters. Oysters cultivated in the exposed location had a significantly higher fouling ratio than oysters cultivated in the sheltered location. However, this pattern was driven by the stark difference in fouling by location for the floating bags, indicating that differences in temperature and wave exposure between sites would have the greatest impact on fouling severity for oysters grown in floating bags. Common fouling organisms included solitary and colonial tunicates, filamentous algae, and hard fouling (mussels, oyster spat, and barnacles). The significant differences observed in the composition and severity of oyster biofouling by gear type and growing site underscore the importance of considering fouling potential when evaluating the profitability of a farming strategy and the need for further development of region- and gear-specific biofouling mitigation strategies.

Streptococcus iniae is a fish pathogenic bacterium distributed worldwide. It has a wide range of hosts, strong infectivity, causes high mortality, and severely hinders the healthy development of the aquaculture industry. A fish epidemic broke out in a Selenotoca multifasciata aquaculture farm, Hainan Province, China, and resulted in numerous deaths. Sick fish showed symptoms including erratic swimming, skin darkening with generalized hemorrhages, and internal organ and brain hemorrhages. A dominant strain, SI03, isolated from the brain of a dying S. multifasciata, exhibited high virulence, and was identified as serotype I γ-hemolytic S. iniae. Subsequently, virulence gene mRNA expression, infection kinetics, as well as the histopathology in S. multifasciata infected with SI03 were analyzed. Results showed that the mRNA expression levels of scpI, simA, pdi, pgmA, and cfi genes in γ-hemolytic S. iniae SI03 were significantly higher than those in β-hemolytic S. iniae ATCC 29178. These genes are associated with adhesion, invasion, and immune evasion. While the mRNA expressions of sagA-sagI genes, which are associated with the streptolysin S, were significantly lower than those of β-hemolytic S. iniae ATCC 29178. After being challenged with SI03, the number of bacteria in all the tested fish tissues increased significantly in 24 h. The challenged fish showed symptoms similar to those of the fish from which SI03 was originally isolated. It appears that S. iniae SI03 may have developed a compensatory pathogenic mechanism for hemolysis deficiency. This mechanism enhances its adhesion, invasion, proliferation, and immune evasion abilities. The results of this research provide a reference basis for the prevention and control of S. iniae.

The Potter's angelfish (Centropyge potteri), a Hawaiian endemic reef fish, has long been prized in the global aquarium trade, with approximately 9000 individuals collected annually from the wild before Hawai‘i's 2021 ban on commercial aquarium fish collection. This study marks the first detailed description of aquaculture techniques with replicated results for the species, providing foundational data on larval growth and survival critical for advancing culture techniques for C. potteri and other reef fishes. By iteratively refining feeding protocols, survival rates to settlement improved from 0% to 3.4%, largely by addressing acute mortality points during feed transitions. Egg and larval development closely resembled other Centropyge species, with flexion between 14 and 21 dph, and settlement behaviors observed at ~60 dph. Spawning in captivity followed lunar cycles, with broodstock producing viable eggs nightly from December 2022 to May 2024. Larval rearing trials compared three feeding protocols along with the effects of egg stocking densities and live algae densities. Early development revealed critical vulnerabilities during feed transitions, particularly with newly hatched Artemia and dry feeds, which were mitigated by delayed introductions. Continuous live algae (Tisochrysis lutea) and adult Parvocalanus copepods through settlement were essential for success, while larger tanks (1000 L) improved survival by minimizing environmental stress compared to smaller tanks (200 L). The revised feeding regime supported the highest survival rates with algae densities of 75,000–150,000 cells/mL. The results emphasize the importance of diet composition and timing, environmental stability, and tank management for successful larval rearing. Future research should prioritize pathogenic bacteria control in live feeds and refining feed transitions to further improve aquaculture efficiency. This study aligns with efforts to transition the industry toward sustainable aquaculture practices, reducing pressures on wild populations and supporting reef conservation while offering a scalable model for aquaculture of other high-value reef fish species.