Journal of The World Aquaculture Society最新文献

Striped catfish are one of the main aquaculture species in Asia. However, the low level of omega-3 fatty acids in its body makes this species less attractive compared with marine fish. This study aimed to investigate the effect of different oils on growth performance, body composition, and fatty acids in striped catfish juveniles. A basal diet (T0) was formulated to contain no oil, while four other diets (T1, T2, T3, and T4) were supplemented at 4% with different oils, including salmon oil (SALO), soybean oil (SBO), linseed oil (LSO), and rapeseed oil (RSO). Catfish juveniles with initial body weight (23–24 g/fish) were randomly stocked in 500-L fiberglass tanks, divided into five treatments, three replicates for each, and fed the experimental diets for 60 days. Results from this study revealed that fish fed the LSO-supplemented diet had significantly (p < 0.05) improved whole body omega-3 (alpha-linoleic acid, 18:3n3) fatty acid levels (7.86%), total n-3 fatty acids (9.12%), and higher growth than those fed the other diets. In conclusion, the findings suggest that linseed oil can be used to improve growth, omega-3 fatty acid, C18:3–3 (ALA), and total n-3 PUFA deposition in the whole body of striped catfish juveniles.

Compound plant extracts (CPE) are beneficial for aquatic animals on growth performance and antioxidant capacity. A 56-day experiment was conducted to investigate its positive effect on rice field eel. The fish were fed a commercial diet and supplementing CPE (mainly containing eucommia polysaccharides, reducing sugar) at 0, 0.8, 1.6, 2.4, and 3.2 g/kg. Results showed that dietary CPE significantly increased weight gain and specific growth rate (p < 0.05). Liver lipid content in 1.6 and 3.2 g/kg groups was significantly lower than in 0.8 and 2.4 g/kg groups (p < 0.05). Muscle lipid content in 0.8, 2.4, and 3.2 g/kg CPE groups was significantly lower than in control (p < 0.05). Meanwhile, intestinal digestive enzymatic activities in the 3.2 g/kg CPE group were the highest in comparison to all other groups (p < 0.05). Dietary CPE enhanced the antioxidant activities of serum and intestine (p < 0.05). Compared with the control, intestinal fold thickness in CPE groups was significantly increased (p < 0.05). Furthermore, dietary CPE reduced the degree of liver steatosis and the number of lipid droplet vacuoles. This study indicated that dietary CPE was beneficial to growth performance, antioxidant capacity, liver, and intestinal histology. Supplementation with 1.6–3.2 g/kg CPE is optimal for this eel species.

Promoting the productivity and environmental sustainability of aquaculture is critical in ensuring its healthy development. This study assesses freshwater aquaculture's technical efficiency and ecological efficiency in China's 19 inland provinces from 2008 to 2019, aiming to reveal its productivity and environmental sustainability status. We employ the three-stage Data Envelopment Analysis-CCR (T-DEA-CCR) and three-stage Slack-Based Measure-DEA (T-SBM-DEA) methods to explore the technical efficiency and the ecological efficiency while accounting for environmental conditions and random errors. The average technical efficiency and ecological efficiency during 2008–2019 are 0.857 and 0.702, respectively, indicating substantial scope for enhancing the productivity and environmental sustainability of China's inland aquaculture. We further investigate the regional development using the club convergence, finding that the provincial-level technical efficiencies have already achieved population convergence while the ecological efficiencies diverge into two clubs, suggesting that Chinese freshwater aquaculture's productivity and environmental sustainability have different development pathways. Acknowledging the pivotal roles of environmental protection and growers' training in aquaculture's productivity and environmental sustainability, policymakers may institute funding and recognition to foster the adoption of innovative, environmentally responsible practices by operators.

The present research evaluates the performance of the Nile tilapia (Oreochromis niloticus) (initial weight 11.5 ± 0.07 g) with biofloc technology. For this purpose, spent grains (malted barley) from the brewing industry after aerobic fermentation were used, as both a carbon source (suspended solids) and partial substitute for the diets at 0, 10, 20, 30, and 40% levels (settleable solids). The partial 20% substitution of the diet did not have significant effects on the biological parameters: final body weight, weight gained, average body weight, specific growth rate, daily growth index, condition factor, feed conversion ratio, protein efficiency rate, and viscerosomatic and hepatosomatic indices. However, the dietary substitution showed a significant effect on the final biofloc chemical composition. Nitrogen compounds, NH₄⁺, NO₂⁻, and NO₃⁻, were adequate for tilapia cultivation in all the treatments. No clear effect of partial dietary substitution was observed on meat quality parameters: pH, color, water holding capacity, and amino acid and fatty acid profile of fillet. The results suggest that a 20% substitution of the diet for malted barley is suitable for satisfactory biological parameters and Nile tilapia fillet quality.

Since the early 2000s, aquaculture in Nigeria has grown exponentially. African catfish aquaculture was a major contributor to this expansion. However, a fall in output started in 2015, mostly due to challenging economic conditions which affected farmer's profitability. This challenge has been exacerbated by the COVID-19 pandemic. Notwithstanding, some catfish farms remained profitable. This study investigates the profitability strategies that aid farmers' resilience in times of both economic distress and COVID-type shock. Data from 609 randomly sampled farms across the country were verified and included in the study covering 1118 operations for the pre-COVID and COVID periods. Budgetary analysis was done, and stepwise regression was used to identify factors that most contribute to profitability. These factors were ranked by average profit per kilogram and grouped. The profitability during the periods was influenced by factors within the subcategories of scale of operation, experience, targeted markets, ownership, and pond type. Engagement in other agricultural ventures favored profitability during the COVID period. Profitable and non-profitable groups were further characterized based on their technical and financial indicators. Explored strategies for profitability, including the operation scale, marketing tactics, cost-cutting, and innovative production techniques all proved successful during economic distress and the pandemic.

In Madagascar, fish farming is a complementary activity to agriculture, developed mainly in the highlands region. The common carp, Cyprinus carpio L., is the main species farmed. The availability of fingerlings is one of the key constraints facing the sector. The present study shows the benefit of an appropriate feed and feeding regime to both broodfish and larvae/fry and also the positive impact of protecting larvae during the first stages of their life by using happa system. The combination of these technical approaches increases significantly carp fry production.

β-Catenin (CTNNB) is a core downstream mediator in the Wnt/β-catenin signaling pathway, which plays a role in immune regulation and cell differentiation. In the present study, two CTNNB genes were identified by genomic analysis of Hippocampus erectus and named He-CTNNB1 and He-CTNNB2. He-CTNNB1 was more conserved than He-CTNNB2. The full length of He-CTNNB1 was 2369 bp, including an open reading frame of 2275 bp that encoded 737 amino acids containing 12 armadillo repeats. Phylogenetic analysis revealed that He-CTNNB1 clusters had homologs in other bony fishes. Tissue distribution analysis showed the highest mRNA expression of He-CTNNB1 in the ovary, liver, and kidney of the lined seahorse under normal physiological conditions. The transcription level of He-CTNNB1 was significantly increased in the liver and kidney in response to LPS, poly I:C, and Edwardsiella tarda challenge (p < 0.05). In vitro overexpression of He-CTNNB1 significantly upregulated the expression of key genes of the canonical Wnt/β-catenin signaling pathway, such as axin2, cMyc, and cyclinD (p < 0.05), which increased cell proliferation during the wound-healing process. Taken together, our results suggest that He-CTNNB1 is essential for cell proliferation and the innate immune response in H. erectus.

This study describes the effects on the skeletal phenotype of two pivotal factors, density and water volume, don the hatchery (larval) phase of gilthead seabream (Sparus aurata) larvae previoulsy described for two model species (Danio rerio and Oryzias latipes) and sub-adult (pre-ongrowing) gilthead seabream (Sparus aurata). The experimental trial was conducted using single conditions in a pilot study, starting with a total of 615,385 eggs from the same batch. Three densities (LD low density: 25 larvae/L; MD medium density: 125 larvae/L; and HD high density: 250 larvae/L) and two water volumes (500 and 1000 L) were tested from spawning up to 60 days post-hatching (dph) (average standard length: 1.79 cm; average dry weight: 27.11 mg). On the final samples, morphometric, anatomical, and histological data were collected for data pertinent to meristic counts and skeletal anomalies. The results (analyzed by means of multivariate analyses) indicated that the LD-reared larvae were significantly longer and heavier than HD-reared fish. Furthermore, LD-reared gilthead seabream exhibited a significant reduction in the frequency of individuals with anomalies of jaws, vertebral body shape, and vertebral arches than the MD and HD conditions, which is in agreement with previous experiments carried out on model species and gilthead seabream sub-adults.

This trial aimed to customize pikeperch (Sander lucioperca) larval nutrition using live feed enrichments based on Chlorella vulgaris and Trachydiscus minutus. Pikeperch larvae were fed with rotifers and Artemia enriched with C. vulgaris and T. minutus during the first 17 days after exogenous feeding (started 4 days post-hatching [dph]) and only Artemia until 20 dph. Larvae were exposed to seven different enrichments: (a) Nannochloropsis occulata (Nanno 3600 reed Mariculture) (Control), (b) C. vulgaris cultured at 20°C in BG-117 medium (BG20), (c) C. vulgaris cultured at 30°C in BG-117 medium (BG30), (d) T. minutus cultured at 15°C (T15), (e) T. minutus cultured at 25°C (T25), (f) C. vulgaris cultured at 20°C in urea medium (U20), and (g) C. vulgaris cultured at 30°C in urea medium (U30). After 20 days, no significant differences were found between treatments on total length, standard length, myomere height, and eye diameter. On the contrary, significant differences were found in larval fatty acid composition after the trial period. Larvae from the BG30 treatment showed a significantly higher concentration of docosahexaenoic acid (5.61%), and larvae from the T25 treatment had a higher concentration of eicosapentaenoic acid 12.95%. Furthermore, larvae from the U20 treatment had a significantly higher arachidonic acid concentration of 0.116%. Overall, regarding essential fatty acid concentration, a significant difference was observed between the control treatment (Nannochloropsis) and the other treatments. No adverse effects were found on growth or survival when Nannochloropsis-enriched live feed was replaced with the other enrichments. This trial's results will help optimize the pikeperch larvae's nutritional requirements and diversify the live feed enrichments used during the first feeding.

The live transport of farmed fish is an important practice in Chinese aquaculture due to consumer preferences in its domestic market. However, live transport can be stressful for fish and may cause many welfare issues. This study aimed to examine the effects of transport density on the welfare of largemouth bass (Micropterus salmoides). Adult fish were allocated to four experimental treatments in a two-factor design (N = 5 groups per treatment). Factor one was stocking density of either 39 (low density) or 78 (high density) g L⁻¹. Factor two was transport, with half of the fish groups exposed to simulated transport stress for 3 h using a motion platform, and the other half kept in static tanks for the same length of time. Baseline behavior and physiology were determined from a subset of fish after acclimation but before selection into groups and application of transport. To determine the effects of transport, stocking density, and their interaction on the experimental groups, physiological sampling and behavioral recording were carried out immediately after simulated transport, and water quality was measured both before and after transport. Changes in water quality were observed between two timepoints, with decreased dissolved oxygen levels and increased water temperature. Total ammonia nitrogen levels significantly increased in all treatments over time, particularly in the high-density groups. Fish ventilation rates were significantly elevated in the groups kept at a high stocking density regardless of whether they also experienced transport stress. Fish transported at a high stocking density also showed more fear-related behaviors such as freezing and thigmotaxis than non-transported groups. Serum cortisol, catalase, and aspartate transaminase levels were significantly higher in the transported treatment groups compared to the baseline fish, but no difference was found for serum glucose, lactate, and glutathione peroxidase. We concluded that 3 h of simulated transport was stressful to largemouth bass kept at 78 g L⁻¹, as evidenced by altered fish physiological and behavioral indicators of stress, as well as deteriorated water quality. Additionally, we identified a positive correlation between serum and skin mucus samples for cortisol, glucose, and lactate in transported fish, providing important information for developing less invasive methods for the welfare assessment of largemouth bass.