Aquaculture Research最新文献

This study assessed the influence of salinity and element composition of rearing seawater on unfed Japanese eel (Anguilla japonica) larvae at 5 days after hatching (DAH). First, no significant differences in larval survival were found between natural and artificial seawater across various container materials and sizes (50mL–20 L). Subsequently, 10 to 15 larvae were housed in 100m L polypropylene (PP) bottles with seawater of different elemental compositions. Analyses of mean lethal DAH, survival activity index (SAI), and survival rate on the mean lethal DAH demonstrated that Na, Mg, K, and Ca are essential, while S and Cl also appear highly required. Next, optimal salinity (1–34 psu) was investigated by rearing individual larvae in 48-well microplates, revealing that SAI peaked at 13–16 psu. Formulated seawater containing these six key elements at 13 psu significantly enhanced larval survival. These findings confirm that specific salinity and elemental composition are conducive to Japanese eel larval survival and offer insights for optimizing hatchery protocols.

Limited information is available about the digestive tract morphology and function in some marine fish species. Using anatomical methods, this study compared the morphological characteristics of the digestive tract among 11 marine fish species of different taxonomic status, feeding habits and ecological niches. Except for black scraper (Thamnacomus modestus), a omnivores fish, the rest of fish species involved in this study, are carnivorous fish. Three replicate fish of each species were used. The relative intestine length (RIL) of black scraper (T. modestus) was the highest among all species investigated, while skate (Raja kenojei) had the lowest RIL. The hepatosomatic index (HSI) was the highest in tiger puffer (Takifugu rubripes) and the lowest in Japanese Spanish mackerel (Scomberomorus niphonius). The highest viscerosomatic index (VSI) was found in black scraper and the lowest value was found in Japanese Spanish mackerel. In terms of stomach morphology, black scraper, tiger puffer, turbot (Scophthalmus maximus), javelin goby (Synechogobius hasta) and skate had ‘I’-shaped stomach; greenling (Hexagrammos otakii), rockfish (Sebastes schlegelii) and hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) had ‘V’-shaped stomach; while Japanese Spanish mackerel, Chinese seabass (Lateolabrax maculatus) and conger eel (Conger myriaster) had ‘Y’-shaped stomach. Besides, the pyloric caeca were found in turbot (S. maximus), greenling (H. otakii), rockfish (S. schlegelii), hybrid grouper (E. fuscoguttatus♀ × E. lanceolatus♂), Japanese Spanish mackerel (S. niphonius) and Chinese seabass (L. maculatus). The oropharyngeal morphology of fish provided clues to fish feeding pattern. In conclusion, for the 11 marine fish species, the morphological structure of stomach and oropharyngeal cavity, and the RIL had high correlation with their body shape, oropharyngeal capacity and feeding habit.

Rhodobacteraceae strains are known to play multiple beneficial roles in shrimp aquaculture. Roseovarius litoreus (RL), a member of this family, has demonstrated probiotic effects in crabs. To explore its potential role in shrimp, this study evaluated the effects of RL on the growth performance, antioxidation, and gut bacterial community of the postlarvae of shrimp Litopenaeus vannamei in an 8-week immersion supplementation experiment. The results revealed that RL significantly increased the weight gain rate (WGR, p < 0.0001) and specific growth rate (SGR, p < 0.0001) while suppressing the mRNA expression of muscle MSTN (p < 0.001), a gene involved in muscle growth regulation. Although RL did not markedly affect superoxide dismutase (SOD) activity, total antioxidant capacity (T-AOC), or malondialdehyde (MAD) levels, it significantly enhanced catalase (CAT) activity. Additionally, RL modulated the gut bacterial community, notably reducing zero-radius operational taxonomic unit (ZOTU) richness and enriching beneficial genera such as Lysobacter, Bacillus, and Ruegeria. Functional profiling indicated that these enriched ZOTUs were associated with enhanced development and regeneration, digestive system function, and immune responses. In summary, this study suggests that RL holds promise as a probiotic candidate for shrimp aquaculture.

Growth hormone (GH)-releasing peptides (GHRPs) regulate growth and immune responses in fish, offering potential aquaculture applications. This study evaluated the effects of GHRP-6 and its recombinant analog, F5WAC (acetylation of the N-terminal Histidine [His1] and substitution of D-Phenylalanine with D-Tryptophan at position 5), on growth performance, immune function, and metabolic parameters in common carp fry (Cyprinus carpio). Peptides (GHRP-6 and F5WAC) were administered at 100 μg/kg feed over 4 weeks. F5WAC significantly elevated GH levels, cortisol, and immune markers (IgM, C3, and lysozyme activity), alongside upregulated igf1 gene expression, compared to GHRP-6 and controls. Furthermore, F5WAC-treated fry exhibited superior weight gain, feed conversion ratio (FCR), and specific growth rate (SGR). These results position F5WAC as a potent growth and immune enhancer, with promising applications in sustainable aquaculture practices.

Mystus cavasius (locally known as Gulsha) is a commercially important catfish in Bangladesh, typically transported live in oxygenated polythene bags without anesthetics, often resulting in severe stress, injuries, and high mortality. This study evaluated the efficacy of clove seed aqueous extract (CAE) as a natural anesthetic at different concentrations to establish a standardized anesthetic protocol for minimizing transport-related stress. Fish (15.14 ± 1.75 cm; 24.80 ± 1.50 g) were exposed to CAE across three experimental phases: (1) determination of effective concentrations (30–100 mg/L) based on induction and recovery times; (2) evaluation of opercular rate, water quality, and physiological stress indicators in oxygenated bags; (3) assessment of stress responses under varying packing densities using the optimal concentration. Results indicated that sedation was initiated between 40–55 mg/L CAE, with 55 mg/L identified as the most effective concentration for 9–12 h of transport. At this concentration, fish exhibited significantly reduced total ammonia nitrogen (TAN), blood glucose, and leukocyte counts, while maintaining 100% survival and minimal stress even under high-density conditions. These findings demonstrate that CAE is an effective, natural, and locally available anesthetic for M. cavasius, leaving no harmful residues and ensuring safe and high-quality live fish for consumers.

Crustacean shells are composed of chitin, which is bound to protein and minerals, along with other essential nutrients. These components are necessary for growth, immune response, the formation of reproductive structures, and the enhancement of sperm quality. This study aimed to evaluate the effects of prawn shell meal diets on hemocyte count, hemolymph clotting, and sperm quality of the freshwater prawn Macrobrachium caementarius. The prawns were distributed into three dietary treatments, consisting of a basal diet (control) and two experimental diets supplemented with 20% raw prawn shell meal (RPSM) and 20% cooked prawn shell meal (CPSM). Hemocytes were counted, and the hemolymph clotting time was determined. Spermatozoa in spermatophores and the vas deferens were counted. Sperm quality was assessed by staining. The RPSM and CPSM diets did not lead to an increase in hemocytes, nor did they affect the clotting time of the hemolymph. However, with the RPSM diet, there was an increase in the number of normal spermatozoa in the entire vas deferens (from 3.65–8.11 × 10⁵ spz/mL) and a lower proportion of dead and abnormal spermatozoa (<2 × 10⁵ spz/mL). These findings suggest the potential of RPSM and CPSM diets to improve sperm quality in the freshwater prawn. Further research based on isoproteic and isolipidic diets should be performed to ascertain whether RPSM could increase reproductive performance in male individuals of the freshwater prawn.

Red tides sometimes impact the aquaculture industry worldwide, resulting in mass fish mortalities. It is known empirically that their effects can be mitigated by cessation of feeding. However, specific methods to maximize this technique’s effectiveness and provide physiological support remain limited. In the present study, we investigated the effects of the feeding-cessation period on a fish’s resistance to a harmful red-tide microalga, the Chattonella marina complex (“Chattonella”), using yellowtail (Seriola quinqueradiata) of two ages and body weights: juveniles (74 days after hatching and ~15 g) and young (201 days after hatching and ~860 g). The fish mortality by Chattonella is thought to be associated with gill damage. Thereby, we measured oxygen consumption to consider plankton contact with the gills. Our results showed that feeding cessation for 4 or more days significantly increased survival, regardless of size. Body weight decreased with longer feeding cessation, but survival rates were not affected by body weight. To test red-tide resistance, juvenile yellowtail were treated by feeding cessation for 1, 2, and 4 days, and young yellowtail for 1, 4, and 8 days. In the juveniles, a longer feeding pause also reduced oxygen consumption. Moreover, histological examination of the juveniles showed that a longer feeding pause reduced damage to the secondary lamellae of the gills. We propose that gill damage was mitigated by reducing the interaction between Chattonella cells and the gill lamellae, likely as a result of decreased oxygen consumption. These results indicate that feeding cessation for a specific period of time physiologically improves red-tide resistance in yellowtail.

Global aquaculture expansion necessitates sustainable technologies like biofloc technology (BFT), and the type of carbon source exerts a crucial impact on the functionality of biofloc systems. This study aimed to evaluate the effects of single carbon sources (glucose [G] and maltodextrin [M]) and their 1:1 mixture (GM) on water quality, microbial communities, growth performance, and physiological status of redclaw crayfish (Cherax quadricarinatus) in BFT systems, with a clear-water group (F) as the control. A 70-day experiment was conducted in triplicate tanks per treatment, with key parameters (water quality indices, microbial diversity via 16S rRNA sequencing, growth metrics, and hepatopancreatic antioxidant enzyme activities) measured. Data were analyzed using one-way ANOVA followed by Tukey’s Honestly Significant Difference (HSD) test (p < 0.05). Key findings showed that the GM group exhibited significantly higher microbial alpha diversity (Shannon index and Simpson index; p < 0.05 vs. all groups) and stronger functional redundancy, enriched with synergistic taxa such as Dechloromonas and Chryseolinea. Compared to the F group, all BFT groups significantly improved production yield (GM: 135.72 g vs. F: 119.35 g; p < 0.05), survival rate (GM: 88.89% vs. F: 70.22%; p < 0.05), and feed conversion ratio (GM: 1.72 vs. F: 1.89; p < 0.05), with GM performing optimally among BFT groups. The GM group also maintained a balanced carbon-to-nitrogen ratio (C:N) and stable total suspended solids (TSS) dynamics, while crayfish in GM showed significantly enhanced superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) and reduced malondialdehyde (MDA) levels (p < 0.05). All biofloc systems demonstrated economic viability (benefit-cost ratios (BCRs) > 1.40). This research provides a practical microbial-based strategy for improving redclaw crayfish culture and crustacean aquaculture sustainability via optimized carbon source management in BFT.

Mixed lineage kinase domain-like pseudokinase (MLKL) is a key effector of necroptosis. We identified an MLKL homologue from Hexagrammos otakii, named HoMLKL. The open reading frame (ORF) of HoMLKL contained 1497 nucleotides and encoded a protein with 498 amino acids (Mw = 57.15 kDa). Bioinformatic analysis revealed that HoMLKL is highly conserved. In the experiments, fish were exposed to 16°C (control), 24°C, and 28°C for up to 24 h, and samples were taken at 0, 6, 12, and 24 h. We used quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and immunohistochemistry (IHC) to quantify HoMLKL and related protein in the cardiac tissue of H. otakii. Cardiac injury was evaluated by histopathology and biochemical assays. The results showed that HoMLKL may play an important role in heat-stress-induced cardiac injury in H. otakii. Heat stress significantly upregulated HoMLKL, receptor-interacting protein kinase 1 (RIPK1), and receptor-interacting protein kinase 3 (RIPK3) expression (p < 0.05), indicating activation of the necroptosis pathway. Cardiac damage was characterized by elevated creatine kinase (CK) and lactate dehydrogenase (LDH), myocardial disorganization, vascular congestion, chromatin condensation, and inflammatory cell infiltration. Increased expression of inflammatory factors and reduced glucose levels suggested concomitant inflammation and metabolic dysfunction. These findings demonstrate that HoMLKL likely cooperates with RIPK1/RIPK3 to mediate necroptosis, linking heat stress to cardiac injury and inflammation in H. otakii, and provide insight into stress-induced necroptosis in fish.