Daphnia carinata is an important biological live feed in aquaculture. Conventionally, D. carinata is cultivated and fed with fresh Chlorella pyrenoidosa, which is inconvenient for storage and transportation. After undergoing vacuum freeze‐drying or spray‐drying, C. pyrenoidosa exhibits advantages such as reduced weight and easier storage and transport. This study investigated the effects of feeding freeze‐dried and spray‐dried Chlorella on the reproductive performance and fatty acid composition of D. carinata. The results indicated that there was no significant difference in reproductive performance between the two groups of D. carinata fed with freeze‐dried Chlorella and fresh Chlorella. However, a significant decline in reproductive performance was observed in the group fed with spray‐dried Chlorella. The contents of crude fat and unsaturated fatty acids in freeze‐dried Chlorella were significantly higher than in spray‐dried Chlorella. Additionally, D. carinata fed with freeze‐dried Chlorella exhibited significantly higher levels of unsaturated fatty acids (especially ALA and EPA) than those fed with spray‐dried Chlorella. In conclusion, freeze‐dried Chlorella can be used as an alternative to fresh Chlorella for cultivating D. carinata. Unsaturated fatty acids are a key factor influencing the reproductive performance of D. carinata.

This study evaluated the effects of different salinities on the growth and physiology of whiteleg shrimp (Litopenaeus vannamei) postlarvae reared in the biofloc system. A total of 4200 shrimps (PL20) were randomly distributed in 12 850 L biofloc (BFT) tanks (350 PL20 in each tank). Shrimps divided into four experimental groups in the biofloc system with salinities of 3 (BFT3), 8 (BFT8), 10 (BFT10), and 12 ppt (BFT12). Salinities were made by adding sea salt to tap water. During the rearing period, for the optimal growth and development of biofloc in the tanks, a carbon source (brown sugar and wheat flour in equal proportions) was calculated and added to the tanks to adjust the ratio of carbon to nitrogen (12:1). From the third to the sixth week of rearing, the water nitrate concentration was significantly higher in BFT12 and BFT10 (p < 0.05). The total ammonia nitrogen and nitrite concentration at different sampling times did not show significant differences among experimental groups (p > 0.05). After 6 weeks, salinity had no effect on the growth indices including final weight, weight gain (WG), WG rate, specific growth rate (SGR), and survival (p > 0.05). The highest levels of intestinal amylase (28.97 ± 3.46 U/mg protein) and protease (13.28 ± 2.19 U/mg protein) activities were also observed in the BFT3 group (p < 0.05), while lipase activity did not changed. Muscle glutathione (GSH) and malondialdehyde levels and catalase activity did not show significant differences among the experimental treatments (p > 0.05). On the other hand, the highest superoxide dismutase activity and total antioxidant capacity (TAC) was observed in BFT10 (p < 0.05). Body proximate composition of L. vannamei was not significantly different in experimental groups (p > 0.05). Our findings showed that biofloc system could overcome the reported adverse effects of salinity on L. vannamei growth and possibility of rearing L. vannamei in low salinity in the biofloc system.

Schizothorax oconnori has evolved various adaptations to the region’s extreme conditions, including low temperatures and high altitudes. This study showed that the full‐length open reading frame (ORF) of the SoCyp19a gene reveals a sequence encoding a 517 amino acid protein. SoCyp19a protein shares high sequence identity with other fish species’ Cyp19a proteins. SoCyp19a is predominantly expressed in the ovaries, with significantly higher mRNA levels in females compared to males. The gene exhibits sexual dimorphism, with notable expression in the ovaries and moderate expression in the pituitary. This study offers a foundation for future research on the species’ reproductive biology.

The Chinese soft‐shelled turtle ( Pelodiscus sinensis ) is a valuable aquatic species with high economic and nutritional significance in China, and interstrain hybridization is a main breeding technique to improve the production and quality. In this study, we obtained the F5 generation through the process of interstrain hybridization between the Yellow River group (YR, ♂) and the Huai River group (HR, ♀), followed by successive selection to obtain the fifth generation (F5). This study aimed to assess the morphology, genetic diversity, and growth performance of the F5 progeny group. In total, 12 morphological traits were measured and revealed that male F5 progeny had a broad plastron and a long rostrum, whereas female F5 progeny appeared slender with smaller eyes. The contribution rate of the first three principal components (PCs) was 70.695%, primarily manifested in plastron width (PW), snout length (SL) and body height (BH). Genetic diversity was assessed by microsatellite simple sequence repeats (SSR) and mitochondrial DNA (mtDNA) markers (cytochrome b, cyt b). SSR analysis showed that the average observed heterozygosity ( H o ), expected heterozygosity ( H e ), and polymorphic information content (PIC) for the F5 progeny (0.769, 0.834, and 0.803) were smaller than those of the F0, which exhibited higher genetic diversity. Cyt b analysis showed that the number of haplotypes ( h ), haplotype diversity (Hd) and nucleotide diversity (Pi) of the F5 progeny (2, 0.125, and 0.0003) were also smaller than those of F0, suggesting significantly low genetic diversity. Cluster trees were constructed based on morphology and SSR results, respectively. The cluster tree based on morphology found that P. sinensis of the same gender were difficult to distinguish and clustered together initially. However, the SSR‐based clustering tree grouped the F5 progeny and the paternal into one category, while the maternal group formed a separate category. Based on the cyt b results, it was found that F5 and F0 likely shared the same maternal lineage. The growth performance showed that the feed conversion ratio (FCR) of the F5 progeny was significantly lower than the parents ( p < 0.05), and also exhibited the highest survival rate. Collectively, these findings suggest that the F5 progeny share a closer genetic relationship with the paternal parent and display superior growth performance compared to the parental generations. The cultivation of these hybrids has the potential to reduce production costs and facilitate widespread application.

The density of the hermit crab, Paguristes ortmanni, in the artificial reef of juvenile Apostichopus japonicus increased almost threefold from June to December 2018. Calcareous ossicles of A. japonicus were identified from the stomach contents in 28.8% of the hermit crabs (18.6% in males and 10.2% in females) in December; season hatchery‐produced juveniles are frequently introduced into the wild in Hokkaido, Japan. The mortality rate of juvenile A. japonicus by P. ortmanni was estimated to be 2.5 ± 2.4 individuals day−1 based on laboratory predation experiments. Interestingly, 3% to 5% of individuals survived despite being attacked and injured in all trials, escaping on the shells of hermit crabs. Over 50% of females in the ossicle‐not‐detected group had shield lengths (SLs) smaller than the smallest individual in the ossicle‐detected group. The average SL of the ossicle‐detected group in females was significantly higher (p< 0.01) than that of the not‐detected group, indicating an increased predation risk for A. japonicus juveniles when larger female P. ortmanni were present. The present study offers new insights into the predatory behavior of P. ortmanni toward A. japonicus juveniles, showing that these sympatric hermit crabs present a considerably high mortality risk to A. japonicus juveniles. It also emphasizes the importance of implementing appropriate measures to protect juveniles from predators during the release process, providing an essential viewpoint for enhancing and rebuilding the wild population of commercially important endangered A. japonicus.

Effective immune regulation and balanced gut microbiota play important roles in preventing pathogen infections in Litopenaeus vannamei farming. Bacteriophages are a promising candidate in pathogen control for their specific antibacterial properties. While previous studies focused on the direct antibacterial effects of phages, their effects on nonspecific immune responses and gut microbiota after infection remains to be less explored. In this study, a lytic Vibrio parahaemolyticus phage was isolated from wastewater with a broad host range (66.7% lytic efficiency), low multiplicity of infection (MOI; 0.1), and high environmental tolerance (pH: 3–11; temperature: 4–60°C). Whole genome analysis revealed a 93,814 bp double‐stranded linear DNA molecule with 45.1% GC. Both the in vitro cocultivation (24 h) and in vivo shrimp cultivation trails (7 days) demonstrated that phage could effectively reduce the quantities of Vibrio (>99%). The in vivo phage fed shrimp exhibited elevated levels of nonspecific immune‐related enzymes like alkaline phosphatase (AKP), catalase (CAT), superoxide dismutase (SOD), phenoloxidase (PO), and lysozyme (LZM) and upregulated immune‐related gene expression including those of antimicrobial peptides, pattern recognition receptors (PRRs), and pattern recognition proteins. Additionally, phage treatment improved the diversity of the gut microbiota (Shannon‐10 index) after Vibrio infection, indicating restored microbial balance in shrimp. These results suggest that phage therapy promotes nonspecific immune responses and repair intestinal dysbacteriosis in shrimp after Vibrio infection, elucidating a promising strategy to treat pathogenic Vibrio in shrimp aquaculture.

Gracilaria verrucosa and Ulva lactuca were cocultured with Crassostrea belcheri for 120 days in captivity while controls were the independent culture of these three species. The study assessed the water quality parameters, growth performance, proximate and biochemical composition of the organisms undergoing the different treatments. Moreover, they were compared with outdoor farmed seaweeds and oysters to assess their nutritional quality. Significant variations were seen in the growth rates of the two seaweeds, U. lactuca exhibiting the highest live weight gain (LWG) and specific growth rate (SGR) in coculture settings. The percentage of surviving oysters varied from 60% to 80% across experiments, with the fastest growth rates observed when cocultured with U. lactuca. The seaweeds’ moisture, ash, protein, carbohydrate, and fiber contents varied significantly, with U. lactuca (indoor) having the highest protein and carbohydrate content (p < 0.05) compared to U. lactuca (outdoor) and G. verrucosa (indoor and outdoor), and also recording the maximum total chlorophyl, carotenoids, and fucoxanthin. Significant variations were found in the fatty acid content of seaweed and oyster samples. Outdoor oyster samples had more omega‐3 fatty acids (p < 0.05) than indoor while the indoor seaweed samples had lower saturated fatty acids (SAFA), and higher polyunsaturated fatty acids (PUFA) than outdoor. U. lactuca grown indoors exhibited the highest levels of both essential amino acids (EAAs) and non‐essential amino acids (NEAAs). The study emphasizes how culture conditions affect the nutritional and biochemical profiles of seaweeds and oysters, and it offers indoor coculture as a potential substitute for inclement environmental conditions and as a backup strategy to enhance sustainable seaweed mariculture that allow for optimal growth and nutritional quality ensuring the maximum space utilization.