In the present study, a Gram-positive bacterium was isolated from the intestine of healthy crucian carp Carassius auratus and named strain R8. It was initially identified as Enterococcus faecium according to its morphological, physiological and biochemical characteristics. Further identification by using 16S rRNA gene sequence analysis confirmed the R8 strain (Genbank accession no. MF928076) as E. faecium. Challenge and hemolysis experiments showed that the E. faecium R8 strain had no toxicity to the crucian carp. Bacteriostatic experiment showed that this isolate obviously inhibited the growth of Aeromonas veronii and Staphylococcus haemolyticus. The proliferation of E. faecium R8 strain occurred after exposure to various growth conditions such as at pH values from 2.0 to 4.0 for 8 h, bile concentrations from 0.2 to 1.2% and high temperature of 80 °C. This bacterial strain grew best under the condition of 37 °C, pH 7.0 and salinity 30 ppt, and its growth curve exhibited four distinct phases. These results showed that the E. faecium R8 strain had potential probiotic characteristics and could be used as a candidate strain for aquatic probiotics.

Ocean acidification (OA) can have widespread implications for marine bivalves. While our current understanding of OA effects on the physiological performance is increasing, very little is known about the physiology of digestive gland of marine bivalves in response to OA. Here, we examined how the digestive system of razor clams (Sinonovacula constricta) responded to OA. Following 35-day exposure to CO₂-driven seawater acidification, no significant decreases in phenotypic traits, such as dry body weight gain, specific growth rate, condition index and survival rate, as well physiological functions, such as activities of antioxidant and digestive enzymes, were observed, demonstrating the resistance of razor clams under acidified conditions. Histological results showed that some direct damages on the structure of digestive gland was observed, including degradation of digestive tubular, atrophy of epithelial cells, loose cell arrangement, even diffuse. This study provides insights into the digestive performance of marine bivalves in a rapidly acidifying ocean.

Aquaculture, a vital component of global food supply, faces challenges from environmental stressors that compromise aquatic animal health and productivity. Astaxanthin, a potent carotenoid antioxidant, has shown promise in enhancing growth and stress resilience in aquaculture species, yet its effects remain inconsistent across studies. This meta-analysis systematically evaluates the efficacy of dietary astaxanthin supplementation on growth, feed utilization, antioxidant capacity, and immune function in aquaculture animals. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 64 studies (33 species, 964 comparisons) published prior to 2025 were analyzed using a random-effects model. Results demonstrated that astaxanthin significantly improved final body weight, weight gain rate, specific growth rate, survival rate, and protein efficiency ratio, while reducing feed conversion ratio. Additionally, it enhanced digestive enzyme activities, hepatopancreas antioxidant biomarkers, and immune parameters. The subgroup analysis revealed differences related to species, trophic level, and habitat, and estimated the optimal dose for key indicators. Despite heterogeneity and publication bias, adjusted effect sizes remained significant for most outcomes. These findings underscore astaxanthin’s potential as a multifunctional feed additive to promote sustainable aquaculture, though its efficacy depends on species, dosage, and environmental context, warranting further mechanistic and optimization studies.

Chaetoceros muelleri and Isochrysis zhanjiangensis, known for their rapid reproduction, small size, and rich nutritional content, are commonly used as feed microalgae in aquaculture. This study aimed to sterilize these microalgal species and assess the effects of antibiotics on their algal cell density. Phycospheric bacteria were isolated and identified using the spread plate method and 16S rDNA sequencing, and antibiotic susceptibility tests were conducted using four antibiotics: ampicillin, streptomycin, kanamycin, and gentamicin sulfate. A sterile system was established for C. muelleri using ampicillin, streptomycin, and gentamicin, and for I. zhanjiangensis using kanamycin, ampicillin, and streptomycin. Based on the results, antibiotics with sterilization effects were selected and added to the algal cultures. Their effects on cell density were evaluated during a six-day co-culture. Ampicillin and streptomycin effectively inhibited bacteria associated with C. muelleri, initially increasing algal cell density but later causing a decline. For I. zhanjiangensis, kanamycin and ampicillin were effective, with kanamycin significantly promoting growth throughout the cycle, achieving a 36.92% higher cell density on day six (p < 0.05).

High-pressure processing (HPP) technology can significantly improve the texture and flavor of Mercenaria mercenaria. This study aimed to investigate the effect of HPP treatment with varying levels of pressure (100, 200, 300, 400, 500, and 600 MPa) and a holding time of 8 min at 20 °C on the physicochemical properties and volatile flavors of M. mercenaria. The significant changes in hardness, resilience, and water holding capacity occurred with increasing pressure (p < 0.05), resulting in improved meat quality. Scanning electron microscopy (SEM) was utilized to observe the decomposition of muscle fibers in M. mercenaria due to varying pressures, which explains the differences in texture of M. mercenaria. Different pressure treatments also had an influence on the volatile flavor of M. mercenaria, and the quantities of low-molecular-weight aldehydes (hexanal, heptanal, and nonanal) with a fishy taste decreased dramatically following 400 and 500 MPa HPP treatments. Furthermore, the level of 2-Methylbutyraldehyde, which is related to sweetness, increased significantly following 400 MPa HPP treatment. The study found that 400 MPa HPP treatment resulted in minor nutrient losses and enhanced sensory quality. The results of this study provide a theoretical basis for the application of HPP treatment to M. mercenaria.