This study examined the survival rates of Anadara broughtonii and Chlamys farreri with varying heights throughout winter and summer aquaculture periods under varying ratios of mixed-culture conditions in marine environments. The aim was to assess the viability and economic advantages of mixed-culture practices among different bivalve species. Results indicate that the winter (from December to February of the following year) mortality rate for A. broughtonii in mixed culture ranges from 12.04% to 16.85%, markedly lower than in single-species cultures. Mixed-culture A. broughtonii measuring 2.5–4.0 cm exhibit a significantly reduced summer (from July to September) mortality rate compared to those in single-species cultures (p < 0.05). No significant mortality difference was observed between the monoculture and polyculture of C. farreri. Growth rates of C. farreri and A. broughtonii showed no significant differences between monoculture and polyculture conditions. The optimal size for combining two different species of bivalves is 2.5 cm, with a 1:1 ratio being the most effective. An equal number of seedlings were cultivated across various seawater aquaculture systems for a period of one year. The survival rates of monoculture seedlings of Anadara broughtonii and Chlamys farreri were 60.34% and 86.55%, respectively. In contrast, polyculture seedlings exhibited higher survival rates after one year of mariculture, with Anadara broughtonii at 73.36% and Chlamys farreri at 89.74%. The polyculture of A. broughtonii and C. farreri in suspension cages demonstrates a favorable input–output ratio of 1:2.02. This approach effectively reduces winter and summer mortality rates of A. broughtonii, representing an efficient new method for marine bivalve aquaculture.

DNA methylation is known to play an important role in the regulation of gene expression in eukaryotes. In this study, the author assessed the extent and pattern of cytosine methylation in the Scapharca broughtonii genome using the technique of methylation-sensitive amplified polymorphism (MSAP).The results showed that, DNA methylation rate was negatively related to the shell length, the gross weight and the weight of soft body, but positively related to the shell broadness and the shell height; there was significantly different between the parents and the offspring: 31.6% of 5'-CCGG sites in the Patinopecten yessoensis of Korean populations genome were cytosine methylated, and in the Patinopecten yessoensis of Chinese populations were 33%, the methylation rates of F1 was 29.98%; four classes of patterns were identified in a comparative assay of cytosine methylation in the parents and hybrid, increased methylation was detected in the hybrid compared to the parents at some of the recognition sites, while decreased methylation in the hybrid was detected at other sites. It indicated that the alteration of methylation resulted from cross-breeding, and the inbreeding did not change the methylation ratio and patterns; The DNA cytosine methylation has a relationship with the heterosis.

The study examines the survival status of Scapharca broughtonii and Scallop Chlamys farreri under diverse seasons, sizes, and mixed breeding ratios. The objective is to explore the feasibility and economic benefits of the mixed breeding patterns of different shellfish varieties. The findings demonstrate that the overwintering mortality rate of mixed-cultured S.broughtonii ranges from 12.04% to 16.85%, which is conspicuously lower than that of individually cultured S.broughtonii. The summer mortality rate of mixed-cultured S.broughtonii with a size of 2.5 - 4.0 cm is significantly lower than that of individually cultured S.broughtonii (P < 0.05). There is no notable difference in the mortality between monoculture and polyculture of C.farreri. There is no significant disparity in the growth of C.farreri and S.broughtonii in monoculture and polyculture. The optimal polyculture size of the two scallops is 2.5 cm, and the ideal polyculture ratio is 1:1. The co-culture model of S.broughtonii and C.farreri in suspension cages has a high input-output ratio (1:1.9). It can effectively lower the winter and summer mortality rates of ark clams, representing an efficacious new methodology for marine shellfish farming.

To understand the dissolved oxygen tolerance of Hippocampus abdominalis during transportation or cultivation at different water temperatures, this study investigated the patterns of oxygen consumption and activity changes in H. abdominalis (with body lengths of 11.55-12.05 cm and weights of 4.60-6.19 g) as the dissolved oxygen (DO) levels in the water decreased. The experiment utilized the static water respiration chamber method, using a water bath to control the temperature with a variation not exceeding 1℃. Three experimental temperature gradients were designed: 14℃, 19℃, and 24℃, with three repetitions for each group and a blank control group set for comparison. Results showed‌: suffocation point (±SD) were (0.18±0.03) mg/L at 14°C, (0.20±0.05) mg/L at 19°C, and (0.21±0.02) mg/L at 24°C. Elevated temperatures reduced DO saturation levels and increased the suffocation point. During the asphyxiation phase (Phase I: onset to first death), oxygen consumption rates (OCR) were 0.29 mg/(g·h), 0.46 mg/(g·h), and 0.51 mg/(g·h), respectively at three temperatures. During the mortality phase (Phase II: first death to 100% mortality), OCR were 0.02 mg/(g·h), 0.01 mg/(g·h), and 0.01 mg/(g·h). Under salinity 28.25 and pH 8.54, both DO parameters and suffocation point exhibited temperature dependency. Phase I OCR increased with temperature, with 14°C group significantly lower than 19°C/24°C groups. Phase II OCR at 14°C was slightly higher than in other groups. All groups showed a significant OCR decline with DO reduction. H. abdominalis employed a ‌conformist respiratory strategy, modulating oxygen consumption to adapt to hypoxia. Metabolic rates rapidly escalated during asphyxiation but minimized under critical hypoxia with narrow DO variation margins. The study demonstrates‌an immediate high-oxygen-consumption response under DO stress. Poor hypoxia tolerance with stringent DO requirements. Dissolved oxygen is closely related to fish metabolism and energy consumption. The large-scale breeding of juvenile seahorses requires stringent conditions, where high-quality germplasm supply is a prerequisite for successful breeding, and the survival rate during transportation ensures the stable supply of germplasm. Real-time monitoring of DO levels, combined with behavioral observations, is essential for standardizing protocols in aquaculture and transport operations. This study provides theoretical support for oxygen management during transportation by quantitatively analyzing the oxygen consumption rate.

Saxidomus purpuratus (S. purpuratus) is an economically important bivalve along the northern coast of China, where intensifying fishing pressure threatens its wild stocks. Its genome-wide population genetic variation remains poorly characterized. We resequenced 75 wild individuals from five populations spanning the northern Yellow Sea (Donggang, DDDG; Ganjingzi, DLGJ; Huancui, WHHC) and the Bohai Sea (Changdao, YTCD; Laizhou, YTLZ). The sampled populations exhibited relatively low genetic diversity (He = 0.1301–0.1324), weak among-population differentiation (Fst = 0.0035–0.0040), and heterozygosity deficiency (Fis = 0.0480–0.0831). PCA, NJ, and ADMIXTURE detected no geographic structure. PSMC revealed concordant demographic histories, with a sustained decline following a Middle Pleistocene expansion, consistent with historical allele exchange. Selection scans (DDDG as the target population; WHHC and YTCD as references) identified 1268 candidate genes, of which 197 were shared across the two comparisons. After masking a tandem histone gene cluster, the remaining 155 non-histone genes fell into five functional categories: receptor and signal transduction, membrane transport and ion channels, innate immunity and defense, extracellular matrix and adhesion, and detoxification and metabolism. These signals recurred in both comparisons, identifying DDDG as a candidate population for genotype–environment association testing. Together, these results indicate that the five populations constitute a single genetically connected unit, while pinpointing a small set of candidate loci that may underpin local adaptation and should inform stock-enhancement programmes.