Background With the shellfish aquaculture industry developing and wild resources declining, the demand for blood clam (Scapharca subcrenata) seedlings is increasing. However, in northern China, the seed breeding technology for this species remains unstable. Enhancing larval survival and metamorphosis rates, reducing growth duration, and producing high-quality, fast-growing seeds are crucial for successful seedling cultivation in this region. Algae species and stocking density significantly influence the breeding process and are more manageable compared to other environmental factors. This study aims to explore the impacts of algae species and stocking density on the growth and development of blood clam larvae in northern China, where such research is currently lacking.

Methods Single factor analysis of variance (ANOVA) and multiple comparison analysis (Duncan) were employed for data analysis in this study. The study investigated the effects of algae species and stocking density on the growth and development of blood clam larvae under controlled conditions of 24.2−27.5°C water temperature, salinity of 26−27, and pH ranging from 8.2 to 8.5. Six algae groups were tested: Isochrysis zhanjiangensis, Chaetoceros mulleri, Chlorella saccharophila, combinations of I. zhanjiangensis with C. mulleri and C. mulleri with C. saccharophila, and a mix of I. zhanjiangensis, C. mulleri, and C. saccharophila. Stocking density was varied across five levels: 2, 5, 10, 15, and 20 ind/mL.

Results The results indicated that larvae fed solely with C. mulleri exhibited superior growth and development, while those fed with C. saccharophila showed the poorest performance. Mixed feeding regimes outperformed single algae diets, with larvae fed a combination of I. zhanjiangensis, C. mulleri, and C. saccharophila demonstrating the highest growth, survival, and metamorphosis rates. Additionally, increasing stocking density correlated with decreased larval growth, survival, and metamorphosis rates, with marginal differences observed between the 5 ind/mL and 10 ind/mL groups during the creeping stage.

Conclusion In the artificial cultivation of blood clam, it is recommended to avoid relying on C. saccharophila as the primary algae source, favoring single feeding of C. mulleri instead. Optimal juvenile yields were achieved by feeding a mixed algae diet containing C. mulleri, particularly at a stocking density of 10 ind/mL during the floating stage and between 5 to 10 ind/mL during the postlarval stage.

Significance  This study provides robust theoretical support and significant guidance for the seed breeding of blood clam under ambient temperatures in northern China. The findings are poised to advance the blood clam aquaculture industry.