Effects of water quality on the hatching of rapa whelk ( <i>Rapana venosa</i> ) eggs and larvae

To detect the effects of water quality factors on the hatching of Rapana venosa eggs, the eggs were exposed to controlled conditions with different concentrations of ammonia nitrogen and nitrite and different pH values respectively, for 60 days. The hatching rate, larval release time, and initial larvae sizes after hatching were documented and analyzed. Egg capsules had 100% mortality at pH ranges of 6.0-7.00 and 9.00-10.00, and the mortality rate was relatively low between pH of 7.50-8.50. With an increase in pH within this range, mortality decreased. Larval release times were also significantly affected by pH. Within the pH range of 7.50-8.50, the shortest larval release occurred at a pH of 8.5 and the longest at a pH of 7.5. Ammonia nitrogen had significant effects on larval body length and length to width ratio, with larval length increasing with decreasing ammonia nitrogen concentrations, whereas the ratio of length to width increased with decreasing ammonia nitrogen concentrations. Nitrite concentration had significant effects on the larval body length and ratio of length to width. In addition, pH had significant effects on larval body width and the length to width ratio. With increasing pH, larval body width decreased, whereas the ratio of length to width increased. This study explores the optimal growth conditions for the Rapana venosa , providing theoretical guidance for its industrial aquaculture and the conservation of wild resources.