Effects of stocking density on the survival and growth of Haliotis discus hannai ♀ × H. fulgens♂ hybrids

Abstract

In order to examine the effects of different stocking densities and culture methods on the growth, food intake and expression of related genes in Haliotis discus hannai ♀ × H. fulgens♂ hybrid abalones, juvenile abalones were placed into three treatment groups of different stocking densities (400, 600, 800 ind/m2) and cultured using two different methods, including suspension cages and bottom sowing. There were three replicates of each experimental group (stocking density and culture method) and the experiment lasted for 180 days. The results showed that the survival rate, specific growth rate of shell length and body weight, food intake and feed conversion efficiency of the abalones cultured in suspension cages were significantly lower than those in the bottom sown group. For abalones cultured by bottom sowing, there was no significant difference between the specific growth rate of shell length and body weight, feed conversion efficiency, α-amylase, cellulase activity and the expression levels of Hdlam on each sampling occasion for the 400 and 600 ind/m2 treatments. However, these parameters were significantly higher in both the 400 and 600 ind/m2 treatments compared with the 800 ind/m2 treatment. When the stocking density was increased to 800 ind/m2, the food intake and the expression levels of Hdaly, Hdcel, Hdamyl of the abalones cultured in both culture methods were significantly lower than the 400 and 600 ind/m2 treatments. This indicates that even with sufficient food supply, some abalones were unable to capture food due to the constraints of the culture space and the feeding method used by abalones, resulting in reduced growth. The findings of this research suggest that the growth and food intake of abalones can be promoted and production can be improved at a stocking density of 600 ind/m2.