Study on the effects of stocking density of eggs and larvae on the survival and frequency of morphological deformities in Persian sturgeon, great sturgeon and stellate sturgeon

Abstract

The effects of stocking density of eggs and larvae were studied related to the morphological deformities appearance, percentage of survival, and growth rate, in order to achieve the most suitable stocking density for eggs and larvae in incubators and rearing tanks. The egg stocking densities were 500, 700 and 900 g per incubator for great sturgeon, 500 and 1000g per incubator for Persian sturgeon and 400 and 425g per incubator for stellate sturgeon. Larvae were stocked at densities of 10000, 15000 and 20000 larvae per m3 for great sturgeon, 21660, 41004 and 69000 larvae per m3 for Persian sturgeon and 15770, 23250, 57660 and 62250 larvae per m3for stellate sturgeon. The results indicate significant differences in percentage of survived in fertilized eggs (p < /em><0.05). By transferring the larvae into the fibreglass tanks, growth and survival rate decreased, whereas mortality and incidence of deformities increased as stocking density increased particularly on the onset of exogenous feeding. In the present study totally 20 types of deformities including bent spine, hunched back, hanging or looped tail, fin deformation, stunted body length and etc. were registered. The results showed that the morphological deformities frequency in dead and live fish were higher in high stocking densities comparing to the low stocking densities.