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

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 ۵۰۰, ۷۰۰ and ۹۰۰ g per incubator for great sturgeon, ۵۰۰ and ۱۰۰۰g per incubator for Persian sturgeon and ۴۰۰ and ۴۲۵g per incubator for stellate sturgeon. Larvae were stocked at densities of ۱۰۰۰۰, ۱۵۰۰۰ and ۲۰۰۰۰ larvae per m۳ for great sturgeon, ۲۱۶۶۰, ۴۱۰۰۴ and ۶۹۰۰۰ larvae per m۳ for Persian sturgeon and ۱۵۷۷۰, ۲۳۲۵۰, ۵۷۶۶۰ and ۶۲۲۵۰ larvae per m۳for stellate sturgeon. The results indicate significant differences in percentage of survived in fertilized eggs (p<۰.۰۵). 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 ۲۰ 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. 

Keywords:

Great sturgeon , Persian sturgeon , stellate sturgeon , Morphological deformities , Stocking density , Larval survival