RESPONSE OF THE YABBY, CHERAX DESTRUCTOR CLARK, TO NATURAL AND ARTIFICIAL DIETS - PHENOTYPIC VARIATION IN JUVENILE GROWTH

A comparison of juvenile growth performance amongst families of the fr eshwater crayfish, C. destructor was carried out under laboratory cond itions. Three diets, consisting of two pellet diets (15% and 30% prote in) and zooplankton, were fed to the juvenile crayfish which were obta ined from three families selected randomly from a genetically heteroge neous stock, Juvenile crayfish were stocked at l 1(-1) in 12 1 tanks a nd did not differ in weight amongst broods at the commencement of a 35 day trial. Growth and survival were found to differ with respect to d iet, with zooplankton giving higher growth and greater survival. Growt h, but not survival, differed by phenotype with the degree of differen ce in growth amongst families being dependent, at least in part, upon diet. Diet was also found to have a pronounced effect on the degree of variability in crayfish size within tanks with zooplankton fed animal s showing substantially lower levels of variability compared with pell et fed animals of equivalent size.