Effects of Rearing Density on Meristics and Developmental Stability of Rainbow Trout

Abstract

We investigated the effects of a four-fold difference in incubation and rearing density on developmental rate, counts of eight meristic characters, and fluctuating asymmetry of rainbow trout, Oncorhynchus mykiss. Fish from the high density group had significantly more vertebrae and rays in the pelvic fins. The overall magnitude of morphological divergence between treatment groups, however, was small compared to that associated with genetic and temperature-induced alterations of developmental rate. Fish from the high density treatment had greater mean fluctuating asymmetry than those in the low density group, but this difference is not statistically significant. Hatching time did not differ significantly between treatment groups. The effects of density on meristic counts, therefore, appear to be independent of developmental rate.