Performance of Two Strains of Rainbow Trout Reared at Four Densities with Supplemental Oxygen

Abstract

Abstract Wild and domesticated strains of rainbow trout (Oncorhynchus mykiss) were reared in triplicate groups at four fish densities in two separate studies. Fish weight gain, survival, length increase, length variability, feed conversion (weight fed/weight gain), dorsal fin condition, fish health, and water quality were monitored during each 4-month test. Dissolved oxygen was supplemented to maintain afternoon effluent oxygen levels at 6–7 ppm (61–71% saturation). Survival decreased with increasing density for both strains: wild strain survival was reduced because of cannibalism, and domesticated strain survival was reduced because of mechanical failures that reduced dissolved oxygen. Weight gain and total length increased with increasing densities for the wild strain, but the opposite occurred for the domesticated strain. Length coefficient of variation (SD/mean) increased directly with increasing fish density. Feed conversions of both strains were adversely affected by increased densities, but dorsal ...