Effects of body color luminance and behavioral characteristics on predation risk in salmonid fishes

We investigated the effects of body color luminance and behavioral characteristics of stocked juvenile white-spotted charr, masu salmon, rainbow trout, albino rainbow trout, and non-spotted rainbow trout on their predation risk by predatory land animals. Body color luminance and behavioral characteristics were scored before starting the predation test. The dorsal color luminance of the albino rainbow trout was brighter than that of the other fish. The white-spotted charr and non-spotted rainbow trout were less active than the masu salmon and rainbow trout, and the non-spotted rainbow trout stayed in the open more than the white-spotted charr during behavioral observations in an aquarium. A piscivorous bird, the grey heron was the most frequently observed land animal during the predation test conducted at a semi-natural stream study site. The survival rate of total fish groups was 21.4 %, only 3 % albino rainbow trout and 11 % non-spotted rainbow trout survived, which were significantly lower than the survival rate of the other fish. These results suggest that the body color luminance of albino rainbow trout and the behavioral characteristics of non-spotted rainbow trout were important vulnerability factors.