Background-Color Acclimation of Brook Trout for Crypsis Reduces Risk of Predation by Hooded MergansersLophodytes cucullatus

In a laboratory study, fry of brook trout Salvelinus fontinalis experienced less predation by hooded mergansers if they were previously acclimated for 11–12 weeks to tanks having the same background color as the predation arena. Color acclimation produced morphological color changes that rendered the fish more cryptic to the birds. Overall, cryptic brook trout accounted for 37% of predation, whereas unmatched fish experienced 63% of the total predation mortality. Implications of this study for salmonid management are that reduced predation of transplanted fish will occur if they are acclimated in hatcheries to backgrounds having similar coloration to the gravel in the habitat where they will be transplanted.