Homing of coho salmon ( Oncorhynchus kisutch) exposed to morpholine

Smolts of coho salmon ( Oncorhynchus kisutch) were exposed to 5 × 10 −5 mg·l −1 morpholine for 15 days and released into the Salmon River along with an unexposed control group. During the following two autumns, morpholine was introduced into the hatchery's fish ladder on various days and the return of experimental fish was recorded. The returns of morpholine-exposed and control fish were not statistically different. With morpholine present in the fish ladder, control fish were not repelled, and with morpholine absent from the ladder, morpholine-exposed fish returned as readily as control fish.