Imprinting of Hatchery-Reared Salmon to Targeted Spawning Locations: A New Embryonic Imprinting Paradigm for Hatchery Programs

Straying by hatchery-reared salmon is a major concern for conservation and recovery of many salmon populations. Fisheries managers have attempted to minimize negative ecological and genetic interactions between hatchery and wild fish by using parr-smolt acclimation facilities to ensure successful olfactory imprinting and homing fidelity. However, the effectiveness of offsite acclimation for returning adults to targeted locations has been mixed. Since laboratory and field studies indicate that the period of hatching and emergence from the natal gravel is a sensitive period for olfactory imprinting, we propose an alternative imprinting approach wherein salmon are exposed as embryos to targeted waters transferred to their rearing hatchery. To test the feasibility of this approach, we conducted a series of electrophysiological and behavioral experiments to determine whether water can be successfully transferred, stored, and treated for pathogens without jeopardizing its chemical integrity. Stream water could be frozen or stored for one week at 4° or 10° C without affecting the olfactory signature. Ultraviolet light treatment altered the responses of the olfactory epithelium to stream water; however, behavioral studies suggested that this treatment did not alter the attractiveness of this water. Finally, we describe several alternative approaches to embryonic imprinting using artificial odors.