Acclimation and Release Strategies to Improve Imprinting and Homing Fidelity of Hatchery-Reared Salmon

The need to rear salmon at large centralized hatcheries and then release them offsite to supplement specific populations or fisheries is a practical reality of artificial production. However, this practice can dramatically increase stray rates and stray hatchery fish are one of the major threats to the recovery of endangered salmon populations. Accurate homing of hatchery salmon to ensure spatial segregation of hatchery and wild fish (or for conservation supplementation programs, integration of hatchery and wild fish) is critical for salmon management and conservation efforts. Homing is governed by the olfactory discrimination of home-stream water and exposure to the home stream during appropriate juvenile stages is critical for olfactory imprinting and successful completion of the adult homing migration. In particular, the parr-smolt transformation has been demonstrated as a critical period for olfactory imprinting and most hatchery programs use this as a guiding principal for designing release strategies that will return fish to targeted locations. In this presentation, I review current rearing and release strategies to reduce straying of hatchery fish. Furthermore, I will describe alternative approaches that may be useful for achieving successful imprinting and homing fidelity to target spawning locations.