Effects of transportation timing on osmoregulation and survival in yearling hatchery Chinook salmon (Oncorhynchus tshawytscha)

Seasonal timing of transportation and acclimation of juvenile Chinook salmon (Oncorhynchus tshawytscha) between hatcheries may affect osmoregulation and survival. We investigated the duration of time fish need to acclimate to hatchery conditions prior to being presented with a saltwater challenge. We monitored acute survival and osmoregulatory ability following a 24-h saltwater challenge of fish previously transported to a hatchery at various times throughout the year compared to fish reared at that hatchery. Fish that underwent a saltwater challenge 3 weeks after transport had significantly reduced osmoregulatory performance and increased mortality compared to fish allowed an acclimation period of 2 months.