Science activity

Hatchery-reared fish have been used to supplement endangered winter-run Chinook salmon in the upper Sacramento River since 1989. Intense drought in the past five years has led fisheries managers to substantially modify their hatchery protocols, increasing the total number of fish released and using hatchery-origin adults for producing juveniles. However, the impact of these practices is not fully understood. This project evaluated multiple aspects of how hatchery–reared fish contribute to natural production of winter-run Chinook salmon in the upper Sacramento River. The researchers assessed whether hatchery-reared fish are spawning in the wild and producing natural-origin offspring using a novel panel of genetic markers developed during the study. The study also assessed if inadvertent domestication selection was occurring in the hatchery during the drought years and if more highly related hatchery broodstock pairings returned fewer offspring than less related pairs.