Outmigration Behavior and Marine Survival As a Function of Rearing Habitat for Coho Salmon in the Shasta River, CA

The Shasta River has been subjected to a slew of adverse conditions leading to degradation of fish habitat. Juvenile Coho Salmon exposed to these conditions outmigrate early to seek suitable rearing conditions. Big Springs Creek, a tributary to the Upper Shasta, maintains ideal habitat with spring-fed hydrology, creating rearing environments year-round.  Outmigrating juvenile Coho Salmon were tagged with Passive Integrated Transponder (PIT) tags in the lower canyon region of the Shasta River in spring of 2014 and 2015. Subsequently, remote antennas and unique sampling efforts were used to monitor their movement and survival.  The tagged sample size was supplemented using Scott River juveniles. Otolith samples from the Shasta River, the Scott River, and other similar sites will be utilized to determine juvenile rearing strategies of adults returning to spawn.  Strontium microchemistry analysis will compare water signatures within the natal and rearing regions of the otolith. Results will help indicate where the spawning adult reared, using natal or non-natal habitat.  Determining the proportion of individuals employing each life history strategy will clarify patterns of relative survival by rearing method.  Understanding the life history of this threatened species, especially during a critical fresh water life stage, can help improve future conservation strategies.