Seasonal growth, retention, and movement of juvenile coho salmon in natural and constructed habitats of mid-Klamath River

Juvenile coho salmon (Onchorynchus kisutch) in the Klamath River basin often move long distances when natal streams become inhospitable due to high summer temperatures and high winter flows. Therefore, non-natal rearing sites such as tributaries and off- channel ponds are potentially important to the survival of juvenile coho salmon. This study evaluated the potential benefit to juvenile coho salmon of different types of non-natal rearing habitats in the mid-Klamath watershed including tributaries, beaver-influenced ponds, and constructed off-channel ponds. These sites represent different types of seasonal refugia habitat. Juvenile coho salmon were PIT tagged and measured in ten study sites to evaluate their growth, retention within the habitats, and seasonal movement patterns. Growth rate of fish which reared year-round in the same site was greater in beaver-influenced sites than in other habitat types. Depth, water temperature, volume of habitat, and percent riparian cover were not correlated with growth rates of coho salmon rearing in those sites. However, because I found significant differences in growth rates of fish across individual sites, there may be other habitat characteristics not measured as part of this study that influence growth. Retention rate was positively correlated with average maximum depth; however the summer retention rate of juvenile salmon at the sites was not correlated with salmon growth at the sites. I observed three seasonal movement patterns of juvenile coho salmon: spring redistribution of fry; fall redistribution associated with initial high flows, and outmigration of smolts during the following spring. This exploratory study showed that not only do juvenile coho salmon in the mid-Klamath display several different migratory patterns; choosing different types of off-channel habitats to rear, but the growth and retention rates of those fish depend on complex and site specific characteristics rather than type of habitat.