The Influence of Habitat Characteristics on Juvenile Coho Salmon Abundance and Growth in Constructed Off-Channel Habitats in the Middle Klamath River Subbasin

Humans have altered low gradient stream reaches in the Klamath River basin, disconnecting floodplains and decreasing the amount of available rearing habitat for juvenile Coho Salmon. In response, numerous off-channel habitats have been constructed in tributaries of the middle and lower Klamath basin to provide both summer and winter rearing habitat for juvenile Coho Salmon and help mitigate their declines. These habitats can provide seasonal refuge from high winter flows and also suitable summer habitat when water temperatures increase in the mainstem Klamath River.  Previous research in the middle Klamath has shown that these constructed habitats perform similarly to natural habitats. The juvenile Coho Salmon growth rates, abundance, and retention in constructed sites were not significantly different from natural sites, however they were significantly different between individual sites. It is not clear what mechanisms are responsible for the differences in performance among the constructed habitats. Our study investigates the effect of habitat characteristics and food availability in constructed off-channel habitats on juvenile Coho Salmon growth and abundance to determine if ponds constructed for habitat restoration and salmonid survival do provide suitable and beneficial summer habitat.