Comparison of Midsummer Survival and Growth of Age-0 Hatchery Coho Salmon Held in Pools and Riffles

Abstract

Habitat use studies have shown that juvenile coho salmon Oncorhynchuskisutch select pools over riffles. However, stream alterations havecaused pool habitat to be lost or degraded throughout the PacificNorthwest. This study compared the growth and survival of age-0 cohosalmon in riffles and pools in four streams in the South Umpqua Riverbasin, Oregon. Hatchery coho salmon were stocked in block-netted rifflesand pools. At the end of the study, the fish were recovered in order tomeasure their growth and survival in each habitat type. The survival ofcoho salmon was significantly higher (P < 0.01) in pools (67%) than inriffles (27%). This variation in survival was related primarily towater depth. The growth of coho salmon did not differ significantly (P >0.05) between pools and riffles. The condition factor of the coho salmonwas significantly (P < 0.05) lower at the end of the experiment but didnot differ between fish in pools and riffles (P > 0.05). The results ofthis study suggest that land management activities that reduce poolhabitat may also reduce juvenile coho salmon survival or rearingcapacity in small streams.