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SUMMER STREAM TEMPERATURES, JUVENILE COHO CONDITION FACTORS AND BLACK SPOT INFECTION IN THE OREGON COAST RANGE
Citation:
Cairns, M A., J L. Ebersole, H. Lavigne, J P. Baker, AND S. M. Davis. SUMMER STREAM TEMPERATURES, JUVENILE COHO CONDITION FACTORS AND BLACK SPOT INFECTION IN THE OREGON COAST RANGE. Presented at Oregon Chapter American Fisheries Society, Eugene, OR, February 26-28, 2003.
Description:
We monitored stream temperatures at 35 locations throughout the West Fork Smith River watershed in the Oregon Coast Range during the summer of 2002. Between July 24 and August 24, maximum seven-day moving average high daily temperatures ranged from 21.8 C near the catchment's mouth to 17.5 ?C in the upper main stem and from 16.8 C to 17.2 ?C in the lower reaches of three major tributaries. Juvenile coho occurred throughout the network although fish densities, based on pool snorkel counts, were generally lower in the lower main stem than in the upper main stem, and lower in the main stem than in the tributaries. Presence on juvenile coho of black-spot infections, identified as the parasitic trematode Neascus spp., was more frequently noted in main stem reaches than in adjacent lower tributary reaches. We computed condition factors for groups of coho juveniles in three lower tributary reaches and the corresponding main stem reaches. Preliminary results indicate that condition factors for coho without Neascus were higher than those for infected fish. We investigated possible statistical relationships among black-spot occurrence/severity, high summer temperatures, and condition factors in the West Fork Smith River watershed.