Mario F. Solazzi

Comparison of Three Techniques to Estimate Juvenile Coho Salmon Populations in Small Streams

Abstract Mark-recapture, removal, and snorkel population estimates were compared with a known number of juvenile coho salmon Oncorhynchus kisutch stocked in 18 pools in the same stream during the summer. The effects of fish density, pool size, and habitat complexity on the percentage of the actual population estimated by the three methods were examined. Mark–recapture estimates were also compared with known numbers of juvenile coho salmon stocked in six pools in the same stream during the winter, and snorkel counts were compared with mark–recapture estimates obtained in other Oregon coastal streams during the summer and winter. After all pool sizes and fish densities were combined, during the summer 85% of the actual number of fish present were accounted for by mark–recapture, 67% by removal, and 40% by snorkel counts. Summer pool surface area explained 44% of the variation in the accuracy of mark–recapture estimates. Pool surface area and the percentage of the pool volume taken up by rootwads explained 7...

Transportation stress affects performance of coho salmon, Oncorhynchus kisutch

Abstract Transportation of yearling coho salmon ( Oncorhynchus kisutch ) from their hatchery by trucking caused a marked physiological stress response, as judged by elevations in concentrations of circulating cortisol. Survivorship, as determined by recoveries of adults at sea and at the hatchery, was reduced in fish not given adequate time to recover from this transportation stress before they were released into their migratory stream. Elevated concentrations of plasma cortisol indicated reduced relative fitness of the stressed fish, as evidenced by the lower survival rates to adulthood for fish liberated while their circulating cortisol titers were still high.

Genetic Variation in Steelhead of Oregon and Northern California

Abstract Steelhead Oncorhynchus mykiss from various sites between the Columbia River and the Mad River, California, were genetically characterized at 10 protein-coding loci or pairs of loci by starch gel electrophoresis. Fish from coastal streams differed from fish east of the Cascade Mountains and from fish of the Willamette River (a tributary of the Columbia River, west of the Cascade Mountains). Coastal steelhead from the northern part of the study area differed from those in the southern part. Genetic differentiation within and among drainages was not statistically significant; however, gene diversity analysis and the life history of steelhead suggested that fish from different drainages should be considered as separate populations. Genetic variation among fish in separate drainages was similar to that reported in northwestern Washington and less than that reported in British Columbia. Allele frequencies varied significantly among year-classes. Genetic variation within samples accounted for 98.3% of t...

Effects on Survival and Homing of Trucking Hatchery Yearling Coho Salmon to Release Sites

Abstract Effects of transporting yearling coho salmon Oncorhynchus kisutch to release sites in Oregon coastal river systems were determined by comparing survival of fish transported before release to that of fish released without being transported. Ocean catches of fish transported before release ranged from 43 to 113% of those for control fish within years. Over 4 years, ocean catches of fish trucked and returned to the hatchery for release, trucked and released upstream from the hatchery, and trucked and released in a tributary downstream from the hatchery averaged 76, 83, and 84% of ocean catches of untrucked fish. For yearling coho salmon trucked to another Oregon coastal river system for release, fish acclimated at the release site for 6 weeks before release showed consistently higher survival than groups released immediately upon arrival at the release site. Almost all returning adult fish released as yearlings at a site 23 km upstream from the rearing hatchery returned to the rearing site, whereas ...

An Automated Device to Release Marked Juvenile Fish for Measuring Trap Efficiency

Abstract We describe a floating device that allows for the automated release of juvenile salmonids into rivers and streams at a predetermined time. This device is useful in studies using floating traps to estimate the number of downstream-migrating juvenile salmonids. The device assists these projects by enabling the release of fish at dusk, when juvenile salmonids typically begin to move downstream. Release of fish at dusk or night is preferable to daylight releases to reduce potential predation on juvenile fish. This device eliminates the need for project personnel to remain at the release site to perform this function.