Smith River Steelhead and Coho Monitoring Verification Study, 2007, OPSW-ODFW-2009-11

Identification Information

Citation

Originator: Constable, R. J. Jr. and E. Suring

Publish Date: 2007

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Cedric Cooney

Job Position: Natural Resources Data and Systems Manager

Telephone: 503-947-6094

E-Mail Address: cedric.x.cooney@odfw.oregon.gov

Description

Abstract: We used electrofishing and snorkel surveys to estimate juvenile salmonid abundance and compared their ability to monitor the status and trends of fish populations at the basin scale. From electrofishing we estimated population size, densities, and pool occupancies in the wadeable portions of the basin. Density and pool occupancies were estimated from all pools in electrofishing sites and pools within these sites that met snorkel size criteria. Population estimates were made from all habitat types and pools that met snorkel size criteria. From snorkel surveys we estimated the same metrics in both the wadeable and non-wadeable portions of the basin, but only in pools that met size criteria. For sites where both surveys were conducted there was no detectable difference between electrofishing and snorkeling density estimates for coho. Snorkeling generated higher steelhead densities and electrofishing generated higher cutthroat densities. Coho and steelhead population estimates from electrofishing were not statistically different than coho and steelhead population estimates from snorkeling. Electrofishing population estimates were higher for cutthroat. Electrofishing detected 39% of juvenile coho and 37% of juvenile steelhead rearing in wadeable habitats not sampled by snorkeling. Snorkeling detected 21% of juvenile coho and 17% of juvenile steelhead rearing in non-wadeable stream reaches not sampled by electrofishing. Snorkelers sampled 3% (by length) of the steelhead rearing distribution in the study area. Electrofishers sampled 0.6% of the distribution. In pools that were sampled by both methods snorkelers counted 28% of the steelhead and 82% of the coho estimated by electrofishing, yet, by sampling a larger area, overall snorkeling produced similar density estimates for coho and higher density estimates for steelhead. Results from 2007 indicate that either method alone is likely to underestimate actual population status. Previous studies evaluating snorkeling and electrofishing have shown undercounting of coho and steelhead. More accurate estimates require a combination of both methods, refined habitat measurements, and calibrated snorkel counts such as described by Hankin and Reeves (1988). Data from 2007 indicate that neither method is statistically different from the other for estimating population status of juvenile coho or steelhead. Evaluation of these data show that juvenile coho densities for the two methods reflect increases and decreases in adult population estimates in the Smith River Basin. Coho densities from snorkeling tracked adult estimates better than densities from electrofishing. Steelhead density data did not track with adult estimates for all years. Steelhead densities from snorkeling tracked adult estimates better than densities from electrofishing. Steelhead densities may have a weaker correlation with adult numbers than coho because they are older fish when sampled and comprised of multiple cohorts. Additional years of data will improve statistical power and trend evaluations, increasing our ability to compare the two methods. Results from all years of this study will provide information on the relationship of the data generated from the coast-wide monitoring of juvenile salmonids using a snorkeling protocol at large scales and actual population status.

Purpose: Monitoring the status of salmonids in Oregon coastal streams is an important component of the Oregon Department of Fish and Wildlife’s (ODFW) contribution to the Oregon Plan for Salmon and Watersheds. Since 1998, ODFW has implemented a probabilistic sampling design (Stevens 2002) to monitor adult and juvenile coho in Oregon coastal streams. In 2002, ODFW expanded its monitoring program to include steelhead. Monitoring is occurring coast wide and relies on the Environmental Monitoring and Assessment Program (EMAP, Stevens and Olsen 1999) for site selection and to produce fish abundance metrics at large spatial scales. Juvenile monitoring is conducted using snorkel survey protocols. The Smith River Steelhead and Coho Monitoring Verification Study is an effort to evaluate how well visual counts compare with removal estimates as a monitoring tool at the basin scale and to provide information on the relationship of monitoring data collected coast wide to actual populations. This report will summarize juvenile salmonid data collected by snorkeling and electrofishing in the Smith River basin during the summer of 2007 and provide a comparative analysis of several years’ data of how the estimates from the two methods correspond to each other and to the spawning survey estimates of adult fish above Smith River Falls. Information on the relationship of coast wide snorkel counts on the basin scale to actual population status will be presented in a synthesis report covering all years of this study.

Time Period of Content: 2000-2007

Geographic Extent: Northwestern Douglas County, Smith River Basin above Smith River Falls

Status: Final

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Format: PDF File

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Is a physical copy maintained for reference at Headquarters? No