Juvenile Salmonid Survival in Specific Areas of the Nehalem Watershed - Annual Report

Identification Information

Citation

Originator: Schreck, Carl B., Daniel D. Roby, Shaun Clements, and Mark Karnowski

Publish Date: September 2002

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Carl Schreck

Job Position: Principal Investigator

Telephone: (541) 737-1961

E-Mail Address: carl.schreck@orst.edu

Description

Abstract: Mortality of wild steelhead in Nehalem Bay was estimated to be 54%, as assessed by acoustic telemetry throughout the outmigration season on five separate dates. The majority of this loss occurs in the very short (~2 km) region between the lower part of the estuary and the ocean. Likely predators included double-crested cormorants, and harbor seals, other cormorants, great blue herons, and Caspian terns. Movement between individual fish was variable in the river and appears to be related to river flow and precipitation. Significant changes in the behavior of fish were observed over time. The majority of fish migrated to the estuary during the first part of the season (April to early May). However, fish that were captured in the smolt trap in the latter part of the run (late May to June) tended to remain in the river even though they may have been moving on a more limited basis. Residence times of fish in the estuary tended to be less than a day. No differences in length, condition factor, stress, or disease, which can affect migration and saltwater entry, were evident between releases of smolts. No trends existed between mortality and migration behavior for the releases. Double-crested cormorants were the most abundant avian predator. No relationship between cormorant numbers and smolt mortality or total smolt numbers in Nehalem existed, though they overlapped with smolts spatially. Because the present study represents only the initial field season, this work needs to be finalized to better understand the relationship between smolt behavior, predation, and management measures.

Purpose:

Time Period of Content: 2001

Geographic Extent: Nehalem Bay and Lower Nehalem River

Status: Final

Use Constraints:

Format: PDF file

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Data Information

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Attributes Description: Field attribute information is available in the attached file(s).

Is a physical copy maintained for reference at Headquarters? No