Smolt Migration Characteristics And Mainstem Snake And Columbia River Detection Rates Of Pit Tagged Grande Ronde And Imnaha River Naturally Produced Spring Chinook Salmon PDF Download

This is the fifth year of a multi-year study to assess smolt migration characteristics and cumulative detection rates of naturally-produced chinook salmon (Oncorhynchus tshawytscha), from northeast Oregon streams. The goal of this project is to develop an understanding of interpopulation and interannual variation in several early life history characteristics of naturally-produced chinook salmon from the Grande Ronde and Imnaha River subbasins. This project provides information useful in the recovery of listed Snake River spring/summer chinook salmon. Specific populations included in the study are (1) Catherine Creek, (2) upper Grande Ronde River, (3) Lostine River, (4) Imnaha River, (5) Wenaha River, and (6) Minam River. In this document, we present findings from research completed in 1996. Naturally-produced chinook salmon populations in the Grande Ronde and Imnaha River subbasins have declined drastically in recent years due in part to habitat alterations and hydropower development. Declines have continued despite extensive mitigation efforts, including fish passage improvements, artificial production, supplementation, and habitat modification (BPA Division of Fish and Wildlife 1990). Snake River spring/summer chinook salmon (hereafter referred to as chinook salmon), which include naturally-produced chinook salmon in the Grande Ronde and Imnaha River subbasins, have been listed under the Endangered Species Act of 1973 as threatened or endangered since 1992.