Use of Passive Integrated Transponder (PIT) Tags to Monitor Migration Timing of Snake River Chinook Salmon Smolts

Abstract

Abstract Before 1989, there was little detailed knowledge of the migrational timing of wild smolts of Snake River spring and summer chinook salmon Oncorhynchus tshawytscha from individual streams. With the development of the passive integrated transponder (PIT) tag and methods for collecting and tagging parr, acquisition of information on migrational timing became feasible. We PIT-tagged wild chinook salmon parr in several streams in Idaho and Oregon each summer from 1988 through 1990. Each subsequent spring and summer, we detected surviving smolts on their migration through Lower Granite Dam. We also PIT-tagged hatchery-reared parr during fall or late winter and compared their migrations with those of wild fish. Migrational timing of wild smolts through Lower Granite Dam varied for fish from different streams and also differed from hatchery-reared fish. Generally, wild spring chinook salmon migrated later and over a more protracted period than their hatchery-reared counterparts. Wild summer chinook salmo...