Douglas M. Marsh

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

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...

Post-Hydropower System Delayed Mortality of Transported Snake River Stream-Type Chinook Salmon: Unraveling the Mystery

Abstract Past research indicates that on an annual basis, smolts of stream-type Chinook salmon Oncorhynchus tshawytscha collected at Snake River dams and transported by barge to below Bonneville Dam have greater post-hydropower system mortality than smolts that migrate in-river. To date, this difference has most commonly been attributed to stress from collection and transportation, leading to decreased disease resistance or predator avoidance ability. Using both hatchery and wild passive integrated transponder (PIT) tagged Chinook salmon, we explored two mechanisms that either separately or jointly contributed to an alternative explanation: Altered timing of ocean entry and lost growth opportunity leading to size-selective predation. Based on weekly estimates of in-river survival and adult return rates of smolts that were transported or that migrated in-river between Lower Granite and Bonneville dams, we found greater post-hydropower system mortality for smolts transported early in the season but greater ...

Diversion of Salmonid Smolts Tagged with Passive Integrated Transponders from an Untagged Population Passing through a Juvenile Collection System

Abstract We evaluated a system to divert salmonid smolts tagged with passive integrated transponders (PIT) from the general migrant population as they passed through a juvenile collection system at a hydroelectric dam on the Snake River. Our goal was to maximize the diversion of PIT-tagged fish while simultaneously minimizing the diversion of untagged fish. The slide-gate system that was tested diverted 81% of PIT-tagged fish detected. The number of untagged fish entering the diversion system with every PIT-tagged fish was proportional to fish abundance and averaged one untagged fish for every PIT-tagged fish. Measures of descaling, injury, and mortality for all fish in the diversion system were similar to those for fish that were not diverted. These results established our basic PIT-tag diversion system as a major tool for conducting research on Snake River anadromous salmonids.

Monitoring the Migrations of Wild Snake River Spring and Summer Chinook Salmon Smolts, 1992 Annual Report.

We PIT tagged wild spring and summer chinook salmon parr in the Snake River Basin in 1991, and subsequently monitored these fish during their smolt migration through Lower Granite, Little Goose, and McNary Dams during spring and summer 1992. This report details our findings.