Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 9121
Title: Characterizing migration and survival between the upper Salmon River Basin and Lower Granite Dam for juvenile Snake River sockeye salmon, 2011-2014
Author/Editor: Gordon A. Axel, Christine C. Kozfkay, Benjamin P. Sandford, Michael Peterson, Matthew G. Nesbit, Brian J. Burke, Kinsey E. Frick, Jesse J. Lamb
Publication Year: 2017
Publisher: National Marine Fisheries Service and Idaho Department of Fish and Game
Contracting Agency: Bonneville Power Administration. Portland, Oregon
Keywords: sockeye salmon, smolt survival, Snake River Basin, radio telemetry, passive integrated transponder (PIT),

During spring 2011-2014, we tagged and released groups of juvenile hatchery Snake River sockeye salmon Oncorhynchus nerka to Redfish Lake Creek in the upper Salmon River Basin.  These releases were part of a coordinated study to characterize migration and survival of juvenile sockeye to Lower Granite Dam.  We estimated detection probability, survival, and travel time based on detections of fish tagged with either a passive integrated transponder (PIT) or both a radio transmitter and PIT tag.  Passage metrics were then compared between cohorts of fish from Sawtooth vs. Oxbow Fish Hatcheries and between fish released during daytime vs. nighttime periods.

For PIT tagged study fish in 2011, estimated survival from release to Lower Granite Dam was 72.8% for Sawtooth and 77.1% for Oxbow groups.  These were among the highest estimates of survival since the sockeye salmon captive broodstock program began 16 years ago.  However, for study fish with radio tags in 2011, survival to Lower Granite Dam was only 14.2% based on estimates derived from radio-tag detections.

We modified tagging protocols to allow fish to acclimate to climate and to provide a longer period of post-tagging observation.  However, in the remaining study years, from 2012 to 2014, estimated survival to Lower Granite Dam remained lower for radio tagged fish from both hatcheries, ranging 3.6 51.8% for radio vs. 50.5 69.4% for PIT tag groups.

Because both tag groups experienced similar passage conditions, but mortality was higher for radio tagged groups, we inferred that mortality related to a radio tag effect likely developed as a factor that influenced survival.  For yearling Chinook salmon, previous research has shown significant differences in survival between radio and PIT tagged groups that traveled further than 225 km or had travel times in excess of 6 d.  Our study groups traveled approximately 750 km over a period of 7 10 d. Thus, mortality associated with tag effects was a likely contributor to the lower estimated survival to Lower Granite Dam for fish with radio tags.

Despite the limitations associated with radio tags over longer distances, these tags were useful in identifying study reaches where fish experience high rates of mortality, an important objective of our study.  Radio tag data indicated two reaches in particular where estimated survival was lower for daytime and nighttime release groups and for releases from both hatcheries across all three years.  The first of these reaches was between the release site and the Salmon River at its confluence with Valley Creek, about 9 rkm downstream from the release site.  The second was at the confluence of the Salmon and North Fork Salmon Rivers, about 238 rkm downstream from release.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.