Examining the Effects of Juvenile Migration Timing on Adult Age of Columbia River Salmon Benjamin P. Sandford Fish Ecology Division Fish Ecology Division Northwest Fisheries Science Center NOAA Fisheries Service

Introduction The Columbia/Snake River System has been extensively altered with hydropower and water-storage dams. This has significantly altered salmon migration timing patterns for many reasons. Understanding the effects of these changes is important for making future management actions.

Objectives Characterize the relationship between Year- Of-Return (YOR) probability and various juvenile migration factors for wild yearling Chinook salmon –Barge transport or In-river migration separately –Within-year Bonneville passage date –Migration year –PDO, temperature, and other ocean conditions –Fish length

Methods

Dataset Wild yearling spring/summer Chinook salmon PIT- tagged at or above Lower Granite Dam: Only used years with a “reasonable number” of adult returns to Lower Granite Dam. This necessitated analyzing barge transport separately from in-river migration

YOR Model – Ordinal Logistic Regression

Analysis Ordinal Logistic Regression Fit all pertinent models (year, day, daysq, ints) Compare using Akaike’s QAICc Plot best model fits

Results

In-riverTransported YearSmoltsAdult Returns LGRLGSLMNAdult Returns Wild Snake River PIT-tagged Yearling Chinook Salmon

In-river Migration MigrationReturn Year Percent Year of Return YearY1Y2Y3TotalY1Y2Y3SAR

Wild Yearling Chinook – In-river

Wild Snake River PIT-tagged Yearling Chinook Salmon Barge Transport MigrationReturn Year Percent Year of Return YearY1Y2Y3TotalY1Y2Y3SAR

Wild Yearling Chinook – Transported

Yearling Chinook – In-river

From Peterson et al on NOAA Fisheries NWFSC site: ecinhome.cfm

Summary The age of adult return (by year) of wild yearling Chinook salmon increased for later migrants, both in- river and transported. There was substantial annual variability in age distribution and relationship to migration timing. There was little evidence that fish length (at tagging at dams) explained these results, but this needs more investigation along with ocean conditions. It takes a very large number of PIT-tagged individuals to make these assessments!

Thanks! Mark Scheuerell and Rich Zabel COE and BPA Many PIT-tag coordinators and taggers, especially Doug Marsh and CSS staff

Questions

Wild Yearling Chinook – In-river

Wild Yearling Chinook – Transported