Spawning Migrations of American Shad in the Columbia River

We sampled American shad, Alosa sapidissima, in the Columbia and Snake Rivers during 2005-2007 & 2010 to characterize basic migration biology of the population, as a model system to test general migration ecology hypotheses, and to determine if dam passage metrics for shad in the Columbia River are better than those for eastern United States populations, which are imperiled.  We PIT-tagged and released 2496 adults during the 2005-2007 study period.  We simultaneously determined length, mass, sex, age and spawning history (from scales) and energetic status (using a Fatmeter) for a subset of PIT tagged fish in an effort to relate individual traits to migration behavior.  Collections of adults at Bonneville and Lower Granite dams and of juveniles at six lower Columbia and Snake river dams characterized seasonal and longitudinal patterns during upstream and downstream migration, respectively.  Analyses demonstrated that: 1) individual adults returned to the Columbia Basin spawn in multiple years; 2) the adult populations at Lower Granite Dam (rkm 695) were younger and male-biased compared to adults at Bonneville Dam (rkm 235); 3) that mean initial lipid content of adults detected at McNary Dam (rkm 470) was higher than adults detected only at Bonneville Dam; and 4) juvenile growth rates were higher in upstream reaches of the basin, particularly in the Snake River reservoirs.  In 2010, we radio- and PIT-tagged 234 adult fish to estimate individual passage behavior and success at the four lower Columbia River dams.  A total of 26% of the tagged fish passed Bonneville Dam.  A total of 78% of the fish passing Bonneville Dam passed The Dalles Dam, 45% of those passed John Day Dam, and 48% of those passed McNary Dam.  A seasonal effect was evident, with 57% of the fish tagged in the early part of the run passing Bonneville Dam, compared to 18 and 4% during the middle and late parts of the run.  Collectively, the results suggest that: 1) shad passage behavior and performance at dams differ from salmonids; 2) that adult upstream migration behavior appears to be relatively flexible, may be dependent on life history stage and/or initial condition of individuals, and may affect offspring growth and survival; 3) the ecological effects of adults in reservoirs differs longitudinally; and 4) indicate greater passage success than observed in East Coast rivers.