Harvest Characteristics of Summer Steelhead Derived from Hatchery Parents Captured by Angling in the Grande Ronde River

One of the primary objectives of the Lower Snake Compensation Plan in Oregon is to restore historical recreational and tribal fisheries for summer steelhead in the Grande Ronde river basin. The annual release of hatchery steelhead smolts in northeast Oregon streams provides hatchery adult returns that contribute to consumptive recreational fisheries on the Grande Ronde and Wallowa rivers.  In an effort to reduce adult stray rates and increase fall recreational fishery opportunities in the Lower Grande Ronde River, we created a line of F1 offspring from hatchery steelhead collected by hook and line in the Grande Ronde River in autumn (hereafter referred to as the Autumn Line).  In this study, we compared harvest contribution of the Autumn Line to standard production progeny released at the same location.  We used passive integrated transponder (PIT) tags to estimate adult migration timing, and found that Autumn Line progeny arrive at Lower Granite Dam approximately three weeks earlier than standard production fish.  We used creel survey data and coded-wire tag (CWT) recoveries from Oregon fisheries to estimate harvest timing of the two release groups.  On average, the peak harvest of Autumn Line adults in the Grande Ronde basin occurred in the month of October and represented 30% of total Autumn Line harvest. In contrast, harvest of standard production fish peaked in March of the following spring, representing 36% of total standard production harvest.  In order to compare the harvest contribution of the two release groups, we calculated a harvest index (fish harvested/fish available in the fishery) using PIT tags to estimate the abundance of CWT adults available in recreational fisheries above Lower Granite Dam.  Autumn Line adults had a higher harvest index in the months of September through January on the Lower Grande Ronde River.  The difference in harvest index was most prominent in October, when Autumn Line adults were harvested at ten times the rate of standard production adults.  Our results suggest that steelhead progeny from the Autumn Line return earlier as adults and provide a greater contribution to fall harvest in Oregon fisheries than standard production releases; thus, development of the Autumn Line has successfully enhanced the fall steelhead fishery on the Lower Grande Ronde River.