Reproductive Development in Reconditioned Female Yakima River Steelhead Kelts: Evidence for Consecutive and Skip Repeat Spawning Life Histories

Columbia River Basin steelhead are capable of iteroparity, however, repeat spawning rates are low.  Projects to capture and recondition ESA-listed downstream migrating kelts are underway, with the goal of releasing rematuring fish into rivers to spawn naturally.  Ocean-reconditioned repeat spawners may return after a single summer in the ocean (consecutive spawners), or after two summers (skip spawners).  To determine whether the consecutive and skip spawning life histories are found in captive-reconditioned steelhead, we measured blood levels of vitellogenin and estradiol in kelts in the reconditioning program at Prosser, Washington, 2009-2013.  Estradiol and vitellogenin levels separated rematuring and non-rematuring females at release in October.  On average, 57% of fish were rematuring at release. Vitellogenin was elevated in rematuring fish by mid-August, whereas estradiol was elevated by mid-July.  Rematuring fish grew more rapidly over the reconditioning period and had higher muscle lipid levels at release than non-rematuring fish, suggesting that rematuration is associated with positive energetic status.  Data comparing blood hormone levels in rematuring reconditioned kelts and maiden spawners will be presented.  This study shows that the consecutive and skip spawning life histories are found in reconditioned steelhead kelts.  Strategies to allow skip spawners to contribute to target populations should be developed.