Reproductive Development, Energy Stores, and Post-Release Migration Of Reconditioned Female Steelhead Kelts In The Yakima River

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, 2009-2011.  Estradiol and vitellogenin levels separated rematuring and non-rematuring females at release in October.  Overall, 49% 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, had higher muscle lipid levels at release, and were more likely to be detected migrating upriver after release, whereas non-rematuring fish were sometimes detected on spawning migrations one year later.  This study shows that the consecutive and skip spawning life histories are found in reconditioned steelhead kelts.  Rematuration is associated with positive energetic status, and rematuring fish show a migration pattern consistent with spawning.