Reproductive Development in Captive Reconditioned Female Steelhead Kelts: Evidence for Consecutive and Skip Spawning Life Histories
Reconditioning of post-spawned anadromous rainbow trout (steelhead kelts, Oncorhynchus mykiss) is being implemented as a recovery tool on the Yakima River in the mid-Columbia River Basin. We assessed reproductive development in female Yakima River kelts by measuring plasma estradiol-17β (E2) and vitellogenin (VG) levels during reconditioning in 2009-2011. Plasma E2 and VG levels showed fish separated into rematuring (consecutive spawning) and non-rematuring (presumed skip spawning) cohorts by October. Rematuration rates varied from 25% to 65%. Rematuring fish were consistently detected migrating toward spawning areas after release, whereas non-rematuring fish were occasionally detected on spawning migrations the following year. Rematuring fish grew more rapidly than non-rematuring fish over the reconditioning period and had higher muscle lipid levels and condition factor in October. Plasma E2 was elevated in rematuring fish by June to July, whereas plasma VG was elevated by June to August, suggesting that maturation decisions occur early in reconditioning. Rematuring and non-rematuring females could be separated by plasma E2 and VG levels by August to September, enabling separate management of consecutive and presumed skip spawners.
Pierce, A.L., J.W. Blodgett, T.D. Cavileer, L.R. Medeiros, J. Boyce, L.K. Caldwell, W.J. Bosch, R. Branstetter, D.E. Fast, D.R. Hatch, and J.J. Nagler. 2016. Reproductive development in captive reconditioned female steelhead kelts: evidence for consecutive and skip spawning life histories. Canadian Journal of Fisheries and Aquatic Sciences 74(7):1049-1060. Online at https://doi.org/10.1139/cjfas-2016-0065.