Reproductive Viability Assessment of Reconditioned Upper-Snake River Tributary “B-Run” Female Steelhead (Oncorhynchus mykiss) Kelts

Post-spawn female steelhead (kelt) reconditioning has emerged as a recovery tool for upper-Snake River tributaries, where ESA-listed large-bodied “B-run” steelhead abundance is declining. Kelt reconditioning capitalizes on the iteroparous life history of steelhead by capturing and feeding kelts and releasing reconditioned fish to spawn naturally. To quantify the benefit of kelt reconditioning, the reproductive performance of reconditioned kelts requires assessment. Steelhead were captured and reconditioned upon return to Dworshak National Fish Hatchery (DNFH), a model for Clearwater River B-run steelhead. Reproductive development was monitored and egg quality assessed. 23% surviving kelts re-matured after one (consecutive) year of reconditioning.  Plasma estradiol levels were elevated in re-maturing versus non-re-maturing fish in summer (Aug-9: 11,585pg/ml vs. 132pg/ml) and fall (Sept-30: 20,971pg/ml vs. 249pg/ml). Consecutive spawning steelhead spawned median 1.5 weeks earlier than their initial spawning date. Fecundity and fertility in consecutive spawning reconditioned kelts and first-time (maiden) spawners returning to DNFH were compared (kelts: 6862 eggs, 91%; maidens: 6188 eggs, 84%), with results to date indicating no significant difference. Results suggest that artificial reconditioning does not compromise reproductive potential. Further work will track maturation rate and reproductive performance of alternate-year repeat spawners and directly compare individual reproductive performance in maiden and repeat spawnings.