Evaluating Reproductive Success of Maiden and Kelt Steelhead Spawners in a Hatchery Setting

Reproductive success is difficult to observe in the field, particularly for steelhead.  The operation of weirs and traps are often compromised by spring-time flow regimes, and rarely catch a large proportion of the spawning population.  These logistical issues of collection and documentation compounded by the complexity of Oncorhynchus mykiss life history and other environmental variables has limited the success of obtaining easily quantifiable results regarding steelhead kelt spawner contribution.  For these reasons, we are investigating gamete and progeny viability of reconditioned kelt steelhead in a hatchery setting.   Hatchery-origin prespawn adults were collected at the Powerdale trap located on the Hood River, a tributary of the Columbia River.  The female fish were air spawned and the eggs fertilized with cryopreserved milt.   Offspring are raised for several weeks while recording basic growth characteristics.  The surviving spawners are reconditioned using techniques learned from the steelhead kelt reconditioning experiment at Prosser, WA and spawned the following year or the year after (skip year spawning), utilizing the same cryopreserved milt from the same males.  The kelts, when compared against their maiden spawning year, increased in egg production, egg fertilization, and progeny survival.  We also compared the long-term reconditioning kelts against the incoming maiden brood.   The kelts on average performed as well or better than the best maiden spawners in egg and progeny performance categories.  Kelt spawners produced on average an additional 1500 more eggs than maiden spawners. Fertilization success rates for maiden and kelt spawners were not significantly different.   Juvenile survival on average was slightly higher for kelt progeny.  This study is currently ongoing and given that these results are limited, they are still encouraging, in that it appears that steelhead kelts are important and vital contributing members to steelhead populations in the Columbia River Basin.  This data also suggests that kelt reconditioning may be a used to bolster or increase this naturally occurring life history towards the betterment of depressed steelhead populations throughout the basin.