Program in Ecological Physiology
Capability/Technical Service - Evaluation of natural rearing practices on hatchery fish physiology and ecology.
Definition. Given the apparent untenable status of many wild Pacific salmon populations, the role of hatchery stocks as a conservation tool has been increasingly debated. Numerous reviews of hatchery practices have recommended new practices concerning everything from release strategies to feeding methods that might improve the performance, especially survival to return as adult spawners, of fish produced from NFH programs.
Physiological Markers Related to Smolting and Precocious Maturation in Hatchery Steelhead
A significant proportion of steelhead released from Northwest hatcheries fails to migrate to the ocean (smolts) and instead remain in freshwater (residents) to either smolt at a later age or undergo early maturation. These resident fish can negatively impact wild fish as well as reduce the effectiveness of the hatchery program. The goal of this project is to identify physiological differences between hatchery fish which migrate to the ocean (smolts) and fish that remain in the natal stream as freshwater residents. These differences will provide an insight into the factors present in the hatchery environment that promote freshwater residency following hatchery release. After the spring 2007 hatchery steelhead release, juvenile hatchery migrants were collected at the mouth of Abernathy Creek as they emigrated out of the basin. Resident hatchery fish were sampled in Abernathy Creek near the hatchery in June, July and August. We are currently analyzing data and conducting laboratory analyses to identify physiological differences between migrant and resident fish. We will compare the sex ratio, physiology, size distribution, and level of gonadal maturation between migrant and resident hatchery juveniles.
Partner Bonneville Power Administration
Manipulating Juvenile Steelhead Growth to Reduce Competition and Encourage Smolting
Released hatchery fish are often larger than natural counterparts. Thus hatchery fish may exhibit competitive advantages over native fish. Reductions in fish size may result in less body fat that may in turn shut off cues for smoltification. Thus, it is important to reduce hatchery fish size yet produce smolts that emigrate after their release. A study has been designed and is currently ongoing to examine if hatchery steelhead growth rates can be decreased so as to reduce potential intraspecific competition with native steelhead and yet still produce smolts within one year. Steelhead are feed one of three food rations during hatchery rearing (i.e. standard ration throughout rearing, half standard ration until smolt development begins, and half standard ration until release). At release, data on fish size, body composition, and osmoregulatory indicators (for example, Na+K ATPase) for smoltification were collected.
Partner Bonneville Power Administration
The Utility of Volitional Release Strategies at Winthrop National Fish Hatchery, Winthrop, WA
One criticism of hatchery programs is that they release juvenile fish which are not fully ready to undergo downstream migration, this can lead to low post release survival and increased levels of precocious maturation in juvenile fish. The study objective is to determine if the use of volitional release for NFH juvenile fish results in the release of more physiologically and behaviorally competent smolts. The steelhead production program at Winthrop NFH was chosen as a case study. Volitionally released juvenile steelhead were compared to force released and non-migrating individuals. Factors compared include smolt physiology, reproductive physiology, and migratory behavior (using PIT tag monitoring technology). A manuscript has been submitted and accepted for publication by a peer reviewed journal.
Partner USFWS Winthrop NFH
Publication: W. L. Gale, C. R. Pasley, B. M. Kennedy, and K. G. Ostrand. In press. Juvenile steelhead release strategies: a comparison of volitional and forced release practices. North American Journal of Aquaculture.