Comparing the Reproductive Success of Yakima River Hatchery- and Wild-Origin Spring Chinook; Yakima/Klickitat Fisheries Project Monitoring and Evaluation, 2004-2005 Annual Report.
- Washington Department of Fish and Wildlife, Olympia, WA
- Oncorh Consulting, Olympia, WA
A growing body of literature suggests that adult salmon produced by artificial culture are not as reproductively successful as wild fish when they spawn under natural conditions. Behavioral, morphological, and physiological divergences have been observed between hatchery and wild fish. These disparities are the likely proximate causes of the differences seen in the reproductive success of hatchery and wild salmonids. Two evolutionary paradigms have been proposed to explain why salmonids cultured in hatcheries are genetically and phenotypically different from wild cohorts. The first proposes that natural selection has been significantly relaxed in hatcheries. Consequently, fish that normally would have perished because of the possession of unsuitable traits are able to survive. If these traits have a genetic basis, they may become established in a hatchery population and cause its productivity to be less than expected if the fish are once again exposed to natural selection pressures. The second theorizes that environmental and social conditions in hatcheries are less variable than in the natural environment and that these conditions will remain relatively constant from one generation to the next. In this circumstance, selection for genetic traits that adapt fish to artificial culture will become prevalent in the population. Such traits may be mal-adaptive under natural conditions. Many of the studies that have compared the reproductive success (RS) of hatchery and wild fish, however, have used non-local hatchery fish that have experienced multiple generations of hatchery culture. Few efforts have been made where both the hatchery and wild fish have originated from the same population. When such studies have been performed differences in the competency of the fish to produce offspring have not been detected or are not as great as those expressed when non-local hatchery fish have been used. The hatchery spring Chinook produced by the Yakima Fisheries Project originated from wild fish returning to the upper Yakima River. When they return as adults, almost all of them will spawn naturally in the Yakima River. The offspring they produce are expected to augment the Yakima spring Chinook population. Whether such an increase will occur or how great it may be depends on two factors, the ability of hatchery fish to reproduce under natural conditions and the capacity of their offspring to survive to maturity. One of the objectives of the Yakima Fisheries Project is to determine whether the hatchery-origin adults produced by the project have experienced any reduction in their ability to reproduce under natural conditions. To accomplish that objective an observation stream was built in 2000 on the grounds of the Cle Elum Supplementation and Research Facility. Beginning in 2001 hatchery and wild spring Chinook from the upper Yakima River stock have been introduced into the stream and allowed to reproduce. Microsatellite DNA is used to establish the genetic relationships between the adults placed into the stream and fry that are produced by each population. Six populations consisting of mixtures of wild and hatchery fish have been placed into the stream. Pedigree assessments have been completed on five of them. These assessments have shown that the reproductive success in males is often twice as variable as that experienced by females. In the five populations so far examined; wild males (age 4 and 5) produced the most offspring. The success of comparable hatchery males relative to wild males ranged from 37% to 113%. Hatchery and wild males maturing as 3-yr-olds (jacks) and as 1- and 0-yr-olds (precocious males) were also used in the study populations. They were not as successful at producing offspring as the larger hatchery and wild males. During 2001 and 2002 two populations of hatchery and wild fish were placed into the observation stream each year. Each one occupied about half of the structure. In these populations wild females exhibited a superior capacity to deposit eggs. In addition, their eggs survived to the fry stage at higher rates. This survival advantage ranged from 1.9 to 11.7%. In 2003 the entire observation stream was made available to a single population of fish in an effort to reduce intrasexual competition among the females for redd locations. In this year, hatchery females were better at depositing eggs (12.5%) and their buried eggs also achieved a higher egg-to-fry survival rate (3.4%). This suggests that at low population levels hatchery females were as competent as wild fish in burying eggs and in producing fry. Although variation in the reproductive success of females was lower than that seen in males it could be quite variable. For example, coefficient of variation values calculated on female RS ranged from 34 to 77% in the populations we examined. Numerous factors may affect RS in females.
- Research Organization:
- Bonneville Power Administration (BPA), Portland, OR (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- 00017478
- OSTI ID:
- 887233
- Report Number(s):
- DOE/BP-00017478-6; R&D Project: 199506325; TRN: US200617%%616
- Country of Publication:
- United States
- Language:
- English
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