Steelhead Research

Science paper about negative hatchery breeding impact in hood river steelhead. The power and fine resolution of this research is because they identified every single return individual and their pedigree. A fine research and elegant design, but sad story of the steelhead.
Title: Genetic Effects of Captive Breeding Cause a Rapid, Cumulative Fitness Decline in the Wild by Hitoshi Araki,* Becky Cooper, Michael S. Blouin Science 5 October 2007: Vol. 318. no. 5847, pp. 100 - 103

Captive breeding is used to supplement populations of many species that are declining in the wild. The suitability of and long-term species survival from such programs remain largely untested, however. We measured lifetime reproductive success of the first two generations of steelhead trout that were reared in captivity and bred in the wild after they were released. By reconstructing a three-generation pedigree with microsatellite markers, we show that genetic effects of domestication reduce subsequent reproductive capabilities by ~40% per captive-reared generation when fish are moved to natural environments. These results suggest that even a few generations of domestication may have negative effects on natural reproduction in the wild and that the repeated use of captive-reared parents to supplement wild populations should be carefully reconsidered.

Why Artificial Breeding Is not Good...

A recent report in Atlantic salmon.
Mate choice play a role in genetic diversity and parasite resistance.


Title: MHC-mediated mate choice increases parasite resistance in salmon
Proceedings of the Royal Society B. Volume 275, Number 1641 / June 22, 2008
Natural (parasite-driven) and sexual selection are thought to maintain high polymorphism in the genes of the major histocompatibility complex (MHC), but support for a link between mate choice, MHC variation and increased parasite resistance is circumstantial. We compared MHC diversity and Anisakis loads among anadromous Atlantic salmon (Salmo salar L.) returning to four rivers to spawn, which had originated from natural spawning (parents allowed to mate freely) or artificial crosses (parents deprived from the potential benefits of mate choice). We found that the offspring of artificially bred salmon had higher parasite loads and were almost four times more likely to be infected than free-mating salmon, despite having similar levels of MHC diversity. Moreover, the offspring of wild salmon were more MHC dissimilar than the offspring of artificially crossed salmon, and uninfected fish were more dissimilar for MHC than infected fish. Thus, our results suggest a link between disassortative mating and offspring benefits and indicate that MHC-mediated mate choice and natural (parasite-driven) selection act in combination to maintain MHC diversity, and hence fitness. Therefore, artificial breeding programmes that negate the potential genetic benefits of mate choice may result in inherently inferior offspring, regardless of population size, rearing conditions or genetic diversity.

be salmon