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

Masu Salmon in Hokkaido

Snake river Cutthroat Trout

It's a self-explaning species...as you can tell the red-orange marking on the throat... the cutthroat trout. What a beautiful trout species... not only the brillient red marking stikes me, but also the redish - translucent fin are extremely attractive. To my knowledge no one has study the read marking to the cutthoat trout, what is the function? what is the pigment? I have no clue. Maybe I should plan a long vacation in the smoky mountain region and observe this species more closely : )

Atlantic Salmon's Feeding Competition

You don't need to be big, but you need to be there earlier!
From a recent scientific research: The relative influence of prior residency and dominance on the early feeding behaviour of juvenile Atlantic salmon: Animal Behaviour 2003 65 (6) 1141-1149
"In many species where social hierarchy mediates conflict over resources, dominant individuals monopolize food, shelter and reproductive opportunities. The benefits of social dominance, however, can often be offset by a prior residence advantage, whereby individuals arriving first in a new habitat obtain, and subsequently defend, the most profitable sites. We investigated the relative influence of these two factors on the acquisition of feeding territories by juvenile Atlantic salmon,Salmo salar L., by placing groups of six individuals of known dominance rank sequentially into an experimental arena with feeding sites of varying quality. Dominants had an advantage over subordinates in the percentage of time spent in a good-quality feeding site and individual feeding rate. There was also a significant time of arrival effect: those individuals that arrived first in a habitat monopolized the resource. The two effects were of approximately equal strength, so that late-arriving dominant fish had similar success as prior resident subordinates..."

Brook Trout in the Western US Rivers

This brook trout was caught in the western united state, Wyoming. Although this beautiful little trout is gorgeous in their coloration and is a perfect match for a small fly rod. The appearance of him is not a good sign for the local ecosystem, regard to the preservation of biodiversity. Invasive species is what a conservationist call them - brook trout in the west, as well as the brown trout in the whole US, whole south hemisphere (no native trout in the south). Historically, the brook trout only distributed in the eastern part of the US. Started from the south of Appalachia range of Northern Georgia all the way through Great smoky mountain, Maine into Canada. There are also another sea run form of brook trout still thriving in the upper northeast....(to be continued...)