Quote:
When the native adults return a tiny tissue sample can be taken to develop the native fishes' genetic profile. In the case of the Skagit River juvenile pre-smolt steelhead were collected from the mainstem and several tributaries and compared to the profiles of Chambers Creek hatchery-origin, winter-run steelhead. The results indicated there was virtually no survival of Chamber's Cr winter-run steelhead progeny in the Skagit River.


versus

Quote:
Up to 80% of the naturally produced steelhead in any given year were hatchery/wild hybrids. Regression model selection analysis showed that the proportion of hatchery ancestry smolts was lower in years when stream discharge was high, suggesting a negative effect of flow on reproductive success of early-spawning hatchery fish. Furthermore, proportions of hybrid smolts and adults were higher in years when the number of naturally spawning hatchery-produced adults was higher.


The Skagit experience really does NOT address hybrids... only that there was virtually no natural production of returning adult spawners from Chambers-origin parents.

The Willapa study looked at naturally produced (gravel-borne) smolts and found a significant proportion of H/W hybrids. They also observed some H/W hybrids in the returning adults. I saw no mention of H/H adult recruitment.


Edited by eyeFISH (03/04/12 03:08 PM)
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The Keen Eye MD
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