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I got my hands on this interesting new report out entitled; Naturally Spawning Hatchery Steelhead Contribute to Smolt Production but Experience Low Reproductive Success
Unfortunately it is in the pdf format so I can’t copy/paste any or all of it but will attempt to type out the abstract for the article and offer to email the complete 10 page report to anyone interested in reading it.
The article is regarding Clackamas River hatchery summer and hatchery winter steelhead and Clackamas wild winter steelhead . All three were genetically tested along with out-migrating smolts. I find the results very interesting and of no surprise with the exception of the surprising success of the hatchery summers to spawn in the wild. As it turns out this was not a good thing.
Here’s the abstract:
“We used genetic mixture analyses to show that hatchery summer-run steelhead Oncorhynchus mykiss, an introduced life history in the Clackamas basin of Oregon, where only winter-run steelhead are native, contributed to the naturally produced smolts out-migrating from the basin. Hatchery-produced summer steelhead smolts were released starting in 1971, and returning adults were passed above a dam into the upper Clackamas River until 1999. In the two years of our study, summer steelhead adults, mostly hatchery fish, made up 60% to 82% of the natural spawners in the river. Genetic results provided evidence that interbreeding between hatchery summer and wild winter steelhead was likely minor. Hatchery summer steelhead reproductive success was relatively poor. We estimated that they produced only about one-third the number of smolts per parent that wild winter steelhead produced. However, the proportions of summer natural smolts were large (36-53% of the total naturally produced smolts in the basin) because hatchery adults predominated on the spawning grounds during our study. Very few natural-origin summer adults were observed, suggesting high mortality of the naturally produced smolts following emigration. Counts at the dam demonstrated that hatchery summer steelhead predominated on natural spawning grounds throughout the 24-year hatchery program. Our data support a conclusion that hatchery summer steelhead adults and their offspring contribute to wild winter steelhead population declines through competition for spawning and rearing habitats”.
So what I find interesting about this report is that both hatchery and wild strains of steelhead adults and smolts were identified through genetic testing. It appears that the summers were more successful at spawning in the wild than previously thought. The progeny of these naturally spawning summer hatchery fish had poor survival rates in the wild (which is consistent with science). The slightly earlier spawning summer hatchery steelhead were using up the limited natural spawning grounds and rearing habitat with no positive results for the naturally spawning summers and at the same time contributed to the decline of the Clackamas native winter steelhead.
Anyone wanting the report email me and I will attach the 10 page report and send to you as a reply. If you think hatchery fish are good and without detrimental effects to wild fish I would recommend you read this report. :wink:
Here’s a few items I found interesting in the report:
“Very few un-unmarked summer steelhead were ever observed in the Clackamas River, either at the dam or in the fishery, indicating poor reproduction by or survival of the hatchery fish passed upstream”.
“Risk to wild winter steelhead from the hatchery summer steelhead program were assumed to be very low”.
“A decline in Clackamas River wild winter steelhead abundance occurred in the 1990’s (Chilcote 1998) and caused a more careful consideration of factors affecting the population, including the hatchery summer steelhead program. We hypothesized that hatchery summer steelhead were successfully spawning and producing juvenile offspring that largely died before reaching adulthood.
If this were so, hatchery summer adults and their offspring could have been occupying substantial amounts of winter steelhead spawning and rearing habitat and contributing to wild winter steelhead declines through competition”.
“Thus, summer steelhead may be expected tp emerge earlier and occupy choice feeding territories before wild winter steelhead, which may place winter steelhead at a particular disadvantage”.
“To evaluate potential effects of the hatchery summer steelhead program on wild winter steelhead, we had to address two issues: (1) whether hatchery summer steelhead were spawning naturally and producing smolts and (2) whether the summersteelhead produced had any effects on the productivity of wild winter steelhead”.
“We collected out-migrating smolts, identified as naturally produced based on lack of adipose fin clip marks, at the North Fork Dam downstream migrant trap during the peak of steelhead out-migration from 12 to 15 May…”.
“All allozyme analyses for this study was conducted at WDFW Genetics Laboratory”.
“The second model assumed that smolts resulted largely from assortative mating, in which the three parent stocks bred only within their own group and did not hybridize”.
“Contributions to smolts from hatchery winter stock were minor and imprecise according to both models”.
“Admixture analysis, which assumed interbreeding among stocks, indicated that hatchery summer steelhead made the largest contribution to 1995 smolts, followed by wild winter steelhead (Table 3)”.
“However, it was apparent from both models that hatchery summer steelhead contributed at relatively high levels to natural production of smolts in both years”.
DISCUSSION
“We found that hatchery summer steelhead contributed substantially to natural smolt production according to both of our models of stock interbreeding. The previous assumption that hatchery summer steelhead did not spawn successfully had to be dismissed, …”
“summer and winter steelhead maintain reproductive isolation through run and spawn-timing differences and seasonal migration barriers within a drainage”.
“Wild winter steelhead genetic differentiation indicated that this population has not been homogenized by interbreeding with hatchery stocks. These data support the hypothesis that among-stock reproductive isolation is relatively high”.
“This successful allocation of most smolts to a single parent source by mixed-stock MLE analysis gave us confidence that interbreeding among winter and summer steelhead was at very low levels”.
“Whatever interbreeding may have occurred between hatchery and wild fish, it has not diminished the genetic and biological distinctiveness of the wild winter steelhead population, and we do not believe it has had an effect on the productivity of the wild population. The decline in wild winter steelhead abundance was not likely due to diminished reproductive success of a greatly hybridized population”.
“Hatchery summer steelhead were able to produce smolt offspring, but they did so with much less success than wild winter steelhead. In the two years of this study hatchery summer steelhead produced about a third or less as many smolts per parent and about a tenth or less as many adult offspring per parent as wild winter steelhead did”.
“We conclude that even though naturally spawning hatchery steelhead may experience poor reproductive success, they and their juvenile progeny may be abundant enough to occupy substantial portions of spawning and rearing habitat to the detriment of wild fish populations. The capacity of the Clackamas basin to produce steelhead smolts is expected to be finite (Allen 1969). Therefore, the large numbers of introduced summer steelhead would have competed heavily with wild winter steelhead for habitat resources, and this may have contributed to their decline”.
“In the Clackamas basin, smolt offspring of hatchery fish appear to have wasted the production from natural habitat because very few survived to return as adults”.
“Evidence of success must also include returning adult offspring and no depression of wild fish productivity”.
“Supplementation programs should be attuned to basin carrying capacities so that they do not reduce wild fish productivity through competition for resources”.
Geez, maybe I should have typed up the whole report! :grin:
Anyway, there is a lot more to the report including a lot of interesting specifics and all the boring scientific stuff I left out like; (p<0.05), ALAT* and PGK-2; and LDH-B2*, etc, etc.
Dan
Unfortunately it is in the pdf format so I can’t copy/paste any or all of it but will attempt to type out the abstract for the article and offer to email the complete 10 page report to anyone interested in reading it.
The article is regarding Clackamas River hatchery summer and hatchery winter steelhead and Clackamas wild winter steelhead . All three were genetically tested along with out-migrating smolts. I find the results very interesting and of no surprise with the exception of the surprising success of the hatchery summers to spawn in the wild. As it turns out this was not a good thing.
Here’s the abstract:
“We used genetic mixture analyses to show that hatchery summer-run steelhead Oncorhynchus mykiss, an introduced life history in the Clackamas basin of Oregon, where only winter-run steelhead are native, contributed to the naturally produced smolts out-migrating from the basin. Hatchery-produced summer steelhead smolts were released starting in 1971, and returning adults were passed above a dam into the upper Clackamas River until 1999. In the two years of our study, summer steelhead adults, mostly hatchery fish, made up 60% to 82% of the natural spawners in the river. Genetic results provided evidence that interbreeding between hatchery summer and wild winter steelhead was likely minor. Hatchery summer steelhead reproductive success was relatively poor. We estimated that they produced only about one-third the number of smolts per parent that wild winter steelhead produced. However, the proportions of summer natural smolts were large (36-53% of the total naturally produced smolts in the basin) because hatchery adults predominated on the spawning grounds during our study. Very few natural-origin summer adults were observed, suggesting high mortality of the naturally produced smolts following emigration. Counts at the dam demonstrated that hatchery summer steelhead predominated on natural spawning grounds throughout the 24-year hatchery program. Our data support a conclusion that hatchery summer steelhead adults and their offspring contribute to wild winter steelhead population declines through competition for spawning and rearing habitats”.
So what I find interesting about this report is that both hatchery and wild strains of steelhead adults and smolts were identified through genetic testing. It appears that the summers were more successful at spawning in the wild than previously thought. The progeny of these naturally spawning summer hatchery fish had poor survival rates in the wild (which is consistent with science). The slightly earlier spawning summer hatchery steelhead were using up the limited natural spawning grounds and rearing habitat with no positive results for the naturally spawning summers and at the same time contributed to the decline of the Clackamas native winter steelhead.
Anyone wanting the report email me and I will attach the 10 page report and send to you as a reply. If you think hatchery fish are good and without detrimental effects to wild fish I would recommend you read this report. :wink:
Here’s a few items I found interesting in the report:
“Very few un-unmarked summer steelhead were ever observed in the Clackamas River, either at the dam or in the fishery, indicating poor reproduction by or survival of the hatchery fish passed upstream”.
“Risk to wild winter steelhead from the hatchery summer steelhead program were assumed to be very low”.
“A decline in Clackamas River wild winter steelhead abundance occurred in the 1990’s (Chilcote 1998) and caused a more careful consideration of factors affecting the population, including the hatchery summer steelhead program. We hypothesized that hatchery summer steelhead were successfully spawning and producing juvenile offspring that largely died before reaching adulthood.
If this were so, hatchery summer adults and their offspring could have been occupying substantial amounts of winter steelhead spawning and rearing habitat and contributing to wild winter steelhead declines through competition”.
“Thus, summer steelhead may be expected tp emerge earlier and occupy choice feeding territories before wild winter steelhead, which may place winter steelhead at a particular disadvantage”.
“To evaluate potential effects of the hatchery summer steelhead program on wild winter steelhead, we had to address two issues: (1) whether hatchery summer steelhead were spawning naturally and producing smolts and (2) whether the summersteelhead produced had any effects on the productivity of wild winter steelhead”.
“We collected out-migrating smolts, identified as naturally produced based on lack of adipose fin clip marks, at the North Fork Dam downstream migrant trap during the peak of steelhead out-migration from 12 to 15 May…”.
“All allozyme analyses for this study was conducted at WDFW Genetics Laboratory”.
“The second model assumed that smolts resulted largely from assortative mating, in which the three parent stocks bred only within their own group and did not hybridize”.
“Contributions to smolts from hatchery winter stock were minor and imprecise according to both models”.
“Admixture analysis, which assumed interbreeding among stocks, indicated that hatchery summer steelhead made the largest contribution to 1995 smolts, followed by wild winter steelhead (Table 3)”.
“However, it was apparent from both models that hatchery summer steelhead contributed at relatively high levels to natural production of smolts in both years”.
DISCUSSION
“We found that hatchery summer steelhead contributed substantially to natural smolt production according to both of our models of stock interbreeding. The previous assumption that hatchery summer steelhead did not spawn successfully had to be dismissed, …”
“summer and winter steelhead maintain reproductive isolation through run and spawn-timing differences and seasonal migration barriers within a drainage”.
“Wild winter steelhead genetic differentiation indicated that this population has not been homogenized by interbreeding with hatchery stocks. These data support the hypothesis that among-stock reproductive isolation is relatively high”.
“This successful allocation of most smolts to a single parent source by mixed-stock MLE analysis gave us confidence that interbreeding among winter and summer steelhead was at very low levels”.
“Whatever interbreeding may have occurred between hatchery and wild fish, it has not diminished the genetic and biological distinctiveness of the wild winter steelhead population, and we do not believe it has had an effect on the productivity of the wild population. The decline in wild winter steelhead abundance was not likely due to diminished reproductive success of a greatly hybridized population”.
“Hatchery summer steelhead were able to produce smolt offspring, but they did so with much less success than wild winter steelhead. In the two years of this study hatchery summer steelhead produced about a third or less as many smolts per parent and about a tenth or less as many adult offspring per parent as wild winter steelhead did”.
“We conclude that even though naturally spawning hatchery steelhead may experience poor reproductive success, they and their juvenile progeny may be abundant enough to occupy substantial portions of spawning and rearing habitat to the detriment of wild fish populations. The capacity of the Clackamas basin to produce steelhead smolts is expected to be finite (Allen 1969). Therefore, the large numbers of introduced summer steelhead would have competed heavily with wild winter steelhead for habitat resources, and this may have contributed to their decline”.
“In the Clackamas basin, smolt offspring of hatchery fish appear to have wasted the production from natural habitat because very few survived to return as adults”.
“Evidence of success must also include returning adult offspring and no depression of wild fish productivity”.
“Supplementation programs should be attuned to basin carrying capacities so that they do not reduce wild fish productivity through competition for resources”.
Geez, maybe I should have typed up the whole report! :grin:
Anyway, there is a lot more to the report including a lot of interesting specifics and all the boring scientific stuff I left out like; (p<0.05), ALAT* and PGK-2; and LDH-B2*, etc, etc.
Dan