Impacts of run‐of‐river hydropower on coho salmon (
            Oncorhynchus kisutch
            ): the role of density‐dependent survival

The success of expanded salmon hatchery programs will depend strongly on the degree of density-induced diminishing returns per smolt released. Several authors have addressed the question of density-dependent mortality at sea in coho salmon (Oncorhynchus kisutch), but have come to conflicting conclusions. We believe there are compelling reasons to reinvestigate the data, and have done so for public hatchery fish, using a variety of approaches. The results provide evidence that survival of these public hatchery fish is negatively affected, directly by the number of public hatchery smolts and indirectly by the number of private hatchery smolts. These results are weak, statistically, and should be considered primarily as a caution to those who, on the basis of other published work, believe that density-dependence does not exist. The results reported here also re-emphasize the often overlooked point that inferences drawn from data are strongly biased by investigators' views of how the systems of interest work and by the statistical assumptions they make preparatory to the analysis of those data.

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Role of Instream Rootwads as Juvenile Coho Salmon (Oncorhynchus kisutch) and Steelhead Trout (O. mykiss) Cover Habitat Under Varying Streamflows

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f90-098 ◽

1990 ◽

Vol 47 (5) ◽

pp. 852-861 ◽

Cited By ~ 84

Author(s):

C. S. Shirvell

Keyword(s):

British Columbia ◽

Coho Salmon ◽

Oncorhynchus Kisutch ◽

Physical Structure ◽

Steelhead Trout ◽

Young Fish ◽

Light Intensities ◽

Salmon Fry ◽

Reduced Light

Coho salmon fry (Oncorhynchus kisutch) and steelhead parr (O. mykiss) occupied previously infrequently-used mid-channel areas of Kloiya Creek, British Columbia, Canada, once artificial rootwads were placed there. Ninetynine percent of all coho salmon fry and 83% of steelhead parr occupied positions downstream of natural or artificial rootwads during artificially created drought, normal, and flood streamflows. Fish associated with rootwads regardless of distance from shore, but steelhead parr preferred rootwads away from shore while coho salmon fry preferred rootwads next to shore. Coho salmon fry increased their use of natural rootwads where currents were slow during floods, while steelhead parr increased their use of artificial and natural rootwads where light remained low during droughts. Young fish apparently selected areas having slower water 80% of the time because they provided shelter from adverse current, and areas having reduced light intensities 20% of the time because they provided protection from predators, juvenile coho salmon and steelhead in Kloiya Creek selected locations with slower water velocities and reduced light intensities irrespective of the physical structure that caused them.

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Disruption of seasonality in growth hormone-transgenic coho salmon (Oncorhynchus kisutch) and the role of cholecystokinin in seasonal feeding behavior

Hormones and Behavior ◽

10.1016/j.yhbeh.2008.02.010 ◽

2008 ◽

Vol 54 (4) ◽

pp. 506-513 ◽

Cited By ~ 34

Author(s):

M LOHMUS ◽

P RAVEN ◽

L SUNDSTROM ◽

R DEVLIN

Keyword(s):

Growth Hormone ◽

Feeding Behavior ◽

Coho Salmon ◽

Oncorhynchus Kisutch

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Spatial distribution, survival, and growth of sibling groups of juvenile coho salmon (Oncorhynchus kisutch) in an experimental stream channel

Canadian Journal of Zoology ◽

10.1139/z94-283 ◽

1994 ◽

Vol 72 (12) ◽

pp. 2119-2123 ◽

Cited By ~ 15

Author(s):

Thomas P. Quinn ◽

Andrew H. Dittman ◽

N. Phil Peterson ◽

Eric Volk

Keyword(s):

Spatial Distribution ◽

Coho Salmon ◽

Oncorhynchus Kisutch ◽

Positive Density ◽

Stream Channel ◽

Density Dependent ◽

Intrapopulation Variation ◽

Survival And Growth ◽

Dependent Growth ◽

Sibling Recognition

The spatial distribution, survival, and growth of two full-sibling families of coho salmon (Oncorhynchus kisutch) in an experimental outdoor stream channel were compared between the families and with the performance of one of the families in an allopatric control channel after 75 d of rearing. No difference in survival was observed between families (81.2% overall), but their spatial distributions in the channel differed markedly. One family or the other numerically dominated 5 of 7 riffle-pool habitat units within the sympatric treatment channel. The family that was larger at the beginning of the experiment (0.52 vs. 0.37 g mean mass) was also larger at the end (2.03 vs. 1.58 g). While there was little evidence of density-dependent growth overall, the growth of each family was correlated with the density of siblings in the unit. However, the larger bodied family showed negative density-dependent growth, whereas the smaller bodied family showed positive density-dependent growth. These patterns of distribution and growth may have arisen from sibling recognition or some other proximate mechanism such as assortative distribution based on size or interfamily variation in aggression. Regardless of the mechanism, intrapopulation variation in distribution and growth may lead to considerable variation in fitness among families because these factors affect success in subsequent freshwater and marine life history stages.

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Application of Statistical Power Analysis to the Oregon Coho Salmon (Oncorhynchus kisutch) Problem

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f89-154 ◽

1989 ◽

Vol 46 (7) ◽

pp. 1183-1187 ◽

Cited By ~ 30

Author(s):

Randall M. Peterman

Keyword(s):

Null Hypothesis ◽

Power Analysis ◽

Statistical Power ◽

Coho Salmon ◽

Alternative Hypothesis ◽

Oncorhynchus Kisutch ◽

Current Data ◽

Density Dependent ◽

Consistent Increase ◽

Marine Survival

Nickelson (1986; Can. J. Fish. Aquat. Sci. 43: 527–535) was unable to reject the null hypothesis (Ho) of density-independent marine survival rate for Oregon coho salmon (Oncorhynchus kisutch) when wild, private hatchery, and public hatchery stocks were analyzed separately. Thus, even though there appears to have been no consistent increase in adult abundance in recent years in spite of large increases in smolt abundance, Nickelson's analysis does not support the alternative hypothesis (HA) of density-dependent marine survival. Some fishery managers are using Nickelson's results to support proposals to increase smolt production further. I calculated statistical power for these cases, i.e. the probability that the null hypothesis of density-independence could have been rejected, even if marine survival were truly density-dependent. Power was below 0.19 for all cases, which meant that Nickelson (1986) had at least an 81% chance of making a Type II error (incorrectly accepting Ho), if Ho was actually false. Therefore, Oregon fishery managers should be cautious about making decisions on increased smolt production based on current data; they run a high risk of mistakenly assuming density-independent marine survival. More generally, managers should not take action based on a failure to reject a null hypothesis unless power is high.

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