The power of experiments for estimating relative reproductive success of hatchery-born spawners

Hinrichsen, Richard A.

doi:10.1139/f03-070

Cited by 8 publications

(9 citation statements)

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“…Census data relating to natural and hatchery spawners are available for a considerable number of Pacific salmon and steelhead populations (e.g., McClure et al 2003). Use of such data to determine hatchery-spawner effect on natural productivity can be aided by comparing population productivity in the presence or absence of hatchery supplementation (Hinrichsen 2003;Araki et al 2008).…”

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confidence: 99%

Natural Productivity in Steelhead Populations of Natural and Hatchery Origin: Assessing Hatchery Spawner Influence

Lister¹

2013

Trans Am Fish Soc

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Natural productivity, the number of natural-origin adult recruits per parent, is an important parameter for assessing population status of steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) and Pacific salmon Oncorhynchus spp. listed under the U.S. Endangered Species Act. Hatchery-origin adults comprise a majority of many salmon and steelhead spawning populations. In such cases, the utility of natural productivity estimates is affected by uncertain reproductive fitness of hatchery spawners and by possible ecological or genetic interactions among hatchery and natural fish. This study examined options for analyzing population census data to assess hatchery spawner effects on natural productivity of mixed steelhead populations including spawners of hatchery and natural origin. It compared productivity in three mixed and reference (natural) population pairs, and estimated productivity as natural recruits per total spawners of natural and hatchery origin (R nat /S tot ) or as natural recruits per natural spawner (R nat /S nat ). Natural productivity estimated as R nat /S tot reflected hatchery program scale, not productive capacity of natal streams. This analytical approach masked natural production dynamics in populations with a major hatchery spawner proportion, and was therefore of limited use for determining hatchery spawner influence. Productivity estimated as R nat /S nat indicated similar productivity of reference and mixed populations, and an absence of hatchery spawner effect, in the case of (1) a large hatchery stray component, and (2) a hatchery supplementation program. In the third pairing, R nat /S nat productivity of the mixed population significantly exceeded that of the reference population, suggesting natural spawner abundance is below carrying capacity. Hatchery spawners contributed to natural productivity in that case, but in the presence of reduced natural spawner density. These findings suggest that hatchery spawners are unlikely to affect natural production of a mixed steelhead population unless natural spawner abundance is below carrying capacity.

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confidence: 99%

Natural Productivity in Steelhead Populations of Natural and Hatchery Origin: Assessing Hatchery Spawner Influence

Lister¹

2013

Trans Am Fish Soc

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“…Unfortunately, current statistical approaches in parentage analyses have not addressed this crucial question. Previous work has addressed sample sizes required to differentiate reproductive success between 2 groups but not among individuals (Hinrichsen 2003). Others have addressed the minimum samples taken from a single nest or clutch to describe the genetic mating system (DeWoody et al 2000;Neff et al 2000), but these approaches do not require exhaustive sampling of parental genotypes and therefore fail to consider the parents that produce no offspring.…”

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confidence: 99%

A Model for Estimating the Minimum Number of Offspring to Sample in Studies of Reproductive Success

Ward

Carlson

2011

Journal of Heredity

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Molecular parentage permits studies of selection and evolution in fecund species with cryptic mating systems, such as fish, amphibians, and insects. However, there exists no method for estimating the number of offspring that must be assigned parentage to achieve robust estimates of reproductive success when only a fraction of offspring can be sampled. We constructed a 2-stage model that first estimated the mean (μ) and variance (v) in reproductive success from published studies on salmonid fishes and then sampled offspring from reproductive success distributions simulated from the μ and v estimates. Results provided strong support for modeling salmonid reproductive success via the negative binomial distribution and suggested that few offspring samples are needed to reject the null hypothesis of uniform offspring production. However, the sampled reproductive success distributions deviated significantly (χ(2) goodness-of-fit test p value < 0.05) from the known simulated reproductive success distribution at rates often >0.05 and as high as 0.24, even when hundreds of offspring were assigned parentage. In general, reproductive success patterns were less accurate when offspring were sampled from cohorts with larger numbers of parents and greater variance in reproductive success. Our model can be reparameterized with data from other species and will aid researchers in planning reproductive success studies by providing explicit sampling targets required to accurately assess reproductive success.

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“…This equation is equivalent to eq. 1 of Hinrichsen (2003). Our paper will concentrate on studies with data from one experiment because this study design has the lowest power and highest bias (Hinrichsen 2003).…”

Section: Estimating Relative Fitnessmentioning

confidence: 99%

“…However, the sampling distribution of estimates of relative fitness is not normal and is even asymmetric, so confidence limits estimated this way are unlikely to perform well. Hinrichsen (2003), for example, derived an expression for the approximate sampling variance for estimates of relative fitness, but did not use this variance in his power analysis. Authors reporting the relative fitness of different stocks of fish have usually not included measures of uncertainty in their work (for examples see Hinrichsen 2003).…”

Section: Introductionmentioning

confidence: 99%

Likelihood-based confidence intervals of relative fitness for a common experimental design

Kalinowski¹,

Taper²

2005

Can. J. Fish. Aquat. Sci.

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Statistical inferences concerning the relative fitness of different types of individuals in a population have not been well developed. We present a method for calculating confidence intervals for maximum likelihood estimates of relative fitness obtained from an experimental design that is common in the fisheries literature. Analysis and simulation show that these confidence limits are reliable. We also show that the bias of the estimates is low for realistic sample sizes.

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The power of experiments for estimating relative reproductive success of hatchery-born spawners

Cited by 8 publications

References 20 publications

Natural Productivity in Steelhead Populations of Natural and Hatchery Origin: Assessing Hatchery Spawner Influence

Natural Productivity in Steelhead Populations of Natural and Hatchery Origin: Assessing Hatchery Spawner Influence

A Model for Estimating the Minimum Number of Offspring to Sample in Studies of Reproductive Success

Likelihood-based confidence intervals of relative fitness for a common experimental design

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