Hagen C.A.,1374 Parrell Road |
Loughin T.M.,Simon Fraser University |
Budeau D.A.,406 Cherry Avenue NE |
Reishus B.S.,406 Cherry Avenue NE
Journal of Wildlife Management | Year: 2012
Ratio of immature (young of the year) grouse to adult birds (I:A) in the harvest of upland game birds is commonly used as an index to annual reproduction; however, I:A ratios can vary as the season progresses producing biased estimates. We analyzed I:A ratios in the daily harvest of dusky grouse (Dendragopus obscurus) and ruffed grouse (Bonasa umbellus) in northeastern Oregon over 28 years (1981-2008) and found that I:A ratios in the harvest declined for both species as the hunting season progressed. We also analyzed ratios of adult female to adult male (AF:AM) grouse to determine if female and male grouse were harvested in equal numbers throughout the harvest season. We found that more males than females of both species were harvested, but that AF:AM ratio of both dusky and ruffed grouse did not change during most of the hunting season. Approximately 50% of the annual harvest occurred during the first 14 days of the hunting season. Therefore, we recommend using the ratios of I:A birds in the first 14 days of the harvest season as the best index to annual reproduction of forest grouse in northeast Oregon. © 2011 The Wildlife Society.
Chilcote M.W.,National Oceanic and Atmospheric Administration |
Goodson K.W.,406 Cherry Avenue NE |
Falcy M.R.,406 Cherry Avenue NE
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2011
We found a negative relationship between the reproductive performance in natural, anadromous populations of steelhead trout (Oncorhynchus mykiss), coho salmon (O. kisutch), and Chinook salmon (O. tshawytscha), and the proportion of hatchery fish in the spawning population. We used intrinsic productivity as estimated from fitting a variety of recruitment models to abundance data for each population as our indicator of reproductive performance. The magnitude of this negative relationship is such that we predict the recruitment performance for a population composed entirely of hatchery fish would be 0.128 of that for a population composed entirely of wild fish. The effect of hatchery fish on reproductive performance was the same among all three species. Further, the impact of hatchery fish from "wild type" hatchery broodstocks was no less adverse than hatchery fish from traditional, domesticated broodstocks. We also found no support for the hypothesis that a population's reproductive performance was affected by the length of exposure to hatchery fish. In most cases, measures that minimize the interactions between wild and hatchery fish will be the best long-term conservation strategy for wild populations.
Olson Z.H.,Purdue University |
Whittaker D.G.,406 Cherry Avenue NE |
Rhodes Jr. O.E.,Purdue University
Journal of Wildlife Management | Year: 2013
Because genetic diversity provides the substance for adaptation and evolution and its decline signifies the potential for deleterious effects on demography, biologists must understand how management action can facilitate or hinder the retention of genetic diversity at the level of the population being managed. We assessed genetic diversity in 8 reintroduced populations of bighorn sheep using 16 microsatellite markers and a 515-base-pair segment of the mitochondrial control region. Populations were categorized by their translocation histories: first-order populations were those established directly from large source populations, second-order populations were established using individuals from first-order populations, and populations with mixed translocation histories were those established or supplemented with sheep from more than 1 sample on a source population. Nuclear and mitochondrial datasets yielded complementary signals of declining genetic diversity (mixed > first order > second order) that differed predictably in magnitude. Our suite of microsatellites revealed that populations with mixed translocation histories had greater allelic richness (AR) and expected heterozygosity (H E) than second-order populations, but we found no statistical differences between mixed:first order or first:second order population pairs. Mitochondrial diversity, however, was limited to populations with mixed translocation histories. Similarly, we detected significant differentiation (FST) among most populations using data from microsatellites, but found major differentiation in mitochondrial diversity. All first-order and second-order populations shared a single haplotype, whereas mixed populations contained 6 haplotypes. Finally, estimates of effective population size (N e) derived from our microsatellite data were uniformly low (range 9-27), indicating that the maintenance of genetic diversity in the reintroduced populations of bighorn sheep in our study likely will require management action; possibly including future translocations and improvements in natural connectivity among populations. © The Wildlife Society, 2013.
Olson Z.H.,Purdue University |
Whittaker D.G.,406 Cherry Avenue NE |
Rhodes O.E.,Purdue University
Ecology and Evolution | Year: 2012
Positive demographic responses have been reported in several species where the immigration or supplementation of genetically distinct individuals into wild populations has resulted in a genetic rescue effect.However, rarely have researchers incorporatedwhat could be considerable risk of outbreeding depression into planning for genetic management programs.We assess the genetic effects of an experiment in genetic management involving replicate populations ofCalifornia bighorn sheep (Ovis canadensis californiana) in Oregon, USA, which previously experienced poor productivity and numerical declines. In the experiment, two declining populationswere supplemented with ewes from a more genetically diverse population of California bighorn sheep in Nevada.We incorporated analysis of genetic samples representing both experimental populations prior to supplementation, samples from the supplemented individuals, and samples collected from both experimental populations approximately one generation after supplementation. We used genetic analyses to assess the integration of supplemented and resident populations by identifying interpopulation hybrids. Further, we incorporated demographic simulations to assess the risk of outbreeding depression as a result of the experimental augmentation. Finally, we used data from microsatellites and mitochondrial sequences to determine if genetic management increased genetic diversity in the experimental populations. Our analyses demonstrated the success of genetic management by documenting interpopulation hybrids, identifying no evidence for outbreeding depression as a result of contact between the genetically distinct supplemented and resident populations, and by identifying increased population-level metrics of genetic diversity in postsupplementation populations compared with presupplementation levels. © 2012 The Authors.