Genetic Monitoring of Threatened Chinook Salmon Populations: Estimating Introgression of Nonnative Hatchery Stocks and Temporal Genetic Changes

Doornik, Donald M. Van; Eddy, Debra L.; Waples, Robin S.; Boe, Stephen J.; Hoffnagle, Timothy L.; Berntson, Ewann A.; Moran, Paul

doi:10.1080/02755947.2013.790861

Cited by 16 publications

(15 citation statements)

References 49 publications

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“…Previous analyses have suggested that hatchery fish have had minimal influence on genetic diversity in this ESU despite high numbers of hatchery strays on spawning grounds (Van Doornik et al. , , Matala et al. ).…”

Section: Discussionmentioning

confidence: 88%

Setting spatial conservation priorities despite incomplete data for characterizing metapopulations

Fullerton

Anzalone

Moran

et al. 2016

Ecological Applications

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Management of spatially structured species poses unique challenges. Despite a strong theoretical foundation, practitioners rarely have sufficient empirical data to evaluate how populations interact. Rather, assumptions about connectivity and source-sink dynamics are often based on incomplete, extrapolated, or modeled data, if such interactions are even considered at all. Therefore, it has been difficult to evaluate whether spatially structured species are meeting conservation goals. We evaluated how estimated metapopulation structure responded to estimates of population sizes and dispersal probabilities and to the set of populations included. We then compared outcomes of alternative management strategies that target conservation of metapopulation processes. We illustrated these concepts for Chinook salmon (Oncorhynchus tshawytscha) in the Snake River, USA. Our description of spatial structure for this metapopulation was consistent with previous characterizations. We found substantial differences in estimated metapopulation structure when we had incomplete information about all populations and when we used different sources of data (three empirical, two modeled) to estimate dispersal, whereas responses to population size estimates were more consistent. Together, these findings suggest that monitoring efforts should target all populations occasionally and populations that play key roles frequently and that multiple types of data should be collected when feasible. When empirical data are incomplete or of uneven quality, analyses using estimates produced from an ensemble of available datasets can help conservation planners and managers weigh near-term options. Doing so, we found trade-offs in connectivity and source dominance in metapopulation-level responses to alternative management strategies that suggest which types of approaches may be inherently less risky.

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Section: Discussionmentioning

confidence: 88%

Setting spatial conservation priorities despite incomplete data for characterizing metapopulations

Fullerton

Anzalone

Moran

et al. 2016

Ecological Applications

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“…Empirical studies of the spatiotemporal relationship between N and N b among populations spanning a large gradient of population sizes are rare (Van Doornik et al . ; Perrier et al . ).…”

Section: Discussionmentioning

confidence: 99%

Spatiotemporal relationship between adult census size and genetic population size across a wide population size gradient

Bernos

Fraser

2016

Molecular Ecology

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Adult census population size (N) and effective number of breeders (Nb ) are highly relevant for designing effective conservation strategies. Both parameters are often challenging to quantify, however, making it of interest to determine whether one parameter can be generalized from the other. Yet, the spatiotemporal relationship between N and Nb has not been well characterized empirically in many taxa. We analysed this relationship for 5-7 consecutive years in twelve brook trout populations varying greatly in N (49-10032) and Nb (3-567) and identified major environmental variables affecting the two parameters. N or habitat size alone explained 47-57% of the variance in Nb , and Nb was strongly correlated with effective population size. The ratio Nb /N ranged from 0.01 to 0.45 and increased at small N or following an annual decrease in N, suggesting density-dependent constraints on Nb . We found no evidence for a consistent, directional difference between variability in Nb and/or Nb /N among small and large populations; however, small populations had more varying temporal variability in Nb /N ratios than large populations. Finally, Nb and Nb /N were 2.5- and 2.3-fold more variable among populations than temporally within populations. Our results demonstrate a clear linkage between demographic and evolutionary parameters, suggesting that Nb could be used to approximate N (or vice versa) in natural populations. Nevertheless, using one variable to infer the other to monitor trends within populations is less recommended, perhaps even less so in small populations given their less predictable Nb vs. N dynamics.

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“…Total hatchery releases of Chinook salmon into the Pacific Ocean increased substantially during the 1970s and somewhat during the 1980s and have since been declining (Figure ). Hatchery‐reared fish could alter the age‐size structures of populations coast‐wide via two mechanisms: direct effects on competition for resources in the ocean (Ruggerone & Goetz, ), or as a consequence of selective breeding and introgression of selected genotypes into wild populations, especially small populations in close geographic proximity to hatcheries (Van Doornik et al., ). The selective breeding of Chinook salmon in hatcheries might have produced faster‐growing fish that attain larger sizes during the first two or 3 years in the ocean but do not reach larger maximum sizes compared to wild fish.…”

Section: Discussionmentioning

confidence: 99%

Demographic changes in Chinook salmon across the Northeast Pacific Ocean

et al. 2018

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The demographic structure of populations is affected by life history strategies and how these interact with natural and anthropogenic factors such as exploitation, climate change, and biotic interactions. Previous work suggests that the mean size and age of some North American populations of Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) are declining. These trends are of concern because Chinook salmon are highly valued commercially for their exceptional size and because the loss of the largest and oldest individuals may lead to reduced population productivity. Using long‐term data from wild and hatchery populations, we quantified changes in the demographic structure of Chinook salmon populations over the past four decades across the Northeast Pacific Ocean, from California through western Alaska. Our results show that wild and hatchery fish are becoming smaller and younger throughout most of the Pacific coast. Proportions of older age classes have decreased over time in most regions. Simultaneously, the length‐at‐age of older fish has declined while the length‐at‐age of younger fish has typically increased. However, negative size trends of older ages were weak or non‐existent at the southern end of the range. While it remains to be explored whether these trends are caused by changes in climate, fishing practices or species interactions such as predation, our qualitative review of the potential causes of demographic change suggests that selective removal of large fish has likely contributed to the apparent widespread declines in average body sizes.

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Genetic Monitoring of Threatened Chinook Salmon Populations: Estimating Introgression of Nonnative Hatchery Stocks and Temporal Genetic Changes

Cited by 16 publications

References 49 publications

Setting spatial conservation priorities despite incomplete data for characterizing metapopulations

Setting spatial conservation priorities despite incomplete data for characterizing metapopulations

Spatiotemporal relationship between adult census size and genetic population size across a wide population size gradient

Demographic changes in Chinook salmon across the Northeast Pacific Ocean

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