The effects of spawning age distribution on salmon persistence in fluctuating environments

Hill, M. Forrest; Botsford, Louis W.; Hastings, Alan

doi:10.1046/j.1365-2656.2003.00745.x

Cited by 9 publications

(12 citation statements)

References 36 publications

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“…This result is mathematically similar to that of Gurney and Middleton (1996), who demonstrated that iteroparous organisms adopting an earlier onset of maturation become more advantageous under a stochastic environment. The present result is, furthermore, consistent with that of Hill et al (2003), which demonstrated that, under a stochastic environment, individuals with an indeterminate semelparous life-history strategy become more persistent than those with a determinate semelparous life-history strategy.…”

Section: Discussionsupporting

confidence: 91%

Effects of an autocorrelated stochastic environment and fisheries on the age at maturity of Chinook salmon

Fujiwara

2007

Theor Ecol

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Chinook salmon (Oncorhynchus tshawytscha) reproduce only once in their lifetime, and their age at reproduction varies among individuals (indeterminate semelparous). However, the factors that determine their spawning age still remain uncertain. Evidence from recent studies suggests that individual growth and reproduction of Chinook salmon are affected by the rate of coastal upwelling, which is shown to be positively autocorrelated between years. Therefore, the serially autocorrelated environmental is expected to play an important role in determining their spawning age. In the present study, I demonstrate the advantage of an indeterminate maturation strategy under a stochastic environment. I then present theoretical evidence for the advantage of adjusting the maturation probability based on the environment they experienced and demonstrate that fisheries reduce the fitness of the strategy to delay maturation. The results presented herein emphasize the importance of incorporating detailed life-history strategies of organisms when undertaking population management.

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Section: Discussionsupporting

confidence: 91%

Effects of an autocorrelated stochastic environment and fisheries on the age at maturity of Chinook salmon

Fujiwara

2007

Theor Ecol

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“…, 2001; MacCracken, 2004; Karraker et al. , 2006; Tait & Diller, 2006) and survival (Sagar, Olson & Schmitz, 2007 estimated D. tenebrosus annual survival), paired with the fact that anadromous fishes have complex and varied life histories that involve both freshwater and marine environments (Weitkamp & Neely, 2002; Hill, Botsford & Hastings, 2003; Shea, Wolf & Mangel, 2006), suggests that any statement about “similar life requisites” for salmon and SAA is at best premature, and at worst inaccurate.…”

Section: Four Unsubstantiated Assumptionsmentioning

confidence: 99%

Concerns regarding the use of amphibians as metrics of critical biological thresholds: a comment on Welsh & Hodgson (2008)

Kroll¹,

Hayes²,

MacCracken³

2009

Freshwater Biology

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Welsh & Hodgson (2008) argued that stream-associated amphibians (Ascaphus truei, Dicamptodon tenebrosus and Rhyacotriton variegatus) are reliable indicators of ecosystem health in the Pacific Northwest (PNW), U.S.A. We demonstrate that their assertions rely on circular reasoning as well as logical and empirical assumptions that have not received rigorous evaluation. 2. Welsh & Hodgson (2008) based their arguments on data collected in northwestern California, U.S.A. However, all three taxa occur across a wide range of environmental gradients in the PNW, and other research results suggest that the taxa respond differentially to environmental perturbations across their geographical distribution. Hence, differences in abundance are not always reliable indicators of the state of an ecosystem, as population numbers can be influenced by factors that may not be associated with habitat quality (e.g. predation and disease). (2008) present indices (rather than estimates) of abundance, which contain an unquantifiable amount of uncertainty not reliably attributable to either environmental or management factors. Evaluating parameters such as reproductive success and survival are more likely to provide strong inference about factors influencing population size than correlative studies that associate some measure of relative abundance with individual habitat features. 4. We argue that direct measurement of physical features (water temperature, sediment and wood), for which Welsh & Hodgson (2008) suggest using amphibians as surrogates, is more accurate, efficient and cost effective compared with monitoring cryptic species with methods that are unable to quantify spatial and temporal uncertainty in biological responses. 5. Headwater streams are critical components of catchments in the PNW, and all three amphibian taxa show strong associations with low-order streams. However, we think research and monitoring of headwater streams should be guided by hypotheses that evaluate causal mechanisms, rather than relying on descriptive patterns that are limited in geographical scope and which support only weak inference about ecosystem processes. Other studies provide direct links between physical features and responses of target populations (i.e. fish). Adding a second correlative link (i.e. amphibians) provides no Correspondence: A. J. Kroll, Welsh & Hodgson

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“…Furthermore, within a population, diverse life histories can contribute to stability . Using population models, Hill, Botsford & Hastings (2003) suggested that higher levels of diversity of Pacific salmon ocean ages can increase predicted persistence in the face of variable ocean survival. However, there remains an incomplete understanding of how diverse life-history traits within populations contribute to temporal stability of Pacific salmonids.…”

Section: Introductionmentioning

confidence: 99%

Life‐history diversity and its importance to population stability and persistence of a migratory fish: steelhead in two large North American watersheds

Moore

Yeakel

Peard

et al. 2014

Journal of Animal Ecology

165

162

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Summary1. Life-history strategies can buffer individuals and populations from environmental variability. For instance, it is possible that asynchronous dynamics among different life histories can stabilize populations through portfolio effects. 2. Here, we examine life-history diversity and its importance to stability for an iconic migratory fish species. In particular, we examined steelhead (Oncorhynchus mykiss), an anadromous and iteroparous salmonid, in two large, relatively pristine, watersheds, the Skeena and Nass, in north-western British Columbia, Canada. We synthesized life-history information derived from scales collected from adult steelhead (N = 7227) in these watersheds across a decade. 3. These migratory fishes expressed 36 different manifestations of the anadromous life-history strategy, with 16 different combinations of freshwater and marine ages, 7Á6% of fish performing multiple spawning migrations, and up to a maximum of four spawning migrations per lifetime. Furthermore, in the Nass watershed, various life histories were differently prevalent through time -three different life histories were the most prevalent in a given year, and no life history ever represented more than 45% of the population. 4. These asynchronous dynamics among life histories decreased the variability of numerical abundance and biomass of the aggregated population so that it was > 20% more stable than the stability of the weighted average of specific life histories: evidence of a substantial portfolio effect. Year of ocean entry was a key driver of dynamics; the median correlation coefficient of abundance of life histories that entered the ocean the same year was 2Á5 times higher than the median pairwise coefficient of life histories that entered the ocean at different times. Simulations illustrated how different elements of life-history diversity contribute to stability and persistence of populations. 5. This study provides evidence that life-history diversity can dampen fluctuations in population abundances and biomass via portfolio effects. Conserving genetic integrity and habitat diversity in these and other large watersheds can enable a diversity of life histories that increases population and biomass stability in the face of environmental variability.

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The effects of spawning age distribution on salmon persistence in fluctuating environments

Cited by 9 publications

References 36 publications

Effects of an autocorrelated stochastic environment and fisheries on the age at maturity of Chinook salmon

Effects of an autocorrelated stochastic environment and fisheries on the age at maturity of Chinook salmon

Concerns regarding the use of amphibians as metrics of critical biological thresholds: a comment on Welsh & Hodgson (2008)

Life‐history diversity and its importance to population stability and persistence of a migratory fish: steelhead in two large North American watersheds

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