Relative importance of chinook salmon abundance on resident killer whale population growth and viability (original) (raw)
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PloS one, 2011
Ecosystem-based management (EBM) of marine resources attempts to conserve interacting species. In contrast to single-species fisheries management, EBM aims to identify and resolve conflicting objectives for different species. Such a conflict may be emerging in the northeastern Pacific for southern resident killer whales (Orcinus orca) and their primary prey, Chinook salmon (Oncorhynchus tshawytscha). Both species have at-risk conservation status and transboundary (Canada-US) ranges. We modeled individual killer whale prey requirements from feeding and growth records of captive killer whales and morphometric data from historic live-capture fishery and whaling records worldwide. The models, combined with caloric value of salmon, and demographic and diet data for wild killer whales, allow us to predict salmon quantities needed to maintain and recover this killer whale population, which numbered 87 individuals in 2009. Our analyses provide new information on cost of lactation and new pa...
Canadian Journal of Fisheries and Aquatic Sciences, 2018
Predation risk and competition among conspecifics significantly affect survival of juvenile salmon, but are rarely incorporated into models that predict recruitment in salmon populations. Using densities of harbour seals (Phoca vitulina) and numbers of hatchery-released Chinook salmon (Oncorhynchus tshawytscha) smolts as covariates in spatially structured Bayesian hierarchical stock–recruitment models, we found significant negative correlations between seal densities and productivity of Chinook salmon for 14 of 20 wild Chinook populations in the Pacific Northwest. Changes in numbers of seals since the 1970s were associated with a 74% decrease (95% CI: −85%, −64%) in maximum sustainable yield in Chinook stocks. In contrast, hatchery releases were significantly correlated with Chinook productivity in only one of 20 populations. Our findings are consistent with recent research on predator diets and bioenergetics modeling that suggest there is a relationship between harbour seal predati...
Conservation …, 2006
The viability of populations is influenced by driving forces such as density dependence and climate variability, but most population viability analyses (PVAs) ignore these factors because of data limitations. Additionally, simplified PVAs produce limited measures of population viability such as annual population growth rate ( λ) or extinction risk. Here we developed a "mechanistic" PVA of threatened Chinook salmon (Oncorhynchus tshawytscha) in which, based on 40 years of detailed data, we related freshwater recruitment of juveniles to density of spawners, and third-year survival in the ocean to monthly indices of broad-scale ocean and climate conditions. Including climate variability in the model produced important effects: estimated population viability was very sensitive to assumptions of future climate conditions and the autocorrelation contained in the climate signal increased mean population abundance while increasing probability of quasi extinction. Because of the presence of density dependence in the model, however, we could not distinguish among alternative climate scenarios through mean λ values, emphasizing the importance of considering multiple measures to elucidate population viability. Our sensitivity analyses demonstrated that the importance of particular parameters varied across models and depended on which viability measure was the response variable. The density-dependent parameter associated with freshwater recruitment was consistently the most important, regardless of viability measure, suggesting that increasing juvenile carrying capacity is important for recovery.
Demographic changes in Chinook salmon across the Northeast Pacific Ocean
Fish and Fisheries
Populations respond to a variety of natural and anthropogenic factors that alter their dynamics and demography. The age-structure and sizestructure of populations are responsive to environmental conditions, harvesting by humans, fluctuations in population density, diseases and species interactions such as predation, via changes in individual growth and size-dependent mortality. Intense harvesting can lead to agetruncated or juvenescent populations and thus reduced average sizes
Ecology, 2010
We empirically assess the relationship between population growth rate (k, a parameter central to ecology) and effective population size (N e , a key parameter in evolutionary biology). Recent theoretical and numerical studies indicate that in semelparous species with variable age at maturity (such as Pacific salmon, many monocarpic plants, and various other species), differences in mean reproductive success among individuals reproducing in different years leads to variation in k, and this in turn can reduce N e . However, this phenomenon has received little empirical evaluation. We examined time series of abundance data for 56 populations of chinook salmon (Onchorhynchus tshawytscha) from the northwestern United States and compared N e (calculated from demographic data) with the total number of spawners each generation (N T ). Important results include: (1) The mean multigenerational ratioÑ e /Ñ T was 0.64 (median ¼ 0.67), indicating that annual variation in k reduces effective population size in chinook salmon by an average of ;35%. These reductions are independent of, and in addition to, factors that reduce N e within individual cohorts (uneven sex ratio and greater-than-random variance in reproductive success). (2) The coefficient of variation of k was the most important factor associated with reductions in N e , explaining up to two-thirds of the variance inÑ e /Ñ T . (3) Within individual generations, N e was lower when there was a negative correlation between annual N i and k, i.e., when relatively few breeders produced relatively high numbers of offspring. Our results thus highlight an important and little-studied eco-evolutionary trade-off: density-dependent compensation has generally favorable ecological consequences (promoting stability and long-term viability) but incurs an evolutionary cost (reducing N e because a few individuals make a disproportionate genetic contribution). (4) For chinook salmon,N eH (an estimator based on the harmonic mean number of breeders per year) is generally a good proxy for true N e and requires much less data to calculate.
The salmon MALBEC Project: a North Pacific-scale study to support salmon conservation planning
2009
The Model for Assessing Links Between Ecosystems (MALBEC) is a policy gaming tool with potential to explore the impacts of climate change, harvest policies, hatchery policies, and freshwater habitat capacity changes on salmon at the North Pacific scale. This article provides background information on the MALBEC project, methods, input data, and preliminary results pertaining to (1) hatchery versus wild salmon production in the North Pacific Ocean, (2) rearing, movement, and interactions among Pacific salmon populations in marine environments, (3) marine carrying capacities, density-dependent growth, and survival in Pacific salmon stocks, and (4) climate impacts on productivity in salmon habitat domains across the North Pacific. The basic modeling strategy underlying MALBEC follows the full life cycle of salmon and allows for density-dependence at multiple life stages, and it includes spatially explicit ecosystem considerations for both freshwater and marine habitat. The model is supported by a data base including annual run sizes, catches, spawning escapements, and hatchery releases for 146 regional stock groups of hatchery and wild pink, chum, and sockeye salmon around the North Pacific for the period 1952-2006. For this historical period, various hypotheses about density-dependent interactions in the marine environment are evaluated based on the goodness-of-fit between simulated and observed annual run sizes. Based on the information we used to inform our ocean migration table, interactions among stocks that originate from geographically distant regions are greatest in the Bering Sea in summer-fall and in the eastern sub-Arctic in winter-spring. While the model does not reproduce the observed data for some specific stock groups, it does predict the same overall production pattern that was observed by reconstructing run sizes with catch and escapement data alone. Our preliminary results indicate that simulations that include density-dependent interactions in the ocean yield better fits to the observed run-size data than those simulations without density-dependent interactions in the ocean. This suggests that for any level of ocean productivity, the ocean will only support a certain biomass of fish but that this biomass could consist of different combinations of stocks, stock numbers and individual fish sizes. MALBEC simulations illustrate this point by showing that under scenarios of Pacific-wide reduced hatchery production, the total number of wild Alaskan chum salmon increases, and that such increases are large where density-dependent effects on survival are large and small where they are not. Under scenarios with reduced freshwater carrying capacities for wild stocks, the impacts of density-dependent interactions also lead to relative increases in ocean survival and growth rates for stocks using ocean habitats where density-dependence is large.
1996
Distribution of pa for Priest Rapids chinook. Total biomass of hatchery contributions to Columbia River, 1976-89. Map of hatcheries used in this analysis. Normalized residual plots for Hilborn model, not adjusted for transportation. 8 8 9 9 Normalized residual plots for Hilborn model, adjusted for transportation. Normalized residual plots for CWT observed adult counts, not adjusted for transportation. Normalized residual plots for CWT observed adults counts, adjusted for transportation. Normalized residual plots for VPA estimates of survival to age 2. not adjusted for transportation. Normalized residual plots for VPA estimates of survival to age 2, adjusted for transportation. Summary of R' for single river conditions for the Hilborn et al. (1993a.b) model (1). unadjusted for probability of transportation. Summary table for best fit models using Hilborn et al. (1993a.b) model (1). unadjusted for the probability of transportation. Standard errors of the coefficient estimation are in parenthesis. Summary of R2 for single river conditions for the Hilborn et al. (1993a.b) log-linear model (2). adjusted for probability of transportation. Summary table for best fit models using log-linear response model (2). adjusted for the probability of transportation. Standard errors of the coefficient estimation are in parenthesis. Summary of R2 for single river conditions for each reference hatchery stock, using log-linear response model (3). unadjusted for probability of transportation. Summary table for the best models for each reference stock using loglinear response model (3). unadjusted for the probability of transportation. Standard errors of the coefficient estimation are in parentheses.. Summary of RL for single river conditions for each reference hatchery stock, using log-linear response model (4), adjusted for the probability of transportation. Summary table for best models for each reference stock using log-linear response model (4). adjusted for the probability of transportation. Standard errors of the coefficient estimation are in parentheses. Summary R2 for single river conditions for each reference hatchery stock, using log-linear response model (5) using VPA estimates, unadjusted for probability of transportation. Asterisk indicates factors significant at P ~2 0.05. Summary table for the best models for each reference stock using loglinear response model (5) based on VPA estimates, unadjusted for the probability of transportation. Standard errors of the coefficient estimation are in parentheses. Summary of R2 for single river conditions for each reference hatchery stock, using log-linear response model (6) based on VPA estimates, adjusted for probability of transportation.
Canadian Journal of Fisheries and Aquatic Sciences, 2017
Conflicts can arise when the recovery of one protected species limits the recovery of another through competition or predation. The recovery of many marine mammal populations on the west coast of the United States has been viewed as a success; however, within Puget Sound in Washington State, the increased abundance of three protected pinniped species may be adversely affecting the recovery of threatened Chinook salmon (Oncorhynchus tshawytscha) and endangered killer whales (Orcinus orca) within the region. Between 1970 and 2015, we estimate that the annual biomass of Chinook salmon consumed by pinnipeds has increased from 68 to 625 metric tons. Converting juvenile Chinook salmon into adult equivalents, we found that by 2015, pinnipeds consumed double that of resident killer whales and six times greater than the combined commercial and recreational catches. We demonstrate the importance of interspecific interactions when evaluating species recovery. As more protected species respond ...
Salmon As Status Indicators for North Pacific Ecosystems
Bulletin No, 2007
A new system of salmon status categorization will provide useful indicators of ocean conditions and climate variability in the North Pacific Ocean. Under Canada's new Wild Salmon Policy, biological status will be assessed and categorized for a few hundred largely independent lineages of chinook, sockeye, coho, chum, and pink salmon. Changes to the status of these Conservation Units, information regarding their oceanic distribution, and biological characteristics of fish returning to fresh water to spawn will be linked to the status of marine ecosystems. Data from short-lived species like pink salmon will inform the management of longer-lived species, including fish other than salmon. Each Conservation Unit will be categorized into one of three status zones based on the abundance and distribution of spawners or proxies thereof. Intensive studies of salmon returning to selected streams will determine the relative importance of factors operating in fresh versus oceanic waters and the role of natural vs. anthropogenic factors (e.g. fishing) on Conservation Unit status. These types of information collectively should provide important clues to marine health and carrying capacity. Things should also work the other way-ecosystem data (including oceanographic) will aid in the management of salmon and other marine species.
Requirements and availability of prey for northeastern pacific southern resident killer whales
PLOS ONE
The salmon-eating Southern Resident killer whale (SRKW) (Orcinus orca) population currently comprises only 73 individuals, and is listed as ‘endangered’ under the Species at Risk Act in Canada. Recent evidence suggests that the growth of this population may be limited by food resources, especially Chinook salmon (Oncorhynchus tshawytscha). We present spatio-temporal bioenergetics model for SRKW in the Salish Sea and the West Coast of Vancouver Island from 1979–2020 with the objective of evaluating how changes in the abundance, age-structure, and length-at-age of Chinook salmon populations has influenced the daily food consumption of the SRKW population. Our model showed that the SRKW population has been in energetic deficit for six of the last 40 years. Our results also suggested that the abundance of age-4 and age-5 Chinook salmon are significant predictors of energy intake for SRKW. We estimated that the annual consumption (April-October) of Chinook salmon by the whales between 19...