Differential response of marine populations to climate forcing

2003 ◽  
Vol 60 (8) ◽  
pp. 971-985 ◽  
Author(s):  
Kevin S McCann ◽  
Louis W Botsford ◽  
Alan Hasting
Keyword(s):  
Density Dependence ◽  
Age Structure ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Environmental Variability ◽  
Climate Forcing ◽  
Dungeness Crab ◽  
Cancer Magister ◽  
Environmental Forcing ◽  
Variable Recruitment

In searching for causes of fluctuations in marine populations, investigators often assume that populations respond on the same time scale as the environmental forcing period, but this may not hold true. Here we show how the response of populations to variable recruitment changes with the degree of overcompensation using models of two species with similar age structure but different density-dependent recruitment, chinook salmon (Oncorhynchus tshawytscha) and Dungeness crab (Cancer magister). For compensatory density dependence, as in chinook salmon, variability in recruitment tends to follow the period in environmental variability over all time scales. For overcompensatory density dependence, as in Dungeness crab, variability in recruitment follows the environmental variability only for periods much greater than the maximum age of the population. For periods in environmental variability less than the maximum age, the dominant period of the population response is slightly larger than the length of the age structure. Here, strong overcompensatory recruitment acts to filter out potentially good recruitment years, resulting in dominant periodicities slightly larger than the length of the age structure. These mechanisms appear to explain the differences between observed spectra of Dungeness crab and chinook salmon.

scholarly journals Weakening portfolio effect strength in a hatchery-supplemented Chinook salmon population complex

2015 ◽  
Vol 72 (12) ◽  
pp. 1860-1875 ◽  
Author(s):  
William H. Satterthwaite ◽  
Stephanie M. Carlson
Keyword(s):  
Chinook Salmon ◽  
North Pacific ◽  
Oncorhynchus Tshawytscha ◽  
Environmental Variability ◽  
Central Valley ◽  
Simultaneous Increase ◽  
Environmental Forcing ◽  
Salmon Population ◽  
Portfolio Effect ◽  
Considerable Degradation

Biocomplexity contributes to asynchronous population dynamics, buffering stock complexes in temporally variable environments, a phenomenon referred to as a “portfolio effect”. We previously revealed a weakened but persistent portfolio effect in California’s Central Valley fall-run Chinook salmon (Oncorhynchus tshawytscha), despite considerable degradation and loss of habitat. Here, we further explore the timing of changes in variability and synchrony and relate these changes to factors hypothesized to influence variability in adult abundance, including hatchery release practices and environmental variables. We found evidence for increasing synchrony among fall-run populations that coincided temporally with increased off-site hatchery releases into the estuary but not with increased North Pacific environmental variability (measured by North Pacific Gyre Oscillation), nor were common trends well explained by a suite of environmental covariates. Moreover, we did not observe a simultaneous increase in synchrony in the nearby Klamath–Trinity system, where nearly all hatchery releases are on-site. Wavelet analysis revealed that variability in production was higher and at a longer time period later in the time series, consistent with increased environmental forcing and a shift away from dynamics driven by natural spawners.

scholarly journals Ecological thresholds in forecast performance for key United States West Coast Chinook salmon stocks

2019 ◽  
Vol 77 (4) ◽  
pp. 1503-1515 ◽  
Author(s):  
William H Satterthwaite ◽  
Kelly S Andrews ◽  
Brian J Burke ◽  
Jennifer L Gosselin ◽  
Correigh M Greene ◽  
...  
Keyword(s):  
Chinook Salmon ◽  
West Coast ◽  
Oncorhynchus Tshawytscha ◽  
Environmental Variability ◽  
Puget Sound ◽  
Threshold Dynamics ◽  
Time Lags ◽  
Environmental Indices ◽  
Forecast Performance ◽  
Salmon Fisheries

Abstract Preseason abundance forecasts drive management of US West Coast salmon fisheries, yet little is known about how environmental variability influences forecast performance. We compared forecasts of Chinook salmon (Oncorhynchus tshawytscha) against returns for (i) key California-Oregon ocean fishery stocks and (ii) high priority prey stocks for endangered Southern Resident Killer Whales (Orcinus orca) in Puget Sound, Washington. We explored how well environmental indices (at multiple locations and time lags) explained performance of forecasts based on different methods (i.e. sibling-based, production-based, environment-based, or recent averages), testing for nonlinear threshold dynamics. For the California stocks, no index tested explained >50% of the variation in forecast performance, but spring Pacific Decadal Oscillation and winter North Pacific Index during the year of return explained >40% of the variation for the sibling-based Sacramento Fall Chinook forecast, with nonlinearity and apparent thresholds. This suggests that oceanic conditions experienced by adults (after younger siblings returned) have the most impact on sibling-based forecasts. For Puget Sound stocks, we detected nonlinear/threshold relationships explaining >50% of the variation with multiple indices and lags. Environmental influences on preseason forecasts may create biases that render salmon fisheries management more or less conservative, and therefore could motivate the development of ecosystem-based risk assessments.

Effects of Environmental Forcing on Age-Structured Populations: Northern California Dungeness Crab (Cancer magister) as an Example

1986 ◽  
Vol 43 (11) ◽  
pp. 2345-2352 ◽  
Author(s):  
Louis W. Botsford
Keyword(s):  
Time Series ◽  
Size Distribution ◽  
Dungeness Crab ◽  
Cohort Size ◽  
Cancer Magister ◽  
Environmental Forcing ◽  
Harvest Rate ◽  
Density Dependent ◽  
Constant Rate ◽  
Recruitment Time

Evaluation of potential environmental effects on recruitment requires knowing how environmental forcing can affect recruitment and subsequent catch, and how these effects depend on life history. General relationships between a time series of an environmental forcing variable, the resulting time series of recruitment, and the subsequent time series of catch or abundance are described here for a fishery in which environmental forcing affects density-dependent recruitment and the population is fished at a constant rate. For a stable population with overcompensatory, density-dependent recruitment, the recruitment time series will resemble the environmental time series except that frequencies near 1/(2 × mean age in the population) will be emphasized. The amount of selective emphasis will depend on the degree of overcompensation, harvest rate, and width of the cohort size distribution (in a size-selective fishery). For a population harvested at constant rate, the catch time series will resemble the recruitment time series except that lower frequencies will be emphasized. The degree of selective emphasis will depend on harvest rate and width of the cohort size distribution. Application of these results to Dungeness crab (Cancer magister) research has allowed analysis of combined effects of density dependence and environmental forcing. They show (1) that criteria formerly used to evaluate density-dependent recruitment mechanisms were too strict, (2) that female harvest could reduce harvest variability due to environmental forcing, and (3) how a nonlinear influence of spring wind stress in combination with density-dependent recruitment could cause the observed catch record. Implications for other crustacean populations are discussed.

Consequences of potential density-dependent mechanisms on recovery of ocean-type chinook salmon (Oncorhynchus tshawytscha)

2004 ◽  
Vol 61 (4) ◽  
pp. 590-602 ◽  
Author(s):  
Correigh M Greene ◽  
Timothy J Beechie
Keyword(s):  
Density Dependence ◽  
Chinook Salmon ◽  
Habitat Restoration ◽  
Oncorhynchus Tshawytscha ◽  
High Sensitivity ◽  
Leslie Matrix ◽  
Relative Importance ◽  
Density Dependent ◽  
Habitat Area ◽  
Leslie Matrix Model

Restoring salmon populations depends on our ability to predict the consequences of improving aquatic habitats used by salmon. Using a Leslie matrix model for chinook salmon (Oncorhynchus tshawytscha) that specifies transitions among spawning nests (redds), streams, tidal deltas, nearshore habitats, and the ocean, we compared the relative importance of different habitats under three density-dependent scenarios: juvenile density independence, density-dependent mortality within streams, delta, and nearshore, and density-dependent migration among streams, delta, and nearshore. Each scenario assumed density dependence during spawning. We examined how these scenarios influenced priorities for habitat restoration using a set of hypothetical watersheds whose habitat areas could be systematically varied, as well as the Duwamish and Skagit rivers. In all watersheds, the three scenarios shared high sensitivity to changes in in nearshore and ocean mortality and produced similar responses to changes in other parameters controlling mortality (i.e., habitat quality). However, the three scenarios exhibited striking variation in population response to changes in habitat area (i.e., capacity). These findings indicate that nearshore habitat relationships may play significant roles for salmon populations and that the relative importance of restoring habitat area will depend on the mechanism of density dependence influencing salmon stocks.

Wind Stress and Cycles in Dungeness Crab (Cancer magister) Catch off California, Oregon, and Washington

1986 ◽  
Vol 43 (4) ◽  
pp. 838-845 ◽  
Author(s):  
David F. Johnson ◽  
Louis W. Botsford ◽  
Richard D. Methot Jr. ◽  
Thomas C. Wainwright
Keyword(s):  
Wind Stress ◽  
Time Lag ◽  
Northern California ◽  
Dungeness Crab ◽  
Cancer Magister ◽  
Cyclic Pattern ◽  
Environmental Forcing ◽  
Larval Phase ◽  
Crab Larvae ◽  
Time Required

Dungeness crab (Cancer magister) catch records along the coasts of northern California, Oregon, and Washington covary in a cyclic pattern with a period of 9–10 yr. Both environmental forcing and density-dependent recruitment have been proposed as the mechanisms causing these cycles. Spring wind stress in a southward direction is correlated with crab catch along this coast at typical lags of 4 and 5 yr. This time lag corresponds to the time required for growth from the larval phase to the size caught in the fishery. Also, computed autocorrelations show that wind stress is itself cyclic. Since crab larvae appear to be transported offshore and northward during the early larval phase, the observed correlation may result from a dependence of subsequent successful settlement on wind-driven southward, onshore transport during the late larval phae in the spring. However, the exact mechanisms are not known. The computed correlations indicate that wind stress may contribute to the observed cycles.

Effect of Individual Growth Rates on Expected Behavior of the Northern California Dungeness Crab (Cancer magister) Fishery

1984 ◽  
Vol 41 (1) ◽  
pp. 99-107 ◽  
Author(s):  
Louis W. Botsford
Keyword(s):  
Age Structure ◽  
Growth Pattern ◽  
Specific Model ◽  
Individual Growth ◽  
Time Lags ◽  
Northern California ◽  
Dungeness Crab ◽  
Cancer Magister ◽  
Density Dependent ◽  
The Mean

Cycles in the northern California Dungeness crab (Cancer magister) fishery may be caused by density-dependent recruitment or a cyclic environmental variable. Investigation of these potential causes requires knowledge of the age(s) at which crabs enter the fishery. Behavior of this fishery has previously been analyzed using mathematical models that include density-dependent recruitment and describe changes in age structure with time. From data available on the northern California crab population and a review of previous studies elsewhere it appears that a single year-class of crabs enters this fishery over several years rather than in one year as described by models with only age structure. The realism of models of this fishery can therefore be increased by including size structure. Behavior of size-specific models is in general different from that of age-specific models. However, it is shown here that an effective survival rate can be derived from a size-specific model that enables interpretation as an age-specific model. This is used to demonstrate that inclusion of size dispersion in a population model increases stability, but if the mean age of the population is not changed, it will not substantially change the period of cycles. Because the growth pattern developed here changes the mean age of entry into the fishery it results in cycles with a longer period than determined in previous analyses. With regard to environmental causes, this growth pattern implies time lags of 4 and 5 yr between an environmental factor affecting recruitment and its effect on the catch record.

scholarly journals Can late stage marine mortality explain observed shifts in age structure of Chinook salmon?

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247370
Author(s):  
Kaitlyn A. Manishin ◽  
Curry J. Cunningham ◽  
Peter A. H. Westley ◽  
Andrew C. Seitz
Keyword(s):  
Age Structure ◽  
Chinook Salmon ◽  
Late Stage ◽  
Marine Mammals ◽  
Potential Role ◽  
Oncorhynchus Tshawytscha ◽  
Pacific Salmon ◽  
Yukon River ◽  
Abrupt Shifts

Chinook salmon (Oncorhynchus tshawytscha) populations have experienced widespread declines in abundance and abrupt shifts toward younger and smaller adults returning to spawn in rivers. The causal agents underpinning these shifts are largely unknown. Here we investigate the potential role of late-stage marine mortality, defined as occurring after the first winter at sea, in driving this species’ changing age structure. Simulations using a stage-based life cycle model that included additional mortality during after the first winter at sea better reflected observed changes in the age structure of a well-studied and representative population of Chinook salmon from the Yukon River drainage, compared with a model estimating environmentally-driven variation in age-specific survival alone. Although the specific agents of late-stage mortality are not known, our finding is consistent with work reporting predation by salmon sharks (Lamna ditropis) and marine mammals including killer whales (Orcinus orca). Taken as a whole, this work suggests that Pacific salmon mortality after the first winter at sea is likely to be higher than previously thought and highlights the need to investigate selective sources of mortality, such as predation, as major contributors to rapidly changing age structure of spawning adult Chinook salmon.

Systematic hexamitid (Protozoa: Diplomonadida) Infection in seawater pen-reared Chinook salmon Oncorhynchus tshawytscha

1992 ◽  
Vol 14 ◽  
pp. 81-89 ◽  
Author(s):  
ML Kent ◽  
J Ellis ◽  
JW Fournie ◽  
SC Dawe ◽  
JW Bagshaw ◽  
...  
Keyword(s):  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha

Effect of salted-drying on bioactive compounds and microbiological changes during the processing of karasumi-like Chinook salmon (Oncorhynchus tshawytscha) roe product

2021 ◽  
Vol 357 ◽  
pp. 129780
Author(s):  
Senni Bunga ◽  
Mirja Kaizer Ahmmed ◽  
Alan Carne ◽  
Alaa El-Din Ahmed Bekhit
Keyword(s):  
Bioactive Compounds ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha
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