Genetic Models for Cyclic Dominance in Sockeye Salmon (Oncorhynchus nerka)

1992 ◽  
Vol 49 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Carl Walters ◽  
J. C. Woodey
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Large Fraction ◽  
Fishing Mortality ◽  
Age At Maturity ◽  
Dominant Trait ◽  
High Productivity ◽  
Cyclic Patterns ◽  
The Face ◽  
The Stability

A simple genetic mechanism may be partly responsible for maintaining violent cycles in abundance of some Fraser River sockeye salmon (Oncorhynchus nerka) stocks. If age at maturity is highly heritable, spawning runs in low cycle lines may have high percentages of age 5 spawners that tend to produce offspring that will return at age 5, due to production of low percentages of such spawners by preceding high cycle lines. Then even if each low cycle line has a high productivity per spawner, a large fraction of this productivity may be "lost" to the cycle line, in the form of age 5 recruits to other cycle lines. In the face of high fishing mortality, even a small relative loss from any cycle line may cause it to remain small relative to other lines. This model explains several observations, such as high productivity per spawner in low cycle lines, that cannot be explained by previous hypotheses involving depensatory predation or food supply. However, it is unlikely that genetic effects alone are responsible for the stability of cyclic patterns, unless low offcycle runs consist entirely of "temporal colonizer" genotypes that produce a high proportion of age 5 offspring as a dominant trait.

Estimating delayed density-dependent mortality in sockeye salmon (Oncorhynchus nerka): a meta-analytic approach

1997 ◽  
Vol 54 (10) ◽  
pp. 2449-2462 ◽  
Author(s):  
R A Myers ◽  
M J Bradford ◽  
J M Bridson ◽  
G Mertz
Keyword(s):  
Time Series ◽  
Sockeye Salmon ◽  
Analytical Approach ◽  
Oncorhynchus Nerka ◽  
Fishing Mortality ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Cyclic Patterns ◽  
Adult Abundance ◽  
Dependent Mortality

Delayed density-dependent mortality can be a cause of the cyclic patterns in abundance observed in many populations of sockeye salmon (Oncorhynchus nerka). We used a meta-analytical approach to test for delayed density dependence using 34 time series of sockeye data. We found no consistent evidence for delayed density-dependent mortality using spawner - spring fry or spawner-recruit data. We did find evidence for delayed density-dependent mortality at a 1 year lag for the spawner - fall fry and the spawner-smolt data; however, effects at lags greater than 1 year were weak and not statistically significant. Between-cohort interactions at a 1-year lag are not sufficient to cause the observed cycles in adult abundance, although they will tend to reinforce patterns established by other mechanisms. Our results imply that reductions in fishing mortality in off-peak years should result in an increase in abundance.

scholarly journals Simple dynamics underlie sockeye salmon (Oncorhynchus nerka) cycles

1998 ◽  
Vol 55 (10) ◽  
pp. 2355-2364 ◽  
Author(s):  
Ransom A Myers ◽  
Gordon Mertz ◽  
Jessica M Bridson ◽  
Michael J Bradford
Keyword(s):  
British Columbia ◽  
Density Dependence ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Stochastic Forcing ◽  
Stable Mode ◽  
Delayed Density Dependence ◽  
Cyclic Patterns ◽  
Ricker Model ◽  
Parameter Values

A variety of mechanisms have been proposed to explain the renowned British Columbia sockeye salmon (Oncorhynchus nerka) cycles, most of which invoke between-brood interactions (delayed density dependence) or depensatory harvest practices. We examine the dynamics of the Ricker model with realistic parameter values and suggest that the cycles could result from a stable mode excited by stochastic forcing. The previously proposed mechanisms are not required to generate cyclic patterns, although they could play a role in reinforcing cycles. Our results suggest that relaxing harvest rates will increase yields and decrease variability in sockeye abundances.

Simulation Studies of the Adams River Sockeye Salmon (Oncorhynchus nerka)

1971 ◽  
Vol 28 (10) ◽  
pp. 1493-1502 ◽  
Author(s):  
P. A. Larkin
Keyword(s):  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Narrow Range ◽  
Oncorhynchus Nerka ◽  
Large Fraction ◽  
Model System ◽  
Population Fluctuation ◽  
Simulation Studies ◽  
Predator Removal

The pattern of abundance of sockeye salmon (Oncorhynchus nerka) of the Adams River since 1938 is: 1 year large or "dominant," 1 year small or "subdominant," and 2 years very small or "off." In recent years, the subdominant run has shown indications of becoming as large as the dominant. This pattern can be accounted for by a model system in which predation is not sufficient to influence the dominant run, but predators, benefited by the abundance of prey, remove such a large fraction in the 3 succeeding years that the pattern is retained. Buffering of predation by the dominant run accounts for the larger size of the subdominant. Patterns similar in form to those observed naturally since 1922 are produced over a narrow range of parameters, and suggest that the particular circumstances of the Adams run are necessary to the nature of the population fluctuation, but are not so particular that some other pattern could not have emerged with a different sequence of environmental conditions. Taking an array of results of a series of simulations suggests that the odds of developing the existing pattern were about 50:50, although the subdominant run would more commonly become dominant as well by 1951, rather than as late as the 1960's. The double dominance situation is stable in the model system. In the present circumstances it seems appropriate to explore the possible benefits of managing the fishery so as to enhance the growth in size of the subdominant run, and perhaps to consider predator-removal programs to enable development of large runs on all 4 years of the traditional cycle.

Patterns of Interannual Variation in Age at Maturity of Sockeye Salmon (Oncorhynchus nerka) in Alaska and British Columbia

1985 ◽  
Vol 42 (10) ◽  
pp. 1595-1607 ◽  
Author(s):  
Randall M. Peterman
Keyword(s):  
British Columbia ◽  
Life Histories ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Comparative Approach ◽  
Age At Maturity ◽  
Bristol Bay ◽  
Freshwater Environment ◽  
Marine Life ◽  
Alternative Hypotheses

Interannual variations in mean age of maturity tend to be positively correlated among 10 stocks of sockeye salmon (Oncorhynchus nerka) which spawn in rivers emptying into Bristol Bay, Alaska. Taking a comparative approach, I utilized data from British Columbia and Alaska sockeye stocks with different life histories to test alternative hypotheses about sources of these variations in mean age at maturity. The hypotheses included freshwater environment, marine environment, and parental influences. Freshwater hypotheses were rejected and while some parental effects do exist, they are small compared with the effect of events in early marine life. Early marine growth rate data do not exist for these stocks but evidence from five other sockeye stocks shows that fast growth during this period tends to lead to earlier age at maturity.

Environmental and Parental Influences on Age at Maturity in Sockeye Salmon (Oncorhynchus nerka) from the Fraser River, British Columbia

1986 ◽  
Vol 43 (2) ◽  
pp. 269-274 ◽  
Author(s):  
Randall M. Peterman ◽  
Michael J. Bradford ◽  
Judith L. Anderson
Keyword(s):  
British Columbia ◽  
Age Structure ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Data Series ◽  
Fraser River ◽  
Age At Maturity ◽  
Long Term Effects ◽  
River Population ◽  
The Mean

Commercial fisheries possess the potential for applying strong selection on size or age at maturity in the populations they exploit. It is therefore important to know the extent to which these traits are inherited. We examined regressions of the mean age at maturity of cohorts of offspring on the mean ages of the female and male spawners which produced them for four populations of sockeye salmon (Oncorhynchus nerka) from the Fraser River, British Columbia. Unlike previous researchers, we found that neither genetic nor maternal effects are important, relative to environmental variables, in influencing year-to-year variation in age at maturity in these stocks. The differences between our findings and earlier ones are due to a longer data series and more complete population statistics than were available previously. We further analyzed the age structure of the Adams River population, which has a cyclic pattern of abundance. Fluctuating population density appeared to account for variation in age structure among cycle years in the Adams stock. We concluded that serious concerns about the long-term effects of size-selective fishing on mean age at maturity are probably not warranted for Fraser River sockeye.

Uncertainties in population dynamics and outcomes of regulations in sockeye salmon (Oncorhynchus nerka) fisheries: implications for management

2008 ◽  
Vol 65 (7) ◽  
pp. 1459-1474 ◽  
Author(s):  
Carrie A. Holt ◽  
Randall M. Peterman
Keyword(s):  
Sockeye Salmon ◽  
Management Practices ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Simulation Models ◽  
Age At Maturity ◽  
Sources Of Uncertainty ◽  
Future Assessment ◽  
Long Term Trends

Fisheries managers usually have multiple options available but are often unclear on how to choose among them owing to uncertainties in biological and management components of fisheries systems. We evaluated the performance of current and possible future assessment and management practices for sockeye salmon ( Oncorhynchus nerka ) in British Columbia and Alaska by using a computer model that included major biological and management components and their associated uncertainties (interannual variability in recruitment, age-at-maturity, and sex ratio, as well as uncertainty in observations of spawner abundances, forecasts of recruitment, and outcomes from implementing management regulations). One option for management practices that we evaluated was designed to make the forecasting model more realistic by accounting for long-term trends in age-at-maturity. A second option was designed to reduce deviations between management targets and actual or “realized” harvest levels. We found that compared with practices that ignore those sources of uncertainty, the second option produced annual catches that were higher, on average, and less variable over time while maintaining recruitment above critical conservation levels. Contrary to our expectations, the first modification did not result in comparable benefits. Our results demonstrate the value of using simulation models to evaluate potential modifications to Pacific salmon management practices.

Long-term trends in age-specific recruitment of sockeye salmon (Oncorhynchus nerka) in a changing environment

2004 ◽  
Vol 61 (12) ◽  
pp. 2455-2470 ◽  
Author(s):  
Carrie A Holt ◽  
Randall M Peterman
Keyword(s):  
Kalman Filter ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Oncorhynchus Nerka ◽  
Age At Maturity ◽  
Age Class ◽  
Sibling Models ◽  
Long Term Trends ◽  
Forecasting Errors

Sibling – age-class (sibling) models, which relate abundance of one age-class of adult sockeye salmon (Oncorhynchus nerka) to abundance of the previous age-class in the previous year, are commonly used to forecast abundance 1 year ahead. Standard sibling models assume constant parameters over time. However, many sockeye salmon populations have shown temporal changes in age-at-maturity. We therefore developed a new Kalman filter sibling model that allowed for time-varying parameters. We found considerable evidence for long-term trends in parameters of sibling models for 24 sockeye salmon stocks in British Columbia and Alaska; most trends reflected increasing age-at-maturity. In a retrospective analysis, the Kalman filter forecasting models reduced mean-squared forecasting errors compared with standard sibling models in 29%–39% of the stocks depending on the age-class. The Kalman filter models also had mean percent biases closer to zero than the standard models for 54%–94% of the stocks. Parameters of these sibling models are positively correlated among stocks from different regions, suggesting that large-scale factors (e.g., competition among stocks for limited marine prey) may be important drivers of long-term changes in age-at-maturity schedules in sockeye salmon.

Patterns of covariation in length and age at maturity of British Columbia and Alaska sockeye salmon (Oncorhynchus nerka) stocks

1999 ◽  
Vol 56 (6) ◽  
pp. 1046-1057 ◽  
Author(s):  
Brian J Pyper ◽  
Randall M Peterman ◽  
Michael F Lapointe ◽  
Carl J Walters
Keyword(s):  
British Columbia ◽  
Survival Rate ◽  
Body Length ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Oncorhynchus Nerka ◽  
Regional Scale ◽  
Survival Rates ◽  
Age At Maturity ◽  
Environmental Processes

We examined patterns of covariation in age-specific adult body length and in mean age at maturity among 31 sockeye salmon (Oncorhynchus nerka) stocks from western Alaska to southern British Columbia. Positive covariation in body length was prevalent across stocks of all regions (e.g., correlations (r) from 0.2 to 0.6), suggesting either that growth periods critical to final body length of sockeye salmon occur while ocean distributions of these stocks overlap or that large-scale environmental processes influence these stocks similarly while they do not overlap. We also found stronger covariation among body length of stocks within regions (r from 0.4 to 0.7), indicating that unique regional-scale processes were also important. Mean age at maturity also showed positive covariation both among and within regions, but correlations were weaker than those for length. We also examined patterns of covariation between length and mean age at maturity and between these variables and survival rate. Although length and mean age at maturity were negatively correlated, there was little evidence of covariation between these variables and survival rate, suggesting that environmental processes that influence marine survival rates of sockeye salmon are largely different from those affecting size and age at maturity.

Production of Fraser River sockeye salmon (Oncorhynchus nerka) in relation to decadal-scale changes in the climate and the ocean

1997 ◽  
Vol 54 (3) ◽  
pp. 543-554 ◽  
Author(s):  
R J Beamish ◽  
C-E M Neville ◽  
A J Cass
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Major Change ◽  
Fraser River ◽  
Climate Trends ◽  
High Productivity ◽  
The Pacific ◽  
Decadal Scale ◽  
Economic Expectations ◽  
General Response

The abundance of Fraser River sockeye salmon (Oncorhynchus nerka) stocks was low in the 1960s, increased to high levels in the 1980s, and possibly entered a period of low abundance in recent years. The abundance changes of the combined stocks can be separated into productivity regimes that correspond to changes in climate trends. The most distinct change occurred when there was a major change in the climate over the Pacific Ocean in the winter of 1976-1977. The existence of natural shifts in abundance trends means that the high returns that occur during periods of high productivity would not be expected to occur during the low-productivity periods. The response of Fraser River sockeye to climate changes may be a specific example of a more general response by a number of species of fishes in the Pacific and perhaps in other oceans. Because the shift from one regime to the other occurred quickly in the 1970s, future shifts could also occur quickly. It is necessary to detect natural shifts in productivity when attempting to manage fishing impacts to ensure that economic expectations are sound and that overfishing does not occur.

A Hypothesis of Alternation of Age of Return in Successive Generations of Skeena River Sockeye Salmon (Oncorhynchus nerka)

1971 ◽  
Vol 28 (4) ◽  
pp. 513-516 ◽  
Author(s):  
H. T. Bilton
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Female Parent ◽  
Juvenile Growth ◽  
Age At Maturity ◽  
Subsequent Growth ◽  
Initial Size ◽  
Egg Weight ◽  
Skeena River ◽  
Successive Generations

Egg weight of Scully Creek and Lower Babine River sockeye salmon (Oncorhynchus nerka) was positively correlated with length and, usually, age of the female parent. Egg weight was positively correlated with initial size and subsequent growth of juveniles, at least up to 3 months of age. Examination of scales indicated juvenile growth in the lake and ocean was inversely related to age at maturity. Hence it was hypothesized that the larger age 1.3 sockeye spawners tend to produce progeny that mature as smaller age 1.2 fish, which in turn give rise to progeny that mature as larger age 1.3 fish, and so on; an alternation in age of return of successive generations occurs.

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