Application of Bayesian decision analysis to management of a sockeye salmon (Oncorhynchus nerka) fishery

1998 ◽  
Vol 55 (1) ◽  
pp. 86-98 ◽  
Author(s):  
Christina A Robb ◽  
Randall M Peterman
Keyword(s):  
Decision Analysis ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Data Uncertainty ◽  
Optimal Decision ◽  
Management Decision ◽  
Bayesian Decision ◽  
Stock Recruitment ◽  
Salmon Stock ◽  
Parameter Values

We developed a decision-making framework for management of a sockeye salmon (Oncorhynchus nerka) fishery on the Nass River, British Columbia, that explicitly accounts for uncertainties in (i) the stock-recruitment relationship, (ii) annual recruitment, (iii) run timing, and (iv) catchability. The method used Monte Carlo simulation within a decision analysis framework and used Bayesian statistics to calculate probabilities for parameter values in the Shepherd stock-recruitment model. The decision dealt with when to open a fishery, upstream of all normal fishing areas, that is intended to harvest fish that are considered surplus to spawning requirements. The optimal decision rule for opening this fishery depended on (i) the relative importance of different management objectives and (ii) the range of shapes of the stock-recruitment relationship that were admitted as possible within the decision analysis. The management decision that was optimal if we assumed a dome-shaped stock-recruitment relationship was not optimal when we admitted the possibility of other shapes of the relationship. Therefore, given the variability in salmon stock-recruitment data, uncertainty in the shape of the stock-recruitment relationship should be routinely considered in analyses of management decisions.

A Bayesian decision analysis to set escapement goals for Fraser River sockeye salmon (Oncorhynchus nerka)

2000 ◽  
Vol 57 (5) ◽  
pp. 962-979 ◽  
Author(s):  
Jon T Schnute ◽  
Al Cass ◽  
Laura J Richards
Keyword(s):  
Decision Analysis ◽  
Sockeye Salmon ◽  
Policy Design ◽  
Oncorhynchus Nerka ◽  
Active Role ◽  
Analytical Framework ◽  
Policy Outcomes ◽  
Fraser River ◽  
Policy Options ◽  
Bayesian Decision

This paper illustrates a complete Bayesian decision analysis for evaluating multistock harvest goals in the fishery on Fraser River sockeye salmon (Oncorhynchus nerka). We identify four key steps necessary to assess a resource production system. Each step entails choices that can alter the perceived consequences of management decisions. A Markov chain Monte Carlo sample captures uncertainty in the population dynamics. The Bayesian formalism then translates this uncertainty into uncertain policy outcomes. We examine a relatively simple control law, designed to protect stocks at low abundance. We restrict our attention to retrospective policy analysis by investigating what might have happened to sockeye stocks if management had proceeded differently during years for which historical data are available. A formal objective function quantifies societal values associated with a range of policy options. To confine the paper to manageable scope, we consider only relatively simple assumptions. Our analytical framework offers an iterative route to policy design, where managers play an active role in formulating policy options and evaluating their consequences.

Alternative Recruitment Models of Adams River Sockeye Salmon, Oncorhynchus nerka

1987 ◽  
Vol 44 (9) ◽  
pp. 1551-1561 ◽  
Author(s):  
Jeremy S. Collie ◽  
Carl J. Walters
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Status Quo ◽  
Management Policy ◽  
Best Management ◽  
Interaction Terms ◽  
Ricker Model ◽  
The Status ◽  
Stock Recruitment ◽  
High Yields

Despite evidence of depensatory interactions among year-classes of Adams River sockeye salmon (Oncorhynchus nerka), the best management policy is one of equal escapement for all year-classes. We fit alternative models (Ricker model and Larkin model) to 32 yr of stock–recruitment data and checked, using simulation tests, that the significant interaction terms in the Larkin model are not caused by biases in estimating the parameters. We identified a parameter set (Rationalizer model) for which the status quo cyclic escapement policy is optimal, but this set fits the observed data very poorly. Thus it is quite unlikely that the Rationalizer model is correct or that the status quo escapement policy is optimal. Using the fitted stock–recruitment parameters, we simulated the sockeye population under several management policies. The escapement policy optimal under the Ricker model is best overall because of the high yields if it should be correct. If the three stock–recruitment models are equally likely to be correct, the simulations predict that adopting a constant-escapement policy would increase long-term yield 30% over the current policy and that an additional 15% increase in yield could be obtained if the policy were actively adaptive.

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.

Model of Salmon Age Structure and Its Use in Preseason Forecasting and Studies of Marine Survival

1982 ◽  
Vol 39 (11) ◽  
pp. 1444-1452 ◽  
Author(s):  
Randall M. Peterman
Keyword(s):  
Survival Rate ◽  
Density Dependence ◽  
Age Structure ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Spawning Areas ◽  
Forecasting Method ◽  
Salmon Stock ◽  
Marine Survival ◽  
Stock Abundance

A method is derived to determine whether ocean abundance of a salmon stock affects either the survival rate between particular ages or the proportion of the ocean population which migrates back to freshwater spawning areas. The approach, similar to Fredin's smolt indices method, uses data on brood-year contributions to adult returns in successive years. Survival rate and proportion maturing are found to be independent of stock abundance after age 3, except in Naknek River sockeye (Oncorhynchus nerka) data. In cases such as Babine Lake sockeye salmon, where nonlinearity has been identified previously in the relation between smolt abundance and total adult returns, this lack of density dependence in the older ages means that the mortality processes which cause that nonlinearity act early in smolt life. The relations between abundance of adult returns of age n in year t and returns of age n + 1 from the same brood class in year t + 1 are useful as preseason forecasting techniques. The method derived here, which uses logarithms of abundances, improves upon the existing forecasting method. Deviations from the relation between abundances of brood-year returns can in some cases be explained by smolt weight, which is shown to affect mean age at return.Key words: salmon age structure, marine survival, age-at-return, smolt weight, preseason forecasting

Empirical and theoretical analyses of correction of time-series bias in stock-recruitment relationships of sockeye salmon (Oncorhynchus nerka)

1995 ◽  
Vol 52 (10) ◽  
pp. 2174-2189 ◽  
Author(s):  
Josh Korman ◽  
Randall M. Peterman ◽  
Carl J. Walters
Keyword(s):  
Time Series ◽  
Least Squares ◽  
Bias Correction ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Empirical Relationship ◽  
Estimation Method ◽  
Estimation Methods ◽  
Theoretic Approach ◽  
Stock Recruitment

Using data from 30 sockeye salmon (Oncorhynchus nerka) stocks and Monte Carlo simulations, we examined the importance of time-series bias on estimates of optimal harvest rate, optimal escapement, and sustainable yield. We compared the performance of the least-squares procedure for fitting a Ricker curve with an existing bias-correction method. Simulations showed that the effect of time-series bias is greatest for low-productivity stocks that exhibit a high degree of autocorrelation among residuals of the stock-recruitment relationship. A strong inverse empirical relationship between autocorrelation and stock productivity among the 30 stocks suggests that time-series bias is a more important concern for low-productivity northern stocks than for more productive southern stocks. The corrected method reduced bias in optimal escapement estimates under a limited set of conditions but at the price of increased variance in the estimates. For a constant escapement goal policy, using the bias correction thus resulted in sustainable yields slightly lower than or equal to expected values for 28 of the 30 stocks compared with yields obtained using the standard least-squares estimation method. We demonstrate the value of using a decision theoretic approach to evaluate the performance of estimation methods.

scholarly journals Effects of marine-derived nutrients on population dynamics of sockeye salmon (Oncorhynchus nerka)

2008 ◽  
Vol 65 (8) ◽  
pp. 1635-1648 ◽  
Author(s):  
Tadayasu Uchiyama ◽  
Bruce P. Finney ◽  
Milo D. Adkison
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Isotope Analysis ◽  
Juvenile Salmon ◽  
Juvenile Survival ◽  
Water Residence Time ◽  
Nitrogen Stable Isotope ◽  
Factors Affecting ◽  
Stock Recruitment ◽  
Marine Derived Nutrients

The effects of marine-derived nutrients (MDN) on the productivity of sockeye salmon ( Oncorhynchus nerka ) stocks in Alaska, USA, were examined through nitrogen stable isotope analysis of smolts and mathematical models of the sockeye stock–recruit relationship. Smolt δ15N was used to infer the degree to which smolts depend on MDN for their growth. We found that characteristics of sockeye nursery lakes and watersheds significantly affected the availability of MDN to juvenile sockeye. The magnitude of escapement and water residence time were the most important factors affecting the MDN availability to juvenile salmon. Analysis of stock–recruit models indicated that regional environmental fluctuations had a large effect on stock productivities. However, stock–recruitment data showed little evidence that increasing MDN input to nursery lakes increased stock productivities. Stock–recruitment data may be poorly suited to detection of the influence of MDN because of the multitude of factors that influence juvenile survival in the first several years of their life.

Epistemic Uncertainties in Decision Making

2005 ◽  
Author(s):  
Michael Havbro Faber ◽  
Marc A. Maes
Keyword(s):  
Decision Making ◽  
Decision Analysis ◽  
Optimal Decision ◽  
Bayesian Decision ◽  
Typical Situation ◽  
Controversial Problem ◽  
Optimal Decision Making ◽  
Definition Of ◽  
Assessment Problems

The present paper reviews and outlines the interpretation of uncertainties with a view to the various different categorizations introduced in the literature. A framework is then presented for risk based decision making taking basis in the Bayesian decision theory and recent methodical developments in risk assessment. It is emphasized that in principle all types of uncertainties should be included in formal decision analysis and that not doing so corresponds to informal decision analysis the quality of which may be difficult to judge. The controversial problem in engineering decision making of how to take into account uncertainties associated with the definition of the system being analyzed is outlined. For the typical situation where a discrete set of possible system representations is possible it is shown how a decision problem may be formulated for the identification of the optimal system to be considered as basis for decision making. The presented decision framework takes into account all prevailing uncertainties, epistemic as well as aleatory. Examples related to structural design and assessment problems relevant for offshore engineering are given illustrating how not to account for all types of uncertainties leads to sub-optimal decision making.

Cyclic Dominance and Optimal Escapement of Adams River Sockeye Salmon (Oncorhynchus nerka)

1990 ◽  
Vol 47 (4) ◽  
pp. 838-849 ◽  
Author(s):  
D. W. Welch ◽  
D. J. Noakes
Keyword(s):  
Sockeye Salmon ◽  
Net Present Value ◽  
Oncorhynchus Nerka ◽  
Total Yield ◽  
Confidence Regions ◽  
Parameter Estimates ◽  
Magnitude Comparison ◽  
Ricker Model ◽  
Stock Recruitment ◽  
Potential Benefits

We examined escapement policies for a stock-recruitment model with negative between-year interactions. Regardless of the degree of interaction present, the optimal policy is to always equalize escapement. Parameter estimates obtained for the Adams River sockeye salmon (Oncorhynchus nerka) indicate that between-year interactions may occur, but confidence regions include the null hypothesis of no interaction at all (the Ricker model). We conclude that the extreme amplitude of the current recruitment cycle in this stock frustrates statistical identification of interaction. It seems unlikely that between-year interactions will be measurable until the off year runs increase by at least two to three orders of magnitude. Comparison of total yields for the Adams River sockeye shows that an equal escapement policy could increase yields by at least 35% over that obtained by the current cyclic escapement pattern. This is equivalent to obtaining an additional $27 million in total yield per annum from the Adams River stock alone and, assuming a discount rate of 4%, translates into an increase in net present value of $675 million. If between-year interactions do not exist, the potential benefits of moving to an equal escapement policy are even larger, on the order of $3 to $4 billion.

A Note on Variability of Marine Survival of Sockeye Salmon (Oncorhynchus nerka) and Effects of Flooding on Spawning Success

1987 ◽  
Vol 44 (10) ◽  
pp. 1791-1795 ◽  
Author(s):  
Richard E. Thorne ◽  
James J. Ames
Keyword(s):  
Sockeye Salmon ◽  
River Flow ◽  
Oncorhynchus Nerka ◽  
Major Effect ◽  
Flow Conditions ◽  
Annual Variability ◽  
Lake Washington ◽  
Salmon Stock ◽  
Marine Survival ◽  
Spawning Success

Most of the annual variability in sockeye salmon (Oncorhynchus nerka) survival has been assumed to be associated with freshwater stages, while marine survival has been assumed to be very consistent from year to year. Data from Lake Washington sockeye salmon stock, including hydroacoustic surveys of presmolt populations, indicate that marine survival may vary on the order of 4–20%. However, the data also show that river flow conditions during spawning and gravel incubation have a major effect on production for this stock.

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