scholarly journals Adaptive Control of Fishing Systems

1976 ◽  
Vol 33 (1) ◽  
pp. 145-159 ◽  
Author(s):  
Carl J. Walters ◽  
Ray Hilborn
Keyword(s):  
Sockeye Salmon ◽  
Optimization Methods ◽  
Fishing Effort ◽  
Model Parameters ◽  
Fraser River ◽  
The Face ◽  
Stock Recruitment ◽  
Best Fitting ◽  
Uncertainty Parameter ◽  
Recruitment Model

This paper discusses some formal techniques for deciding how harvesting policies should be modified in the face of uncertainty. Parameter estimation and dynamic optimization methods are combined for the Ricker stock-recruitment model to show how exploitation rates should be manipulated to give more information about the model parameters; in general, harvesting rates should be lower than would be predicted by the best fitting recruitment curve unless this curve predicts that the stock is very productive. A decision procedure is developed for comparing alternative stock-recruitment models; when applied to the Fraser River sockeye salmon (Oncorhynchus nerka), the procedure indicates that an experimental increase in escapements would be quite worthwhile. It appears that there is considerable promise for extending these methods and procedures to cases where the stock size is unknown and where fishing effort is poorly controlled.

scholarly journals Stock-recruitment models, principles of management and rules for regulating the fishery on the main Chukotka stocks of sockeye and chum salmon

2021 ◽  
Vol 201 (3) ◽  
pp. 735-751
Author(s):  
E. A. Shevlyakov ◽  
M. G. Feldman ◽  
A. N. Kanzeparova
Keyword(s):  
Sockeye Salmon ◽  
Chum Salmon ◽  
Fishery Management ◽  
Pacific Salmon ◽  
Far East ◽  
Simulation Models ◽  
Processing Capacity ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Recruitment Model

Fishery pressure on populations of pacific salmons has increased in the Rusian Far East in the last decade because of growing fishing and processing capacity, so measures for the fishery regulation are necessary, as the regime of pass days in rivers and marine coastal areas. Chukotka is now almost the only region where such restrictions are still absent. However, if the interest of fishery industry to the stocks of pacific salmon in Chukotka will grow, a successful scientifically based strategy of fishery should be developed to maintain exploitation of the stocks without exceeding the limits of excessive use. Year-to-year time series on spawning stock and recruitment of chum salmon in the Anadyr area and sockeye salmon in the Meynypilgyn area were analysed for development of recruitment models and establishment of general principles for adaptive fishery management. Nonlinear adaptive fishery management based on principles of buffer managing is proposed and tested under various regimes of landing using the stock simulation models accounting deviations from the standard stock-recruitment model. There is concluded that the level of exploitation is much lower than optimal for the Anadyr chum salmon, whereas escapement for spawning of the Meynypilgyn sockeye salmon should be increased in cases of low spawning stock of this species.

scholarly journals Influence of Selected Model Parameters on the Electromagnetic Levitation Melting Efficiency

2021 ◽  
Vol 11 (9) ◽  
pp. 3827
Author(s):  
Blazej Nycz ◽  
Lukasz Malinski ◽  
Roman Przylucki
Keyword(s):  
Electromagnetic Levitation ◽  
Optimization Methods ◽  
Calculation Model ◽  
Model Parameters ◽  
Starting Point ◽  
Low Efficiency ◽  
The Relationship ◽  
Reactive Metals ◽  
Electromagnetic Levitation Melting ◽  
Metal Melting

The article presents the results of multivariate calculations for the levitation metal melting system. The research had two main goals. The first goal of the multivariate calculations was to find the relationship between the basic electrical and geometric parameters of the selected calculation model and the maximum electromagnetic buoyancy force and the maximum power dissipated in the charge. The second goal was to find quasi-optimal conditions for levitation. The choice of the model with the highest melting efficiency is very important because electromagnetic levitation is essentially a low-efficiency process. Despite the low efficiency of this method, it is worth dealing with it because is one of the few methods that allow melting and obtaining alloys of refractory reactive metals. The research was limited to the analysis of the electromagnetic field modeled three-dimensionally. From among of 245 variants considered in the article, the most promising one was selected characterized by the highest efficiency. This variant will be a starting point for further work with the use of optimization methods.

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 Quirky patterns in time-series of estimates of recruitment could be artefacts

2014 ◽  
Vol 72 (1) ◽  
pp. 111-116 ◽  
Author(s):  
M. Dickey-Collas ◽  
N. T. Hintzen ◽  
R. D. M. Nash ◽  
P-J. Schön ◽  
M. R. Payne
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Meta Analysis ◽  
Reference Points ◽  
Fish Stocks ◽  
Stock Recruitment ◽  
Modelling Assumptions ◽  
Meta Analyses ◽  
Recruitment Model ◽  
Recruitment Time

Abstract The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.

Biochemical Studies on Sockeye Salmon During Spawning Migration: XI. The Free Histidine Content of the Tissues

1960 ◽  
Vol 17 (3) ◽  
pp. 347-351 ◽  
Author(s):  
J. D. Wood ◽  
D. W. Duncan ◽  
M. Jackson
Keyword(s):  
Amino Acid ◽  
Sockeye Salmon ◽  
Alimentary Tract ◽  
Oncorhynchus Nerka ◽  
The Other ◽  
Spawning Migration ◽  
Fraser River ◽  
Initial Value ◽  
Spawning Grounds ◽  
Biochemical Studies

During the first 250 miles (400 km) of spawning migration of Fraser River sockeye salmon (Oncorhynchus nerka) the free histidine content of the muscle, alimentary tract, and head+skin+bones+tail decreased to a small fraction of the initial value. A further decrease occurred in the levels of this amino acid in the alimentary tract during the subsequent 415-mile (657-km) migration to the spawning grounds, no change being observed with the other tissues. Comparatively small changes in free histidine were found with heart, spleen, liver, kidney and gonads during migration.

A widespread decrease in productivity of sockeye salmon (Oncorhynchus nerka) populations in western North America

2012 ◽  
Vol 69 (8) ◽  
pp. 1255-1260 ◽  
Author(s):  
Randall M. Peterman ◽  
Brigitte Dorner
Keyword(s):  
Sockeye Salmon ◽  
Spatial Scales ◽  
Oncorhynchus Nerka ◽  
Geographic Area ◽  
Fraser River ◽  
Western North America ◽  
Southeast Alaska ◽  
The Past ◽  
Large Geographic Area ◽  
Marine Areas

We used data on 64 stocks of sockeye salmon ( Oncorhynchus nerka ) from British Columbia (B.C.), Washington, and Alaska to determine whether recent decreases in abundance and productivity observed for Fraser River, B.C., sockeye have occurred more widely. We found that decreasing time trends in productivity have occurred across a large geographic area ranging from Washington, B.C., southeast Alaska, and up through the Yakutat peninsula, Alaska, but not in central and western Alaska. Furthermore, a pattern of predominantly shared trends across southern stocks and opposite trends between them and stocks from western Alaska was present in the past (1950–1985), but correlations have intensified since then. The spatial extent of declining productivity of sockeye salmon has important implications for management as well as research into potential causes of the declines. Further research should focus on mechanisms that operate at large, multiregional spatial scales, and (or) in marine areas where numerous correlated sockeye stocks overlap.

The Influence of Climate on the Stock and Recruitment of Pink and Sockeye Salmon from the Fraser River, British Columbia, Canada

2004 ◽  
Vol 133 (6) ◽  
pp. 1396-1412 ◽  
Author(s):  
R. J. Beamish ◽  
J. T. Schnute ◽  
A. J. Cass ◽  
C. M. Neville ◽  
R. M. Sweeting
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Fraser River ◽  
Stock And Recruitment

Optimum Escapements in the Face of Alternative Recruitment Hypotheses

1981 ◽  
Vol 38 (6) ◽  
pp. 678-689 ◽  
Author(s):  
Carl J. Walters
Keyword(s):  
Dynamic Programming ◽  
Adaptive Management ◽  
Stochastic Models ◽  
Value Of Information ◽  
Fishery Management ◽  
Historical Experience ◽  
Active Probing ◽  
Adaptive Policy ◽  
The Face ◽  
Stock Recruitment

Available data are often inadequate to discriminate among alternative models that make different predictions about the consequences of allowing escapements outside the range of recent historical experience. Dynamic programming is used to show that the optimum policy in such situations can involve active probing or experimentation with escapements. The optimum adaptive policy is usually difficult to compute, but generally may be closely approximated by a "Bayes equivalent" policy that is simpler to estimate but does not account explicitly for the value of information associated with allowing more extreme escapements. While there are various practical difficulties in estimating and implementing an optimum policy, it is concluded that regular probing experiments should be included in every fishery management plan.Key words: stock-recruitment, optimization, adaptive management, stochastic models

Population Dynamics of the Arcto-Norwegian Cod

1967 ◽  
Vol 24 (1) ◽  
pp. 145-190 ◽  
Author(s):  
D. J. Garrod
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Group Iii ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Post War ◽  
The One ◽  
Definition Of

By reason of its geographical distribution, the Arcto-Norwegian cod (Gadus morhua) supports three distinct fisheries, two feeding fisheries in the Barents Sea and at Bear Island–Spitsbergen, and a spawning fishery off the Norway coast. In the past this diversity of fishing on the one stock has made it difficult to unify all the data to give an overall description of post-war changes in the stock. In this contribution three modifications of conventional procedures are introduced which enable this to be done. These are: (i) a system of weighting the catch per unit effort data from each fishery to a level of comparability; (ii) a more rigorous definition of the effective fishing effort on each age-group; (iii) a method of estimation of the effective fishing effort on partially recruited age-groups.Using these methods the analysis presents the effects of fishing on each fishery in the context of its effect on the total stock, and at the same time it indicates ways in which factors other than fishing may have influenced the apparent abundance of the stock. The treatment of the data is also used to derive estimates of spawning stock and recruitment of 3-year-old cod for subsequent analysis of stock–recruitment relationships.

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