MIXED-STOCK VS. TERMINAL FISHERIES: A BIOECONOMIC MODEL

ABSTRACT. This paper develops a bioeconomic model of a fishery conducted on several stocks, a large stock capable of supporting a commercial fishery, and one or more smaller stocks which could be driven to extinction at harvest rates that the larger stock can sustain. The model permits a shifting of effort from a mixed-stock fishery to single-stock fisheries. Such a shift could save the weaker stocks from extinction, but the model highlights economic incentives to reject this option. This points to a fundamental conflict between the preservation of biodiversity and economic pressures to maximize profits. This fundamental conflict has in turn important consequences in current debates over the restructuring of major fisheries including those directed at Pacific salmon.     

OPTIMAL-SUSTAINABLE MANAGEMENT OF MULTI-SPECIES FISHERIES: LESSONS FROM A PREDATOR-PREY MODEL

ABSTRACT. In this paper we consider the meaning of sustainable resource management in multi-dimensional resources. Based on the principle of intergenerational fairness, we define fisheries management as sustainable if it does not lead to a decline in the net present value of the fishery. If sustainability, or intergenerational fairness, were held as an obligation by fishery managers, then the traditional present-value maximization objective would be constrained. Using numerical solutions to a simple predator-prey model, we explore how the optimal-sustainable management of this fishery would differ from management that seeks to maximize the present value of the benefits. General lessons regarding the meaning of sustainable fishery management are discussed.     

STEADY STATE AND INTERTEMPORAL MANAGEMENT MODELS FOR MARINE FISHERIES

Abstract Steady state and dynamic management models are developed for analyzing the Malaysian marine fisheries. These models originate from the theoretical concepts of the natural resource economics namely the open access, limited entry and the intertemporal fishery models. Such management models are deemed necessary because of the need to sustain the depleting resource and degrading environment. Marine fisheries had been managed under open access for a long time before government intervention took effect sometime during the 1960s. Open access and government intervention during the earlier phase of economic development contributed to the immediate pressure on fisheries. Community development programs geared to alleviate poverty among the fishermen apparently contradicted the effort of sustaining fisheries. Even today this fundamental management objective of sustainable development of fishery resource is not fully adhered to. This study suggests that ability to sustain fishery requires government intervention that can direct resource use to steady state or intertemporal optimal levels.     

CLIMATE CHANGE AND FISHERIES: ASSESSING THE ECONOMIC IMPACT IN ICELAND AND GREENLAND

ABSTRACT. . Climate changes in the 21st century are expected to significantly increase ocean temperatures and modify other oceanographic conditions in the North Atlantic. Marine biological research suggests that the impacts on the commercially most important fish stocks in the Icelandic‐Greenland ecosystem may well be quite substantial. This will obviously lead to a corresponding impact on the economies of these two countries. However, the timing, extent and biological impact of global warming is quite uncertain. As a result the economic impact is similarly uncertain. This paper attempts to provide estimates of the impact of altered fish stocks due to global warming on the Icelandic and Greenland economies. The approach is one of stochastic simulations. This involves essentially three steps. The first is to obtain predictions of the impact of global warming on fish stocks and the associated probability distribution. For this we rely on recent marine biological predictions. The second step is to estimate the role of the fisheries sector in the two economies. This is done with the help of modern econometric techniques based on economic growth theory and historical data. Obviously these estimates are also subject to stochastic errors and uncertainty. The third step is to carry out Monte Carlo simulations on the basis of the above model and the associated uncertainties. The result of the Monte Carlo simulations consists of a set of dynamic paths for GDP over time with an expected value and a probability distribution for each future year. On this basis it is possible to calculate confidence intervals for the most likely path of GDP over time. The results indicate that the fisheries impact of global warming on the Icelandic GDP is more likely to be positive than negative but unlikely to be of significant magnitude compared to historical economic growth rates and fluctuations. The uncertainty of this prediction, however, is large. For Greenland, the impact on fish stocks and the GDP is highly likely to be positive and quite substantial relative to the current GDP. Due to less knowledge of the relationship between the fisheries sector and the Greenland economy, however, the confidence interval of this prediction is even wider than in the case of Iceland.     

MODELS FOR COOPERATION AND CONSPIRACY IN FISHERIES: CHANGING THE RULES OF THE GAME

Fisheries regulation is considered necessary to counteract the effects of competitive forces which can lead to a “tragedy of the commons”. Yet management initiatives have often failed because they did not take into account competitive responses of fishing enterprises. In particular, open access fisheries provide strong incentives for the development of excessive harvesting capacity. This in turn leads to harvesting that is concentrated in space and time, with adverse effects on both the resource and markets. A coalition of fishermen, such as a fishermen's cooperative, has interests similar to those of a sole owner, and thus would be expected to produce more efficient behaviour. In practice, however, fishermen's cooperatives seldom persist. Game theory is used to explore relationships between the coalition structure of the industry, economic variables, and regulation. The models are based loosely on a purse seine fishery for herring. The results suggest that the potential to form stable coalitions is affected by changes in price and harvest. Changes in regulation also affect stability of coalitions. When interpreted in the light of historical changes in the herring fishery, these results suggest that industry may not accept regulations which do not permit formation of stable coalitions.     

RUMINATIONS ON THE DEVELOPMENT AND FUTURE OF POPULATION DYNAMICS MODELS IN FISHERIES

ABSTRACT. I trace the development of fisheries models (i.e., fish population dynamics models of species subject to fisheries) to the 21st century. The first real efforts occurred in the period 1900 1920 with the work of Baranov (the “Grandfather” of fisheries population dynamics) and the formation of the International Council for the Exploration of the Sea (ICES). The establishment of the science occurred between 1920 1960 with multi‐species modeling, age‐ and size‐structure dynamics, and production models. Fundamental work during this time was done by Ricker (the “Father” of fisheries population dynamics), Beverton and Holt (the “Prophets” of fisheries population dynamics), Chapman, Dickie, DeLury, Graham, Gulland, Leslie, Lotka and Volterra, Russell, Schaefer, and Thompson. During this time, most of the workwas deterministic and mathematical. Between 1960 and 1980, statistical methodology evolved greatly but was separate from mathematical advances for the most part. The development of statistical principles for the estimation of animal abundance was further enhanced by Arnason, Buckland, Burnham and Anderson and White, Cormack, Eberhardt, Jolly, Manly, Pollock, Ricker, Robson, and Seber, among others. Fisheries models evolved in a deterministic setting, with advances in age‐structured models (Gulland, Pope, Doubleday), surplus production models (Pella, Tomlin‐son, Schnute, Fletcher, Hilborn), growth models, bioeconomic models (C. Clark) and management control models (Hilborn, Walters). The period 1980 2000 was the Golden Age. The integration between mathematics and statistics occurred when likelihood and least squares techniques were formally combined with mathematical models of population change. The number of fisheries modelers grew exponentially during this time, resulting in a concomitant increase in publications. A major advance in the 1990s has been the development of Bayesian and time series methods, which have allowed explicit specification of uncertainty. Currently, theory allows realistic modeling of age‐ and size‐structured populations, migratory populations and harvesting strategies. These models routinely incorporate measurement error, process error (stochasticity) and time variation. But data needs often overwhelm the performance of models, and greater demands are being placed on models to answer complex questions. There has been poor communication between fisheries and ecological modelers, between fisheries researchers and statisticians, and among fisheries researchers in different geographic locales. Future models will need to deal better with habitat and spatial concerns, genetics, multispecies interactions, environmental factors, effects of harvesting on the ecosystem, model misspecification and so‐cioeconomic concerns. Meta‐analysis, retrospective analysis and operating models are some modern approaches for dealing with uncertainty and providing for sustainable fisheries. However, I fear that current attacks on single‐species models and management may result in rejection of these advances and an attempt to substitute a less scientific approach.     

MODELING CLIMATE CHANGE AND THE EFFECT ON THE NORWEGIAN SALMON FARMING INDUSTRY

Abstract Global warming is expected to affect the ecosystem in the Northeast Atlantic, and substantial changes will also affect the aquaculture industry. Farming of salmon and trout is the biggest aquaculture industry in Norway, with an export value of about 3 billion US dollars in 2007. The objective of the paper is to analyze the potential economic effect a general increase in sea temperature can have on the Norwegian salmon aquaculture industry. The assessment of the economic impact of global warming is made possible by estimating a growth function, which explicitly includes sea water temperature. The analysis compares the economic effect of a climate change on fish farming plants in the south and the north of Norway. The scenarios are based on a model with monthly seasonal variation in temperature.     

SUSTAINABLE YIELDS IN FISHERIES: UNCERTAINTY,RISK‐AVERSION,AND MEAN‐VARIANCE ANALYSIS

Abstract We consider a model of a fishery in which the dynamics of the unharvested fish population are given by the stochastic logistic growth equation Similar to the classical deterministic analogon, we assume that the fishery harvests the fish population following a constant effort strategy. In the first step, we derive the effort level that leads to maximum expected sustainable yield, which is understood as the expectation of the equilibrium distribution of the stochastic dynamics. This replaces the nonzero fixed point in the classical deterministic setup. In the second step, we assume that the fishery is risk averse and that there is a tradeoff between expected sustainable yield and uncertainty measured in terms of the variance of the equilibrium distribution. We derive the optimal constant effort harvesting strategy for this problem. In the final step, we consider an approach that we call the mean‐variance analysis to sustainable fisheries. Similar as in the now classical mean‐variance analysis in finance, going back to Markowitz [1952] , we study the problem of maximizing expected sustainable yields under variance constraints, and with this, minimizing the variance, e.g., risk, under guaranteed minimum expected sustainable yields. We derive explicit formulas for the optimal fishing effort in all four problems considered and study the effects of uncertainty, risk aversion, and mean reversion speed on fishing efforts.     

RANDOM PENALTIES AND RENEWABLE RESOURCES: A MECHANISM TO REACH OPTIMAL LANDINGS IN FISHERIES

Abstract Recent literature considers illegal landings a moral hazard problem that arises because individual landings are unobservable. The literature proposes incentive schemes to solve the information problem. However, most of the proposed schemes raise huge information requirements and social budget balance is not secured. In this paper, we suggest a random penalty mechanism that reduces the information requirements and secures budget balance in the case of a given number of licensed vessels. In the random penalty mechanism, aggregate landings are measured through stock sizes and the natural growth function. If aggregate landings are below optimal landings, each fisherman receives a subsidy. If aggregate catches are above optimal landings, the mechanism works such that either the fisherman is randomly selected and pays a fine or the fisherman is not selected and receives a subsidy. The fine and subsidy can be designed such that budget balance is secured. Provided risk aversion is sufficiently large and the fine is high enough, the random penalty mechanism will generate optimal individual landings. The budget balance combined with risk aversion drives the result for this advanced tax/subsidy system that does not exhaust the resource rents. The budget balance creates interdependence between fishermen that secure optimality.     

ON DEVELOPMENT,FISHERIES AND DYNAMITE: A BRIEF REVIEW OF TROPICAL FISHERIES MANAGEMENT

Some features of underdevelopment in Third World countries are reviewed with emphasis on their impact on fisheries and fisheries management. Poverty in rural communities is highlighted as the key issue preventing rational management of tropical inshore fisheries and shown to be - along with (misguided) export-oriented development strategies - the root cause for destructive fishing techniques and environmental degradation. Some implications for modelling are outlined. A reorientation of investments towards job creation in fish-erfolk and other rural communities is advocated as the key aspect of any solution of fisheries problems in Third World countries.     

ECONOMIC IMPACTS OF GLOBAL WARMING: THE CASE OF THE BARENTS SEA FISHERIES

ABSTRACT. . Regional analyses of possible physical and biological effects of global warming in the Barents Sea area have been carried out recently. Based on such studies possible economic impacts of global warming on the Barents Sea fisheries have been quantified, assuming different types of management regimes. The EconSimp2000 model, consisting of the ecosystem model AggMult and the fleet model EconMult have been parameterized based on fleet and catch records from the Norwegian Barents Sea fisheries. The model has been used to study biological and economic impacts of different environmental scenarios representing possible consequences of global warming. The current environmental situation, including normal seasonal and other variations, has been used as a reference scenario. Several biological and economic indicators have been defined in order to evaluate the simulation results of different environmental scenarios and different types of management regimes. The findings support earlier studies where biological and economic impacts of changes in management regime is found to be more pronounced than impacts caused by effects of global warming.     

PARADIGM SHIFTS IN FISHERIES STOCK ASSESSMENT: FROM INTEGRATED ANALYSIS TO BAYESIAN ANALYSIS AND BACK AGAIN

ABSTRACT. I describe integrated analysis and Bayesian analysis, which have been two of the most influential paradigms in fisheries stock assessment during the last two decades of the twentieth century. These two paradigms have generally been considered complementary, rather than competing. However, recent advances in integrated analysis, including the special case of meta‐analysis, have made Bayesian analysis somewhat redundant. I describe how data used to create priors for use in Bayesian analysis can be integrated directly into the analyses. This provides a much more convenient way of accurately including the information and associated uncertainty into the analyses. I discuss how there is still a need to describe the uncertainty and suggest that research should focus on the most appropriate methods for doing this.     

ESTIMATION OF SALMON ESCAPEMENT: MODELS WITH ENTRY,MORTALITY AND STOCHASTICITY

Understanding the dynamics of Prince William Sound pink salmon requires knowledge of the size of the spawning population in a stream over time. Periodic aerial surveys provide observations on the number of spawners, but the lack of daily observations requires a model to fill in the gaps. We develop a differential equation framework to represent the dynamics of escapement during the season. An exponential population growth model with a time-varying rate of growth is used for the number of spawners. The rate of growth consists of two primary components: the entry of salmon to the stream (escapement) and the mortality of spawners in the stream. The models for entry and mortality are also functions of time. The stochastic element of the model is based on a nonhomogeneous birth-and-death process which leads to a least squares estimation approach with either additive measurement or process errors. We illustrate the approach for a stream in Prince William Sound by fitting various models to observed spawner abundance, mortality counts from ground surveys and weir counts of the entry to the stream. We believe this approach could improve salmon escapement estimation, because the processes governing entry and mortality are explicitly considered.     

A PREDICTIVE MODEL TO INFORM ADAPTIVE MANAGEMENT OF DOUBLE‐CRESTED CORMORANTS AND FISHERIES IN MICHIGAN

The proliferation of double‐crested cormorants (DCCOs; Phalacrocorax auritus) in North America has raised concerns over their potential negative impacts on game, cultured and forage fishes, island and terrestrial resources, and other colonial water birds, leading to increased public demands to reduce their abundance. By combining fish surplus production and bird functional feeding response models, we developed a deterministic predictive model representing bird–fish interactions to inform an adaptive management process for the control of DCCOs in multiple colonies in Michigan. Comparisons of model predictions with observations of changes in DCCO numbers under management measures implemented from 2004 to 2012 suggested that our relatively simple model was able to accurately reconstruct past DCCO population dynamics. These comparisons helped discriminate among alternative parameterizations of demographic processes that were poorly known, especially site fidelity. Using sensitivity analysis, we also identified remaining critical uncertainties (mainly in the spatial distributions of fish vs. DCCO feeding areas) that can be used to prioritize future research and monitoring needs. Model forecasts suggested that continuation of existing control efforts would be sufficient to achieve long‐term DCCO control targets in Michigan and that DCCO control may be necessary to achieve management goals for some DCCO‐impacted fisheries in the state. Finally, our model can be extended by accounting for parametric or ecological uncertainty and including more complex assumptions on DCCO–fish interactions as part of the adaptive management process.     

FISHERIES SCIENCE AND MODELING: A LOOK TO THE FUTURE

In this paper I forecast that the fisheries management problems we face as we enter the twenty-first century will have less to do with extractive conservation and more to do with protection of regional and global environments. I present two contemporary fisheries management case histories which tend to bear this out: (1) Pacific Northwest salmon, with particular reference to the Columbia River, and (2) the high-seas driftnet fisheries of the North Pacific. Characterizing these types of problems in a few words, I would say that their effects are long-term and perhaps irreversible, and that they lead to conditions that we have yet to experience. Because of the type of input needed from the scientific community in order to forge rational solutions, modeling becomes ever more important in translating scientific experience into a form that will enlighten and move decisionmakers.     

THE FAO PRECAUTIONARY APPROACH AFTER ALMOST 10 YEARS: HAVE WE PROGRESSED TOWARDS IMPLEMENTING SIMULATION‐TESTED FEEDBACK‐CONTROL MANAGEMENT SYSTEMS FOR FISHERIES MANAGEMENT?

ABSTRACT. It is almost ten years since the FAO Technical Consultation on the Precautionary Approach to Capture Fisheries took place in Lysekil, Sweden. One outcome from this Technical Consultation was a set of guidelines on the precautionary approach to capture fisheries and species introductions. These guidelines include the need to incorporate harvest control rules in management plans. Harvest control rules should specify what action is to be taken when specified deviations from the operational targets and constraints are observed. The specification should include minimum data requirements for the types of assessment methods to be used for decision‐making. Combinations of harvest control rules, assessment methods and data collection schemes are referred to as management procedures. It is now well‐recognized that using management procedures is likely to lead to improved conservation of fishery resources, and that they should be evaluated to assess whether they are likely to achieve the goals for fishery management given the types of uncertainties that are likely to frustrate this venture. In general, evaluation of management procedures has been based on simulation modeling. This paper reviews the progress that has been made in various fisheries jurisdictions in terms of implementing management procedures, and why and where it has proved difficult or even impossible to implement management procedures.     

COMPARING PROACTIVE AND REACTIVE MANAGEMENT: MANAGING A TRANSBOUNDARY FISH STOCK UNDER CHANGING ENVIRONMENT

Environmental change in general, and climate change in particular, can lead to changes in distribution of fish stocks. When such changes involve transboundary fish stocks, the countries sharing the stock need to reconsider their harvesting policies. We investigate the effects of changing stock distribution on the optimal fishing policies in a two players’ noncooperative game. We compare reactive management, under which the manager ignores future distributional shifts (knowingly or unknowingly), with proactive management where the manager considers such shifts in his decisions. A dynamic programming model is developed to identify closed‐loop Nash strategies. We show that the role of two players is symmetric under reactive management but asymmetric under proactive management where managers anticipate future changes in stock ownership. The player losing the stock tends to harvest more aggressively compared to the player gaining the stock who acts more conservatively. Strategic interactions show tendency for complementary actions that can change abruptly during the ownership transition. The differences between management regimes vary from quantitative to qualitative; differences are minimal for stocks with little or no schooling, whereas highly schooling stocks may avoid collapse only under proactive management.     

SHARING THE BENEFITS OF COOPERATION IN HIGH SEAS FISHERIES: A CHARACTERISTIC FUNCTION GAME APPROACH

In the current paper we examine a game-theoretic setting in which three countries have established a regional organization for the conservation and management of straddling and highly migratory fish stocks. A characteristic function game approach is applied to describe the sharing of the surplus benefits from cooperation. We demonstrate that the nucleolus and the Shapley value give more of the benefits to the coalition with substantial bargaining power than does the Nash bargaining scheme. We also compare the results that are obtained by using the nucleolus and the Shapley value as solution concepts. The outcomes from these solution concepts depend on the relative efficiency of the most efficient coalition. Furthermore, the question of fair sharing of the benefits is considered in the context of straddling stocks.     

A MODEL OF CHINOOK SALMON POPULATION DYNAMICS INCORPORATING SIZE‐SELECTIVE EXPLOITATION AND INHERITANCE OF POLYGENIC CORRELATED TRAITS

Abstract Concern regarding the potential for selective fisheries to degrade desirable characteristics of exploited fish populations is growing worldwide. Although the occurrence of fishery‐induced evolution in a wild population has not been irrefutably documented, considerable theoretical and empirical evidence for that possibility exists. Environmental conditions influence survival and growth in many species and may mask comparatively subtle trends induced by selective exploitation, especially given the evolutionarily short time series of data available from many fisheries. Modeling may be the most efficient investigative tool under such conditions. Motivated by public concern that large‐mesh gillnet fisheries may be altering Chinook salmon in western Alaska, we constructed a stochastic model of the population dynamics of Chinook salmon. The model contained several individually based components and incorporated size‐selective exploitation, assortative mating, size‐dependent female fecundity, density‐dependent survival, and the heritability of size and age. Substantial reductions in mean size and age were observed under all scenarios. Concurrently reducing directional selection and increasing spawning abundance was most effective in stimulating population recovery. Use of this model has potential to improve our ability to investigate the consequences of selective exploitation and aid development of improved management strategies to more effectively sustain fish and fisheries into the future.     

自贸区贸易创造和贸易转移效应测度:以中国-东盟自贸区为例

将自贸区建立产生的贸易效应分解为贸易创造和贸易转移是FTA福利分析和效果评价的核心研究内容.首先从理论推导,实证研究思路和研究方法3个层面探讨了FTA贸易效应的分解思路;构建了单国模式条件下贸易效应的测算方法;基于农产品贸易视角测度了中国-东盟自贸区的贸易创造和贸易转移效应,对模型的适用性进行了评价.结果表明,笔者构建的模型能够获取稳定和一致的估计结果,较好地拟合实际贸易,可以将这一模型推广应用于其他FTA的事后研究.