AN INDICATOR FOR ECOSYSTEM EXTERNALITIES IN FISHING

Ecosystem externalities arise when one use of an ecosystem affects its other uses through the production functions of the ecosystem. We use simulations with a size‐spectrum ecosystem model to investigate the ecosystem externality created by fishing of multiple species. The model is based upon general ecological principles and is calibrated to the North Sea. Two fleets are considered: a “forage fish” fleet targeting species that mature at small sizes and a “large fish” fleet targeting large piscivorous species. Based on the marginal analysis of the present value of the rent, we develop a benefit indicator that explicitly divides the consequences of fishing into internal and external benefits. This analysis demonstrates that the forage fish fleet has a notable economic impact on the large fish fleet, but the reverse is not true. The impact can be either negative or positive, which entails that for optimal economic exploitation, the forage fishery has to be adjusted according to the large fish fishery. With the present large fish fishery in the North Sea, the two fisheries are well adjusted; however, the present combined exploitation level is too high to achieve optimal economic rents.     

MARINE PROTECTED AREA PERFORMANCE IN A MODEL OF THE FISHERY

ABSTRACT. What bio‐economic benefits can be expected from the implementation of marine protected areas (MPAs) in a fishery facing a shock in the form of recruitment failure, and managed jointly compared to separately? What are the optimal sizes of MPAs under cooperation and non‐cooperation? I explore these questions in the current paper by developing a computational two‐agent model, which incorporates MPAs using the North East Atlantic codfishery as an example. Results from the study indicate that MPAs can protect the discounted economic rent from the fishery if the habitat is likely to face a shock, andfishers have a high discount rate. The total standing biomass increases with increasing MPA size but only up to a point. Basedon the specifics of the model, the study also shows that the economically optimal size of MPA for cod varies between 50 70% depending on (i) the exchange rate between the protectedandunprotectedareas of the habitat; (ii) whether fishers behalf cooperatively or non‐cooperatively; and(iii) the severity of the shock that the ecosystem may face.     

INTEGRATING MARINE PROTECTED AREAS INTO MODELS FOR FISHERY ASSESSMENT AND MANAGEMENT

ABSTRACT. Marine protected areas (MPAs) have been proposed as an insurance policy against fishery management failures and as an integral part of an optimal management system for some fisheries. However, an incorrectly designed MPA can increase the risk of depletion of some species, and can reduce the value of the system of fisheries it impacts. MPAs may alter structural processes that relate fishery outcomes to management variables and thereby compromise the models that are used to guide decisions. New models and data gathering programs are needed to use MPAs effectively. This paper discusses the motivations and methods for incorporating explicitly spatial dynamics of both fish and fishermen into fishery models so that they can be used to assess spatial policies such as MPAs. Some important characteristics and capabilities which these models should have are outlined, and a topical review of some relevant modeling methodologies is provided.     

Regional economic impacts of fish resources utilization from the Barents Sea: Trade-offs between economic rent,employment and income

A multi-objective programming model has been developed to investigate the trade-offs among regional employment, regional income, and economic rent of the North Norwegian cod fisheries in the Barents Sea, where all vessels are regulated by an individual quota system. Fishery managers are confronted with the problem on how best to allocate the total allowable catch (TAC) among four vessel groups. It is apparent that depending on how fishery managers view the importance of each objective, the desirable allocation of TAC will differ. Therefore, the trade-offs information can be very useful to fishery managers indicating the relative “expensiveness” of trading one objective with another. Decision maps are generated depicting how the trade-offs between two objectives are affected by the third objective. Compromise solutions taking into account all three objectives will allocate the TAC to satisfy the maximum capacity of both the factory trawlers and the small-scale vessels with the remaining TAC distributed to the coastal fleet and fresh fish trawlers.     

Optimal harvesting of a Gompertz population model with a marine protected area and interval‐value biological parameters

To protect fishery populations on the verge of extinction and sustain the biodiversity of the marine ecosystem, marine protected areas (MPA) are established to provide a refuge for fishery resource. However, the influence of current harvesting policies on the MPA is still unclear, and precise information of the biological parameters has yet to be conducted. In this paper, we consider a bioeconomic Gompertz population model with interval‐value biological parameters in a 2‐patch environment: a free fishing zone (open‐access) and a protected zone (MPA) where fishing is strictly prohibited. First, the existence of the equilibrium is proved, and by virtue of Bendixson‐dulac Theorem, the global stability of the nontrivial steady state is obtained. Then, the optimal harvesting policy is established by using Pontryagin's maximum principle. Finally, the results are illustrated with the help of some numerical examples. Our results show that the current harvesting policy is advantageous to the protection efficiency of an MPA on local fish populations.     

THE INCOMPLETE‐INFORMATION SPLIT‐STREAM FISH WAR: EXAMINING THE IMPLICATIONS OF COMPETING RISKS

ABSTRACT. . It is now widely recognized that climactic regime shifts, which aperiodically alter a harvested fish stock's biomass and spatial distribution, may lead to distorted fisheries management decisions which negatively impact the fishery, both biologically and economically. This is particularly true for trans‐boundary migratory stocks, where optimal management relies on coordination among independent nation‐states. Unanticipated changes in stock distribution and abundance can upset expectations of national authorities, leading them to sanction inappropriate harvesting levels by their separately managed fleets targeting the same breeding fish stock. Our theoretical studies are based on a spatially‐distributed stochastic model, which we have called the “split‐stream model,‘ where two separately managed fleets harvest simultaneously at two separate sites. Our key assumption is that competing fleet managers, when harvesting noncooperatively, hold incomplete and asymmetric private information of current stock recruitment and spatial distribution. When subsequently negotiating to coordinate their harvests, they agree that they will share their information and then bargain over partition of the gains from their cooperation. This bargaining process takes into account the fleet's relative competitive strengths, particularly due to private information asymmetries. In this present article we introduce a more complex information structure than had been assumed in our earlier work (McKelvey and Golubtsov [2002], McKelvey, Miller and Golubtsov [2003], Mckelvey et al. [2004]). Specifically, both stock‐growth and stock‐split parameters vary stochastically and asynchronously. Thus, when harvesting noncooperatively, each fleet may possess private knowledge which is unavailable to the other. We examine the interplay of the harvesting game's information structure with other fishery characteristics, such as the fleets' economics and operating characteristics and their attitudes toward risk, to determine the implications of such structure for the outcome of the harvesting game. All of these changes are made to capture new conceptual phenomena and expand the range of applicability of the model.     

THE PROBLEM OF NONMALLEABLE CAPITAL REVISITED; A STUDY OF THE PACIFIC HALIBUT FISHERY

It has been suggested in the literature on commercial fisheries that fishing capital may be nonmalleable, i.e., not easily moved from one fleet to another, and that the socially optimal rate of capitalization of boats may depend on the degree of malleability (irreversibility) of the fishing fleet. To find out how irreversibility affects optimal regulation, two of the many possible regulatory tools, unallocated quotas and catch taxes, are examined. These optimal policies are derived, alternatively assuming malleable and nonmalleable fishing capital. Using a simulation of the Pacific halibut fishery, the results obtainable through catch quotas are shown to be inferior to those obtainable through taxes, but that the degree of malleability of capital has a surprisingly small impact on policy. A sensitivity analysis is performed, rerunning these simulations over a variety of parameter values. The previous results are largely borne out.     

A MODEL OF TROPICAL MARINE RESERVE‐FISHERY LINKAGES

ABSTRACT. The excessive and unsustainable exploitation of our marine resources has led to the promotion of marine reserves as a fisheries management tool. Marine reserves, areas in which fishing is restricted or prohibited, can offer opportunities for the recovery of exploited stock and fishery enhancement. In this paper we examine the contribution of fully protected tropical marine reserves to fishery enhancement by modeling marine reserve‐fishery linkages. The consequences of reserve establishment on the long‐run equilibrium fish biomass and fishery catch levels are evaluated. In contrast to earlier models this study highlights the roles of both adult (and juvenile) fish migration and larval dispersal between the reserve and fishing grounds by employing a spawner‐recruit model. Uniform larval dispersal, uniform larval retention and complete larval retention combined with zero, moderate and high fish migration scenarios are analyzed in turn. The numerical simulations are based on Mombasa Marine National Park, Kenya, a fully protected coral reef marine reserve comprising approximately 30% of former fishing grounds. Simulation results suggest that the establishment of a fully protected marine reserve will always lead to an increase in total fish biomass. If the fishery is moderately to heavily exploited, total fishery catch will be greater with the reserve in all scenarios of fish and larval movement. If the fishery faces low levels of exploitation, catches can be optimized without a reserve but with controlled fishing effort. With high fish migration from the reserve, catches are optimized with the reserve. The optimal area of the marine reserve depends on the exploitation rate in the neighboring fishing grounds. For example, if exploitation is maintained at 40%, the ‘optimal’ reserve size would be 10%. If the rate increases to 50%, then the reserve needs to be 30% of the management area in order to maximize catches. However, even in lower exploitation fisheries (below 40%), a small reserve (up to 20%) provides significantly higher gains in fish biomass than losses in catch. Marine reserves are a valuable fisheries management tool. To achieve maximum fishery benefits they should be complemented by fishing effort controls.     

PLANNING MARINE PROTECTED AREAS: A MULTIPLE USE GAME

Abstract The EU Marine Strategy Directive (MSD) has a regional focus in its implementation. The directive obliges countries to take multiple uses and the marine strategies of neighboring countries into account when formulating marine strategies and when designating marine protected areas (MPAs). We use game theoretical analysis both to find the optimal size of MPAs with multiple uses by multiple countries and to investigate the influences of multiple uses on cooperation. To this end, we develop a model in which two specific uses, fisheries and nature conservation, by multiple countries are considered in a strategic framework. The results of the paper suggest that EU marine policy such as the MSD and the coming Maritime Policy may help to secure the highest possible benefits from these MPAs if these policies induce cooperation among countries, but only if policies force countries to consider all possible benefits of MPAs. In fact cooperation on a single issue may give a worse outcome than the noncooperative equilibrium. The results also indicate that cooperation may be hard to achieve because of defector incentives, and therefore policy measures should be strict in enforcing cooperation on all possible uses of MPAs.     

FISHERIES AND MARINE PROTECTED AREAS: A SPATIAL BIOECONOMIC ANALYSIS OF DISTRIBUTIONAL IMPACTS

Abstract Marine protected areas (MPAs), used increasingly as a tool for conservation of ocean and coastal environments, typically interact with fisheries. Indeed, implementation of an MPA in a coastal region will likely affect fishing communities along that coast but to differing degrees depending on their location relative to the MPA. The resulting creation of “winners” and “losers” has implications for the acceptance and long‐term viability of the MPA. This paper develops a spatially explicit bioeconomic simulation model to assess the distributional implications resulting from creation of a no‐take MPA. The key assumption is that this results in certain fishers being displaced from the MPA to new fishing locations, leading to decreased fishing time and increased costs. Is it possible for those being displaced to end up as “winners” in the fishery? Analysis of the model indicates that such an outcome can occur in certain circumstances, notably if the biological effects of the MPA produce (i) improved ecosystem health inside the MPA, such that fish stock carrying capacity increases; or (ii) to some extent, high fish stock migration rates between neighboring areas. The results indicate that in creating MPAs, careful attention to their design is needed in order to deal with corresponding distributional impacts on fishing communities.     

OPTIONS FOR THE REGULATION OF MEDITERRANEAN DEMERSAL FISHERIES

Research and management actions are reviewed with respect to demersal fisheries of the Mediterranean since the Second World War, as reflected in the activities of the General Fisheries Council for the Mediterranean, (GFCM). The scientific background to the priority concern expressed for minimum size limits in the 1960's and 1970's is discussed, and in particular, the mesh selectivity experiments that formed the basis for yield per recruit calculations, with respect to the trawl fishery. More recent considerations, changing our perception of the appropriateness of size at first capture of demersal fish as a management tool in trawl fisheries, are reviewed. It is concluded that for multispecies fisheries where the first priority for fishing effort control is not respected, size limits based on size at maturity, rather than yield per recruit criteria, are more feasible, but that changes in mesh size need to take into account subsequent changes in equity between inshore and offshore fleets, and changes in species composition and areas of distribution during the life history. They also need to consider the high landed value of small fish in many Mediterranean fisheries. Alternative, or supplementary, measures to mesh size regulation that affect capture of small fish are also reviewed, including seasonal closures, closed areas, bans on trawling inshore, and regulations on minimum size at sale. A range of problems to be considered prior to deciding on an increase in mesh size are reviewed, including changes in total effort exerted, changes in increases in fishing power (and especially the impacts on the spawning stock), changes in discard rate, “meshing” of small fish, and indirect mortality during fishing. A strategy for introducing new mesh sizes is suggested, with emphasis, where possible, on the experimental approach, and on supplementary measures to control fishing effort. The paper concludes by considering an alternative paradigm to minimum size regulation for demersal fisheries management; namely, the exploitation of juvenile fish, with provision for escapement of a small proportion of large, mature fish offshore, for which exploitation rate declines and remains low. It is suggested that this strategy may be, de facto, the one prevailing in the small mesh size inshore trawl fishery prior to development of offshore fisheries. The implications of this possibility have to be considered seriously if high effort levels are to be maintained while effective size limits are raised.     

REBUILDING THE EASTERN BALTIC COD STOCK UNDER ENVIRONMENTAL CHANGE (PART II): TAKING INTO ACCOUNT THE COSTS OF A MARINE PROTECTED AREA

Abstract This study adds a cost analysis of the Eastern Baltic cod fishery to the existing model presented in Röckmann et al. [2007a] . As cost data on this international fishery do not exist, data from Denmark are extrapolated to the whole international fishery. Additionally, unit and total variable costs are simulated, and the sensitivity to a set of different cost–stock and cost–output elasticities is tested. The study supports preliminary conclusions that a temporary marine reserve policy, which focuses on protecting the Eastern Baltic cod spawning stock in the International Council for the Exploration of the Sea (ICES) subdivision 25, is a valuable fisheries management tool to (i) rebuild the overexploited Eastern Baltic cod stock and (ii) increase operating profits. The negative effects of climate change can be postponed for at least 20 years—depending on the assumed rate of future climate change. Including costs in the economic analysis does not change the ranking of management policies as proposed in the previous study where costs were neglected.     

A mixed integer programming model of a multicohort single-species fishery

Many marine fisheries are under pressure from overfishing. Fisheriesmanagement is a complex process because of the need to considerthe interaction of the biological components of the fishery,the technical characteristics of the fishing fleet, and theeconomic aspects of the fishing industry. In this paper, a mixedinteger programming (MIP) model for determining the policy tomaximize the long-run economic benefit from a single-speciesmulticohort fishery is developed. The model takes account ofthe biological, technical, and economic characteristics of thefishery, using integer variables to model the fishing activities.An iterative procedure for solving the model using commercialMIP software is described, and the viability of this procedureis illustrated using data for the western mackerel fishery.     

DEA-based predictors for estimating fleet size changes when modelling the introduction of rights-based management

The introduction of individual transferable quotas (ITQs) into a fishery is going to change not only the amount of catch a fleet can take, but often also changes the fleet structure, particularly if total allowable catches are decreased. This can have an impact on the economic, social and environmental outcomes of fisheries management. Management Strategy Evaluation (MSE) modelling approaches are recognised as the most appropriate method for assessing impacts of management, but these require information as to how fleets may change under different management systems. In this study, we test the applicability of data envelopment analysis (DEA) based performance measures as predictors of how a fishing fleet might change under the introduction of ITQs and also at different levels of quota. In particular, we test the assumption that technical efficiency and capacity utilisation are suitable predictors of which boats are likely to exit the fishery. We also consider scale efficiency as an alternative predictor. We apply the analysis to the Torres Strait tropical rock lobster fishery that is transitioning to an ITQ-based management system for one sector of the fishery. The results indicate that capacity utilisation, technical efficiency and scale efficiency are reasonable indicators of who may remain in the fishery post ITQs. We find that the use of these measures to estimate the impacts of lower quota levels provides consistent fleet size estimates at the aggregate level, but which individual vessels are predicted to exit is dependent on the measure used.     

BIOECONOMIC INTERACTIONS IN AN ESTABLISHED FISHING EXCLUSION ZONE: THE GULF OF CASTELLAMMARE,NW SICILY

ABSTRACT. Fishing exclusion zones have become a key management tool for habitat protection and species conservation within fisheries. In many instances, where overfishing or habitat destruction is taking place, they are being promoted strongly. For fisheries management, their use is widespread and their popularity growing. It is clear that in some cases marine protected areas may be crucial to sustaining resources. Most research to date has considered the biological or ecological effects of such reserves. However, little real analysis has been published that takes into account the links between the biology and the economics of the fisheries involved, making the economic benefits to fisheries less clear. This paper considers an exclusion zone which was implemented in 1990 in the Gulf of Castellammare, Sicily in the form of a trawl ban, modeling the potential effects of future policy in this area. The success of the trawl ban has far exceeded expectations, and it is simulated that it may be advantageous, under strict conditions, to relax the ban in part for some of the year.     

IS FISHING COMPATIBLE WITH ENVIRONMENTAL CONSERVATION: A STOCHASTIC MODEL WITH AN ELEMENT OF SELF‐PROTECTION

Abstract The purpose of this paper is to introduce the impact of fishing activity on a marine ecosystem. The fishing activity is considered not only through annual harvest but also through a second component, called the degree of protection of the fishery environment. This characterizes the environmental impact of fishing. A stochastic dynamic programming problem is presented in infinite horizon, where a sole owner seeks to maximize a discounted expected profit. The main hypothesis states that the stock–recruitment relationship is stochastic and that both components of the fishing activity have an impact on the probability law of the state of the fishery environment. The optimal fishing policy is obtained and compared with standard models. This optimal policy has the following properties: is not a constant escapement policy and indicates an element of self‐protection by the fishery manager. The paper ends with a discussion on the existence of degrees of protection of the fishery environment that take into account the environmental conservation and preservation of economic activity.     

EFFORT SUBSIDIES AND ENTRY DETERRENCE IN TRANSBOUNDARY FISHERIES

ABSTRACT. This paper analyzes a two-stage game, based on the Gordon-Schaefer model of the fishery, to examine the strategic entry-deterring role for effort subsidies in noncooper-ative transboundary fisheries. The game reveals that a country, whose domestic fleet has an effort cost advantage over a rival foreign fleet, may choose to subsidize domestic effort to the point that foreign entry in the fishery becomes unprofitable. Whether the outcome of the game is characterized by foreign entry deterrence or accommodation, and whether it is also characterized by a domestic effort subsidy or a tax, depends on domestic and foreign effort costs and the number of firms in each fleet. The various outcomes of the game analyzed here help to explain the persistence of subsidies in some world fisheries.     

OUTPUT VERSUS INPUT CONTROLS UNDER UNCERTAINTY: THE CASE OF A FISHERY

Abstract The paper compares the management outcomes with a total allowable catch (TAC) and a total allowable effort (TAE) in a fishery under uncertainty. Using a dynamic programming model with multiple uncertainties and estimated growth, harvest, and effort functions from one of the world's largest fisheries, the relative economic and biological benefits of a TAC and TAE are compared and contrasted in a stochastic environment. This approach provides a decision and modeling framework to compare instruments and achieve desired management goals. A key finding is that neither instrument is always preferred in a world of uncertainty and that regulator's risk aversion and weighting in terms of expected net profits and biomass, and the trade‐offs in terms of expected values and variance determine instrument choice.     

THE ECONOMICS OF CONFLICTING INTERESTS: NORTHERN BALTIC SALMON FISHERY ADAPTION TO GRAY SEAL ABUNDANCE

The successful conservation of gray seals has led to increased seal‐induced damage to the Atlantic salmon fisheries of the Baltic Sea. This paper addresses the conflict between the conservation of a formerly endangered species, the gray seal, and professional fishermen, whose livelihoods are affected by both seal‐induced damage and salmon fisheries management. We develop a bioeconomic model that incorporates the age structure of Atlantic salmon and gray seal populations. To determine the social optimum, we maximize the discounted net present value of the trap net fishery, taking into account the presence of seals in the form of seal‐induced losses, which we describe using a damage function. By choosing the optimal combination of fishing gear over time, we obtain the socially optimal fishing efforts, salmon stock size, and salmon catch. In addition, we study the private effects of introducing a technology subsidy aimed at mitigating the seal‐salmon conflict. The results suggest that technological adaptation would effectively reduce the cause of the conflict, while a technology subsidy encouraging such adaptation would shift the economic responsibility from individual fishermen to the broader public.     

Influence of prey reserve in a prey–predator fishery

The excessive and unsustainable exploitation of marine resources has to led to the promotion of marine reserve as a fisheries management tool. In this paper we study a prey–predator system in a two-patch environment: one accessible to both prey and predators (patch 1) and the other one being a refuge for the prey (patch 2). The prey refuge (patch 2) constitutes a reserve zone of prey and fishing is not permitted, while the unreserved zone area is an open-access fishery zone. The existence of possible steady states, along with their local and global stability, is discussed. We then examine the possibilities of the existence of bionomic equilibrium. An optimal harvesting policy is given using Pontryagin’s maximum principle.