Optimum reserve size,fishing induced change in carrying capacity,and phenotypic diversity

Fish stocks around the world are heavily overexploited in spite of fishing policies in several parts of the world designed to limit overfishing. Recent studies have found that the complexity of ecological systems and the diversity of species, as well as negative impact of fishing activities on environmental carrying capacity of fish stocks—all contribute to the problem. A number of biologists, managers, and practitioners strongly support the use of marine reserves as a management strategy for marine conservation. This paper contributes to this line of research by seeking an optimum reserve size and fishing effort for situations where species diversity decrease at fishing grounds and fishing activities impact carrying capacity. We found that a reserve size which maximizes economic rents could ruin a fish stock if fishing impacts are not accounted for. On the other hand, the reserve serves as a bifurcation term which could improve the resilience of a marine ecosystem.     

Economics of biodiversity and sustainable fisheries management

Marine ecosystems are complex, and many marine species are ecologically interdependent. As a result, losing a species could produce a cascading effect on other species. Fishery scientists advocate an ecosystem-based approach to fishery management to meet long-term sustainable goals. This paper models the complex interrelationships among species and the relationship between biomass growth and phenotypic diversity. We found that the equilibrium stock and catch/yield levels are overestimated when the diversity is not accounted for. Consequently, if species are diverse, fishery policy based on a single fishery management could overestimate catch potentials and potentially results in biological overfishing and stock collapse.     

Heterogeneous Response to Marine Reserve Formation: A Sorting Model approach

The bioeconomic impacts of spatial fisheries management hinge on how fishing vessels reallocate their effort over space. However, empirical studies face two challenges: heterogeneous behavioral responses and unobservable resource abundance. This paper addresses these two problems simultaneously by using an unusual data set and an estimation technique developed in the industrial organization literature. We apply the methods to location and species choices in the Gulf of Mexico reef-fish fishery. The models are used to explore spatial effort substitution in response to two marine reserves. Individual attributes from a survey of vessel captains are linked to each fisherman’s observed daily trip information to control for observable heterogeneity. Some unobservable abundance information is captured by location- and species-specific constants and estimated by contraction mapping. The empirical results confirm that there is significant heterogeneity in fishermen’s response to the formation of marine reserves. They also show that ignoring unobservable abundance information will lead to significant bias in predicting spatial fishing effort.     

Boundary conditions for the sustainable use of major fish stocks in the Baltic Sea

The history of the management of Baltic fishery resources suggests that both biological and non-biological factors influence management decisions and that both types of information are essential for management which promotes sustainability. There is a direct link between the exploitation level and the risks for fishing as an economic activity due to fluctuations in the resource. This paper analyses the sustainability of the present catch levels of major Baltic fish stocks. By examining the rate of fishing mortality and recruitment variability, the possibility of sustaining present catch levels can be investigated. Current catch levels of Baltic cod and some salmon stocks are not sustainable whereas sprat and herring catches are. High rates of fishing mortality of cod and salmon may endanger stocks if a drop in the recruitment causes an increase of the fishing mortality rates in order to sustain short-term catches. By analysing the trade off between exploitation level and risk of stock decline, managers can obtain a basis for quota negotiations.     

Implications of a Discard Ban in Multispecies Quota Fisheries

We present an analysis of quota regulation and discarding in multispecies fisheries, explicitly taking into account the costs of non-compliance with quotas and a possible discard ban, as well as the costs of selective fishing (avoidance effort). We examine the impact of a discard ban on vessels’ profit maximising behaviour, in particular where species quotas are not set in proportion to their availability on the fishing grounds, considering both non-tradeable quotas and ITQs. We show the interdependence between penalty rates for both discards and over-quota landings in determining quota market outcomes. We find that quota prices are sensitive to penalty rates and to the presence of restrictive quotas for “choke” species.     

Economic and conservation implications of a variable effort penalty system in effort-controlled fisheries

Bycatch of threatened, endangered or protected species by commercial fishers is a universal problem. Technical solutions are often applied that may impose inefficiencies across the fleet, even in periods or areas when the risk of bycatch is low. These may include gear specifically designed to avoid the bycatch which may also reduce the targeted catch, or designation of marine protected areas that exclude fishing from whole areas. In this article, we examine the effectiveness of a variable penalty system that can provide incentives for fishers to redirect their effort away from problem areas. The system is examined using a case study of fishery, which is currently subjected to gear and closure controls to limit bycatch of turtles and seabirds. An alternative incentive-based management policy using a series of differential hook penalties has been proposed as a flexible tool to discourage vessels operating in certain areas. The effects of various hook penalties and closures in key areas on fishing effort in those areas and elsewhere as well as vessel economic performance are assessed using a location choice model. The results suggest that incentive-based approaches may result in lower costs to industry than closures provided some level of residual bycatch is acceptable.     

Assessing the ecological and economic benefits of a no-take marine reserve

The management of marine resources is often impeded by a lack of models to integrate ecological and economic information on exploited populations. We used available biological and economic data for an overexploited population of the leopard grouper (Mycteroperca rosacea) to study if closing parts of the population to fishing would allow sustainable use and maximum economic benefits. Our results suggest that fishing should be closed in all spawning areas and in at least 50% of the adjacent areas. High non-consumptive benefits would be achieved with large closures because the abundance of the leopard groupers, which is an important attribute for SCUBA divers, would increase. In a no-take reserve, the welfare gains of divers seemingly could compensate for losses incurred by fishers if parts of their fishing grounds are closed. An adaptive management scheme could provide a way to incorporate newly available information into management decisions for the no-take reserve.     

Trade-offs between conservation and socio-economic objectives in managing a tropical marine ecosystem

Understanding the trade-off relationships between ecological, economic and social objectives is important in designing policies to manage or restore ecosystems. Using the northern South China Sea (NSCS) as a case study, we explore the trade-offs between conservation and socio-economic objectives in managing fisheries in tropical marine ecosystems. Using a numerical optimization routine and ecosystem modelling (Ecopath with Ecosim), the study shows that current management of the NSCS is sub-optimal both in terms of conservation and economic objectives. Therefore, improvement in both conservation status and economic benefits can be achieved by reducing fishing capacity. However, the implementation of conservation plans may be hindered by the reduced number of fisheries-related jobs and the lack of alternative livelihoods. Similar trade-offs are apparent in many tropical marine ecosystems. Thus, this paper supports claims from previous studies that solving the alternative livelihood problems appears to be a priority for improving management and conservation in these ecosystems. A buy-back scheme that is funded by fishers might be effective in reducing fishing capacity. However, public funds are required if management objectives focus strongly on conservation. This might be justified by the direct or indirect benefits to society that could be provided by well-conserved ecosystems. This study highlights the conflict between maximizing conservation and social objectives, although win-win solutions between conservation and economic objectives may be possible.     

Biological “hot spots” and their effect on optimal bioeconomic marine reserve formation

Biological “hot spots” are regions within a fishery that possess a larger growth potential than the surrounding areas. This paper analyzes how these biological hot spots influence the optimal bioeconomic marine reserve formation within a fishery. The presence of biological hot spots within a fishery creates an environment within which it is optimal to establish a marine reserve that increases the productivity and therefore the value of the fishery. This result is analyzed using heterogeneity in the intrinsic growth rates and carrying capacities within a fishery. Simulation results illustrate that the optimal reserve size in the presence of biological hot spots depends not only on the productive capacity of the reserve and the surrounding fishing grounds, but also on the degree of heterogeneity between the two regions.     

Fishing in a Shallow Lake: Exploring a Classic Fishery Model in a Habitat with Shallow Lake Dynamics

Renewable resources such as fish exist within habitats. Harvesting activities may directly impact the habitat, beyond the influence caused by changing the balance between species. When harvesting activities impact stock size and habitat health in different ways, both states must be explicitly considered. A classic fisheries model is embedded in a habitat that exhibits shallow lake dynamics, where carrying capacity depends on habitat health and fishing effort damages the habitat. Hysteresis in the habitat dynamics can manifest itself as multiple steady states for both the dynamic and open access solutions. Numerical explorations of the model suggest that a new fishery in such a setting should often be managed to protect the health of the habitat, while it may not be optimal to restore a fishery in an already degraded habitat. Conventional policy tools applied in their classic form are unlikely to be effective.     

A Bioeconomic Analysis of a Shellfishery: The Effects of Recruitment and Habitat in a Metapopulation Model

This paper presents a bioeconomic model wherefishing effort exerted has multiple impacts onthe recruitment process of a sedentaryshellfish population. Recognizing thatsedentary populations generally possessmetapopulation characteristics at therecruitment stage, we show that fishing effortexerted not only influences the recruitmentprocess indirectly by limiting the number ofadults that spawn, but also directly byaffecting the habitat in which shellfish larvaerecruit. Depending on the recruitmentcharacteristics, fishing can have negative andpositive direct and indirect effects on therecruitment process. Next, a positive directeffect that fishing can have on the growth rateof the shellfish population if space to recruitto is limited is studied. Generalcharacteristics of sustainable fishing areanalyzed for the case that recruitment occursimmediately once spawning has occurred as wellas for the case that recruitment takes placeover a longer period of time. Conditions areidentified under which shellfishing should beencouraged in order to facilitate therecruitment process of juveniles. The paperends by analyzing how fishing alters theoptimal sustainable solution when itcontributes to habitat destruction.     

Challenges for economic policy in sustainable management of marine natural resources

The sustainable management of marine natural resources presents particular challenges to the managers of those resources. While such management has typically been based on biological considerations, it is argued that this has resulted in overexploitation and destruction of important marine assets in industries such as fishing and tourism. Consequently, it is concluded that other approaches are needed, with the use of economic concepts and management tools particularly relevant. At the same time, the human welfare outcomes of the application of various policy instruments must be carefully considered. While biological information is critical to the formulation and implementation of successful management regimes, it is concluded that the application of economic instruments will become more attractive to resource managers, with these instruments underpinned by consideration of property rights and an appropriate allocation of economic rents. A greater focus on these economic matters will take resource managers further in the direction of sustainable management of increasingly scarce marine resources. The conclusions in the paper are supported by various case studies from fisheries and tourism.     

Cooperative and Non-Cooperative Exploitation of the Arcto-Norwegian Cod Stock

A two-agent model for the exploitation of the Arcto-Norwegian cod stock is developed to investigate the economic benefits that can be realized from the resource, and the effect of exploitation on stock sustainability under cooperation and non-cooperation. The two agents are identified in this study as a trawl fishery versus a coastal fishery. Unlike in Munro (1979), where conflicts in the management strategies of agents arise from differences in the perceptions of the discount factor, fishing effort costs, and consumer preferences, here conflicts arise mainly from the differences in fishing gear and grounds, and the age group of cod targeted by the two agents. Using a game theoretic framework, we show that given available data, the optimum optimorum is obtained under cooperation with side payments and no predetermined harvest shares, in which case the coastal fishery buys out the trawl fishery. However, sensitivity analysis shows that if the price premium assumed for mature cod is taken away, the trawl fishery takes over as the producer of the optimum optimorum.     

Ecological and economic sustainability in fishery management: A multi-agent model for understanding competition and cooperation

Recent studies have shown that many marine ecosystems are experiencing an accelerating loss of population and biodiversity. It is apparent that there is a growing disparity between the available supply of fish and the desire of the growing world population to catch them. Although studies have begun to question the ecological sustainability of managed fishery systems, they often omit the corresponding effects on the economic sustainability of fishery industries. This is particularly important in rural coastal areas where the fishing industry is often a dominant employer. In this article, we analyze the interactions between economic and ecological dynamic systems using a multi-agent dynamic model of fishery management. Multiple agents (fishers) harvest multiple fish species and adapt the amount and allocation of their effort to their value functions, which are given as net profits of the fish harvest sold for a market price. This is largely unique in fishery models, since many econometric studies view fishers as represented by homogenous ‘average’ agents. We introduce and compare two different decision rules governing the behavior of fishers engaged in a competitive market. We demonstrate a situation where both behaviors lead to a decline of all fish stocks, as well as profits for most fishers. As an alternative, we introduce a cooperative approach in which fisheries jointly set sustainable limits for total harvest and effort that are then distributed to the fishers according to distribution rules. The simulation reveals that fish stocks and profits can stabilize at significantly higher levels in the cooperative case, leading to a continuous accumulation of capital for all fishers. This model demonstrates key aspects of overfishing conflicts that can be overcome through planned fishing quotas and cooperative market mechanisms. It also demonstrates a novel approach for simulating the dynamic behavior of heterogeneous fishers.     

ENTRY AND IMPORT QUOTA

An import quota set stricter than the free trade level is quite common for the domestic entry protection. However, this paper shows that as the products are vertically differentiated, an import quota that is simply set at the original free trade level could be effective on entrant protection. This quota policy also improves both consumer surplus and total domestic welfare, which is in sharp contrast to the implications of existing literature. Our result suggests that an import quota has a stronger protection effect on domestic production if the domestic and foreign products are vertically differentiated.     

Costs and Benefits of Bycatch Reduction Devices in European Brown Shrimp Trawl Fisheries

Discarding of juvenile fish is a wellrecognised problem in shrimp fisheries. In manycases, these fish are commercial species that,if not caught, could increase the productivityof other fisheries. In January 2003, Europeanlegislation was implemented by Member Statesrequiring all vessels fishing for brown shrimpto use selective trawls in order to minimisethe bycatch of other commercial species. Incomplying with the regulations, however, thecatch rate of the target species (the shrimp)is likely to be reduced. In this paper, we usea bioeconomic model to assess the impact ofbycatch reduction devices on fishing effort,catch and profitability in the European Crangon fisheries. The potential benefits (interms of higher future yields and consequentlyhigher profits) to the white-fish fisheries arealso estimated. From the model results, theregulation is expected to result in a netreduction in the profitability of the shrimpfishers. However, the benefits to thewhite-fish fishers is expected to more thanoffset this cost, resulting in an overall netbenefit.     

Fishing Technology and Optimal Distribution of Harvest Rates

This paper examines the problem of the optimal management of a joint-ownership fishing exploitation, where agents use different fishing gears. We consider a model in which the fishing activity may affect resource growth, not only through the harvest function but also through the natural growth rate of the resource. This allows us to capture the fact that some fishing gears alter the natural growth rate of the resource. We find that when the natural growth of the resource is altered by the fishing technology, the optimal stock is not independent of how harvest quotas are distribute among the agents. As a result, a fishing policy that firstly determines the optimum stock and, secondly, decides how to distribute the harvest among the different agents, will not be efficient. We also analyze the joint determination of optimal stock and harvest quotas and show that positive harvest quotas will only be optimal when countries are characterized by certain asymmetries.     

Renegotiation–Proof Equilibria in a Global Emission Game When Players Are Impatient

In a two-country model, in which countries differ with respect to the perception of environmental damages and abatement costs, the stability of international environmental agreements is analyzed in a dynamic framework. Three types of agreements are considered: A socially optimal solution, a uniform emission tax (a tax equally applied in both countries) and a uniform emission reduction quota (an equal percentage emission reduction from a base year). Stability is checked for these agreements according to the concept of renegotiation-proofness. It is shown that the stability requirements depend crucially on the parameters defining the interests of the two countries and the type of agreement. Moreover, it is demonstrated that if punishment options are restricted for some reason the stability of an agreement may suffer. One important result of the paper is that if countries exhibit asymmetric interests, stability in the quota regime is higher than in the tax regime and in the social optimum. This might explain why emission reduction quotas have been so popular in international politics despite recommendations of economists to use market-based instruments.     

Enjoying Catch and Fishing Effort: The Effort Effect in Recreational Fisheries

Recreational fishermen derive utility from catch and fishing effort. Building our analysis on the Gordon-Clark model for renewable resources, we show that a lower importance of catch may result in higher catches. While this effect also holds under first-best management, it may destabilize open-access recreational fisheries to the point of stock collapse. Technical progress in recreational fisheries may mask such dynamics as it enables unaltered angler behavior and constant catches during stock declines.