Optimal Harvest in an Age Structured Model with Different Fishing Selectivity

An age structured model of a fishery is studied where two fishing fleets, or fishing agents, are targeting two different mature age classes of the fish stock. The agents are using different fishing gear with different fishing selectivity. The model includes young and old mature fish that can be harvested, in addition to an age class of immature fish. The paper describes the optimal harvesting policy under different assumptions on the objectives of the social planner and on fishing selectivity. First, biomass yield is maximized under perfect fishing selectivity, second, equilibrium profit (rent) is maximized under perfect fishing selectivity, and third, equilibrium profit is maximized under imperfect fishing selectivity. The paper provides results that differ significantly from the standard lumped parameter (also surplus production, or biomass) model.     

Measuring potential profits in a bioeconomic model of the mixed demersal fishery in the North Sea

This paper measures for potential profit in the North Sea mixed demersal fishery for cod, haddock and whiting. Dynamic bioeconomic models for three UK fisheries are developed, incorporating both population dynamics and economic structure. Actual profit in 2006, for the three UK fleets included in the analysis, is estimated at ??10.3?million. If the TAC remains unchanged but vessels are allowed to harvest at near efficient levels with fleet size reduced accordingly, potential profit is measured at ??34.5?million. If demersal stocks are allowed to recover to near optimal levels potential UK profit exceeds ??185?million. This indicates substantial profit dissipation due to overcapacity and stock depletion in the fishery. The results of the paper should be of policy interest and will add to the empirical literature on resource profits in mixed demersal fisheries.     

ITQ Systems in Multifleet Fisheries

Optimum management of a particular fishery is analyzed based on an ITQ system. For this purpose, a multifleet deterministic bioeconomic model is developed and applied. Using data on the fishery studied here, estimates are made of the stock dynamics of fish and the technology used by the fleets operating in said fishery. Optimum levels of stock, effort and catch are determined. Finally, we present economic policy recommendations for this fishery and considerations for applying regulatory measures.     

Cooperative and non-cooperative management of the Northeast Atlantic cod fishery

The fishery for Northeast Atlantic cod (Gadus morhua) in the Barents Sea is one of the most valuable fisheries in the North Atlantic. After the introduction of Extended Fisheries Jurisdiction, cod is a shared stock between Norway and Russia. Overfishing of quotas has been a concern for a number of years. The purpose of this article is to analyse cooperative and non-cooperative management of the Northeast Atlantic cod fishery. This will be done in a game theoretic context, based on different assumptions regarding important variables such as cost of effort and initial stock size. The game theoretic analysis will be based on an empirical bioeconomic model developed and estimated by Hannesson (Mar Policy 31:698–705, 2007; J Bioecon forthcoming). The case of cooperative management is analysed for different cost parameters and starting values of the stock. An interesting result is that the optimal policy gives rise to pulse fishing. As this involves effort (and harvests) varying from year to year, potentially imposing substantial social costs on the industry in years when the fishery is closed, a policy of constant effort is also considered. Finally, non-cooperative management is analysed.     

International Management Strategies for a Straddling Fish Stock: A Bio-Economic Simulation Model of the Norwegian Spring-Spawning Herring Fishery

In this paper, a three-country dynamic bio-economic simulation model is presented for the spring-spawning herring fishery. The international spring-spawning herring fishery, based on potentially one of the most valuable fish stocks in the world, is currently recovering from a severe depletion of the stock and subsequent harvesting moratorium. Management of the herring fishery is complicated by its multi-nation exploitation, due to the highly migratory behaviour of the species moving between several coastal state zones (exclusive economic zones, EEZs) and the high seas (Ocean Loop). Based on extensive work invested on analysing both the biology of the herring stock and the fisheries economics around its exploitation we study here the profiles of different multi-agent management schemes, simulating catch levels, stock size and profit potentials of alternative management strategies. The stock dynamics are described by a linear discrete-time age-structured population model and the economics are presented by a rent maximising model with constant price of herring catch and different costs of harvesting and efficiency levels for the different national fleets. The simulations, carried out over several decades, show that the benefits of international co-operation far exceed the returns of a competitive open access fishery.JEL Classifications: C7, C15, Q22     

Portfolio Fishing

The optimal fishing pattern in a multi-cohort fishery is determined using risk theory.Portfolio theory becomes applicable by treating different age groups of fish as different assets. A possibility set is derived using data on Icelandic cod fisheries. In the presence of risk aversion, it is shown that the abrupt behavior found in deterministic models is changed towards a smoother fishing pattern. The historical selection pattern for the Icelandic cod stock is shown to be near optimal using a maximal effort-type cost function, but historical levels of effort are inefficient and lead to less profit and greater fluctuations than implied by profit or utility maximization.     

Optimal fishery harvesting rules under uncertainty

This paper derives the optimal fishery harvest policy in a real-option model with a stochastic logistic growth process, harvest-sensitive output price, and both fixed and variable harvesting costs. The policy specifies the harvest trigger and harvest size, while outputs from the model include the value of the fishery and the risk of extinction. The optimal policy is illustrated with data from the Pacific Halibut Fishery. For this particular case, the optimal policy recommends harvesting when the fish stock rises to about three-quarters the environmental carrying capacity, and the amount harvested should be approximately a quarter of the prevailing stock. This harvesting policy maximizes the value of the fishery, and importantly, the resulting risk of extinction is negligible. We also carry out some sensitivity analysis to see how the optimal policy (and the resulting fishery value and risk of extinction) change when the input parameters are varied, particularly the ecological parameters intrinsic growth rate and volatility of the stock, and also the economic parameters that have been ignored in previous papers (price sensitivity and fixed cost). If the optimal policy is followed, the risk of extinction will be negligible, except for very low growth rate and high volatility.     

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.     

Transferable quotas,enforcement costs and typical firms: An empirical application to the Norwegian trawler fleet

An alternative to traditional regulations of fisheries to avoid rent dissipation is the use of individual transferable quotas (ITQ _s ) where prices in the quota market provide the necessary information to owners of harvest rights to contract with each other. However, even under such a decentralized regime, information on the underlying technology of the fishing vessels is also necessary. First, since most fisheries consist of many interrelated production processes, in order to avoid rent dissipation by discarding wrong output mix etc., the structure of production in the multispecies fishery must be known to design a proper quota system. Second, an ITQ system may create incentives for misreporting by understating the actual catch. This may especially be the case where the expected degree of self-enforcement is low. The paper proposes a way to reduce the information requirements under regulation with asymmetric information by constructing a typical firm and comparing performance for the other vessels to this firm. Based on the typical firm, and if the industry is relatively homogenous, the performance and hence catch of any other firm in the industry can be predicted within a certain range. Further, the paper applies this idea to the Norwegian trawler fleet to assess the production structure in terms of jointness, input-output separability, and the supply and demand elasticities for the fishing firms. This information characterizes the fishery and thus how the quota system may be designed and how to construct a yardstick in order to reduce the enforcement cost under a decentralized regulation of ITQs.The authors would like to thank Trond Bjørndal, Røgnvaldur Hannesson, Ola Flaaten and two referees for useful comments and suggestions.     

Restricted capacity and rent dissipation in a regulated open access fishery

A common strategy for limiting the total annual catch in a fishery is to restrict entry and season length. We examine the results of this strategy when entry limitation amounts to a limit on capital, but fishing firms can vary an unrestricted input, and thereby use the restricted input more intensively. Under these regulatory constraints, fishing firms will earn rents that depend on the elasticity of substitution between restricted and unrestricted inputs. Using simulations with data from the Alaskan pollock fishery, rents and season length are shown to depend on fish and variable input prices, sometimes in surprisingly non-monotonic ways.     

Coastal state fishery development: Foreign fleets and optimal investment dynamics

An economic optimization model is formulated to evaluate coastal state fishery development options, involving (i) the optimal level investment in the domestic fleet, (ii) the nature and extent of involvement by foreign ‘distant water’ fleets. The coastal state utilizes two regulatory tools: allocation of the annual Total Allowable Catch between domestic and foreign fleets, and imposition of a royalty on the foreign fleet's harvest. Depending on the royalty rate and specific combinations of economic parameters, the optimal pattern of fishery development may involve: exclusion from the fishery of one or the other of the fleets, transitory coexistence as one fleet depreciates over time, or stable long-term coexistence of both fleets. The initial fleet sizes, the unit cost of capital and the depreciation rate are found to play major roles in determining the extent of each fleet's participation in optimal exploitation of the coastal resource.     

Distributing the Benefits from the Commons: A Square-Root Formula

What should be the distribution of the benefits of a fishery (or common-pool resource) where a group of fishers catch fish and sell it to consumers? I propose that, for each person i, where i is a fisher or a consumer, i's returns should be proportional to i's contributions. Unexpectedly, this implies that the fraction of benefits accruing to consumers must be √value of total output of fish/√value of total outputs of fish+√value of total fishers' labor.     

Testing theoretical explanations for investment behaviour in the Dutch beam trawler fishery in the North Sea

In this study, we investigate whether the neoclassical economic theory, capital market frictions or preference-based theory can explain investment behaviour in the Dutch beam trawler fishery in the North Sea. By presenting a number of estimations, we show that vessels conducting pulse fishing invest substantially more than similar vessels undertaking conventional fishing, even after controlling for differences in such variables as capital stock, prices, profits and quotas. One possible explanation for this result is that vessel owners may obtain a separate benefit from investing in pulse fishing.     

The effects of El Niño on the mackerel purse-seine fishery harvests in Taiwan: An analysis integrating the barometric readings and sea surface temperature

The harvest of mackerel purse-seine fishery in Taiwan fell sharply by 47.75% following the strong El Niño of 1997/1998. In this study, we try to incorporate El Niño barometric readings and sea surface temperature measurements into analysis for predicting the biomass. Using daily logbook records of the mackerel purse-seine fishery from 1982 to 1999, we identify the factors that influence the catch of mackerel purse-seine fishery in Taiwan. Based on an empirical model and the results of a fishing fleet cost survey, we estimate the average cost and the welfare loss associated with an El Niño. A time-series simulation shows that adding the El Niño barometric readings information improves the accuracy of biomass forecasts. It also shows that about 14 months after the strong El Niño has occurred, the biomass index is 13.2% lower and the number of fishing day is 10.4% higher. The estimated welfare loss of all mackerel purse-seine fleets during September to January in the year subsequent to the El Niño is about US$6 million. Policy implications of the study are also discussed.     

Optimal Harvesting of an Age-Structured Schooling Fishery

Biologists have criticized traditional biomass models in fishery economics for being oversimplified. Biological stock assessment models are more sophisticated with regard to biological content, but rarely account for economic objectives. This study includes a full age-structured population model for studying schooling fisheries and extends the delayed difference approach used in earlier studies. We take the total harvest as the choice variable, resulting in a simple analytical structure. The model produces optimal steady states that may be higher or lower compared to the delayed-difference formulation. The model is applied to the Baltic sprat fishery. Both ecological and harvesting cost data support specifying Baltic sprat as a schooling fishery. Given nonlinear harvesting costs, the optimal solution is a path toward a steady state with smooth annual harvest and population age structure. Sensitivity analysis shows that the optimal solution is highly dependent on the population level of the sprat’s main predator Baltic cod. A linear cost function and an interest rate below 9 % imply pulse fishing instead of smooth continuous harvesting. Given nonlinear harvesting cost, the optimal steady state yield is rather insensitive to changes in the interest rate. However, under a high cod scenario, interest rates of 10 % or higher implies that no optimal steady state exists.     

Fishing Revenue, Productivity and Product Choice in the Alaskan Pollock Fishery

A key element in evaluating fishery management strategies is examining their effects on the economic performance of fishery participants, yet nearly all empirical studies of fisheries focus exclusively on the amount of fish harvested. The economic benefits derived from fish stocks involve the amount of revenue generated from fish processing, which is linked to both the way fish are harvested and the products produced from the fish. In this study we econometrically estimate a flexible revenue function for catcher-processor vessels operating in the Alaskan pollock fishery, recognizing potential endogeneity and a variety of fishing inputs and conditions. We find significant own-price supply responses and product substitutability, and enhanced revenues from increased fishing days and tow duration after a regulatory change introduced property rights through a new fishing cooperative. We also find significant growth in economic productivity, or higher revenues over time after controlling for observed productive factors and price changes, which exceeds that attributable to increased harvest. These patterns suggest that the move to rights-based management has contributed significantly to economic performance in the pollock fishery.     

Spare the Young Fish: Optimal Harvesting Policies for North-East Arctic Cod

The North-East Arctic cod (Gadus morhua) fishery, as most other commercial fisheries, is wasting the larger part of its potential. Examining a detailed multi-cohort, multi-gear bioeconomic model, we show that the cause is rather a too small mesh size than excessive effort. Although internationally and nationally managed by quota allocations and regulations, the current exploitation pattern implies that essentially the wrong fish are targeted. Catching older and heavier fish could double the fishery’s Net-Present-Value. This increases harvested biomass while it reduces the number of fish removed from the ocean, highlighting the importance of age- and gear-specific modeling. Moreover, optimal harvesting policies would also lead to a much more robust and abundant cod stock.     

Individual Rationality and the “Zonal Attachment” Principle: Three Stock Migration Models

Shared fish stocks migrate across borders between different countries’ exclusive economic zones. This paper discusses the individual rationality of fish-sharing agreements based on the zonal attachment of such stocks. Three types of migrations are considered: (i) a common stock that grows and reproduces and is then distributed in given proportions between two countries’ zones at the beginning of each fishing season; (ii) sub-stocks that breed and grow independently in their separate zones but spill over between zones according to relative abundance; (iii) a stock that grows and breeds in one country’s zone but migrates into the zone of another if it exceeds a certain size. It is shown that in all these cases the minor partner in a fish-sharing agreement may not have an incentive to cooperate unless he gets a larger share of the cooperative profits than that corresponds to his share of the stock. This is particularly likely to happen when the unit cost of fish does not depend on the stock. An exception could occur if stock migration depends on the stock level; the major partner could then keep the entire stock by fishing it down to a critical level.     

Endogenous Fishery Management in a Stochastic Model: Why Do Fishery Agencies Use TACs Along with Fishing Periods?

This paper seeks to explain the circumstances under which using total allowable catch (TAC) as an instrument to manage a fishery along with fishing periods may be of interest from a regulatory point of view. The deterministic analysis by Homans and Wilen (J Environ Econ Manag 32:1?C21, 1997) and Anderson (Ann Oper Res 94:231?C257, 2000) is thus extended to a stochastic scenario where the resource cannot be measured accurately. The resulting model is solved numerically to find the optimal control rules in the Iberian sardine stock. Three relevant conclusions can be highlighted from simulations: first, the greater the uncertainty regarding the state of the stock, the lower the probability of the fishery being closed before the end of the fishing period. Second, the use of TACs as a management instrument in fisheries that are already regulated by fishing periods leads to: (i) an increase in the optimal season length and harvests, especially for medium and high numbers of licences; (ii) improved biological and economic variables when the fleet is large; and (iii) extinction risk for the resource being eliminated. Third, the regulator would rather select the number of licences than restrict the season length.     

A Stackelberg Game Model of Trade in Renewable Resources with Competitive Sellers*

We model international trade in renewable resources between a single buyer and competitive sellers as a Stackelberg differential game. The buyer uses unit and ad valorem tariffs to indirectly encourage conservation of the renewable resource under study. First, we show that the efficacy of these trade policy instruments in promoting conservation depends fundamentally on whether harvesting costs are stock dependent or independent. When harvesting costs are stock independent, the optimal open‐loop tariffs are dynamically consistent. In contrast, when harvesting costs are stock dependent, the optimal open‐loop tariffs are dynamically inconsistent. Secondly, we point out that whether the terminal value of the resource stock is higher with the stock independent or the stock dependent cost function cannot be resolved unambiguously. Thirdly, we show that it does not make sense for the buyer to use both tariffs simultaneously. Finally, we discuss the implications of these and other findings for renewable resource conservation in general.