Optimal Intra- and Interseasonal Harvesting Strategies when Price Varies with Individual Size

A major concept in fisheries management is the optimal age for first capture. Because there can be separate market categories for fish of different sizes and different costs for their harvest, a more rational statement of the problem would be to find the optimal range of harvest sizes in any given year. Two models for solving this problem are presented. The shrimp model discusses optimal harvest of a single cohort of shrimp as it grows through a season. The lobster model discusses optimal simultaneous harvest of several cohorts over several seasons. The difficulty of defining a cost per fish in the lobster model makes it a much more complex undertaking.Optimal harvesting, intraseason, interseason, variable price, fisheries management, Demand and Price Analysis, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Cyclical and constant strategies in renewable resources extraction

This paper is concerned with the classic topic of intertemporal resource economics: the optimal harvesting of renewable natural resources over time by one and several resource owners with conflicting interests. The traditional management model, dating back to Plourde (1970), is extended towards a two–state model in which harvesting equipment is treated as a stock variable. As a consequence of this extension, an equilibrium dynamics with bifurcations and limit cycles occur. Next we discuss conflicts as a game with two types of players involved: the traditional fishermen armed with the basic equipment and the heavy equipment users. Both players have a common depletion function, thought as harvesting, which is dependent both on personal effort and on intensity of equipment’s usage.Renewable resources; exploitation of natural resources; differential games

NATURAL RESOURCE ACCOUNTING AND SOUTH AFRICAN FISHERIES: A BIO-ECONOMIC ASSESSMENT OF THE WEST COAST DEEP-SEA HAKE FISHERY WITH REFERENCE TO THE OPTIMAL UTILISATION AND MANAGEMENT OF THE RESOURCE

Resource /Energy Economics and Policy,

Stochastic Bioeconomics: A Review of Basic Methods and Results

Basic bioeconomic models which incorporate uncertainty are reviewed to show and compare the principal methods used and results reported in the literature. Beginning with a simple linear control model of stock uncertainty, we proceed to discuss more complex models which explicitly recognize risk preferences, firm and industry behavior, and market price effects. The effects of uncertainty on the results of bioeconomic analysis are rarely unambiguous, and in some instances differ little from corresponding deterministic results. This review is presented to enhance readers' appreciation of the papers to follow in this and the next issue of the journal.Environmental Economics and Policy, International Development, Resource /Energy Economics and Policy, Risk and Uncertainty,

COMMENT: MARINE RESERVES: WILL THEY ACCOMPLISH MORE WITH MANAGEMENT COSTS?

Hannesson (Marine Resource Economics 13(3) 1998) takes a critical approach to marine protected areas (MPAs) using simulations of MPAs combined with open access. His results show the conservation effect of an MPA of an appropriate size being the same as that achieved with optimal quota regulation, but with a smaller catch. We expand this analysis by adding a management cost function and increasing the fishing costs to a more realistic level. It is shown that the use of MPAs of certain sizes can be a more advantageous management tool than traditional quotas; hence, the inclusion of management costs modifies some of the findings of Hannesson (1998). We also illustrate how sensitive the results are to the choice of fishing cost values, making the attractiveness of private property versus marine reserves much less clear than proposed by Hannesson (1998).Resource /Energy Economics and Policy,

Strategic Review of Tropical Fisheries Management

This project addresses the constraints to tropical fisheries development with sustainable exploitation through a strategic assessment of tropical fisheries management with the following purposes: (1) To evaluate relevant research methods for the development of assessment models appropriate to the circumstances of tropical coastal fisheries; and (2) To evaluate the utility of existing strategies for the implementation of management advice. The report consists of three substantive chapters. Chapter 2 contains a detailed socio-economic assessment of various instruments and implementation strategies applicable to tropical capture fisheries. In Chapter 3, a detailed assessment of the fisheries for tropical large marine ecosystems has been conducted using a technique developed by FAO (Granger & Garcia 1996). The data used were the FAO statistics published regularly by FAO. This analysis has been conducted for each of the tropical large marine ecosystems and indicates that there is the potential for increased fishing in a number of these ecosystems. One of the clear requirements identified in Chapter 2 and implicit in Chapter 3, is that there is a significant need for simple and robust fisheries assessment methods which can estimate the potential of a particular resource, its capacity in terms of the level of fishing effort and its current status ie whether it is currently exploited sustainably or not. In Chapter 4, these problems are addressed directly and, using two approaches, significant simplification of fishery methods is developed. In the first approach, simple empirical relationships between the life history parameters of a species are used to develop models of potential yield which can be determined by a simple assessment of fish growth. In the second approach, optimal life history theory is applied to the key demographic parameters of exploited fish populations and using estimates of the Beverton & Holt invariants a significant simplifying of the basic stock assessment equations is developed

Lake Victoria Fisheries Management Plan

The purpose of this Fisheries Management Plan (FMP) within the Lake Victoria Fisheries Research Project was to sustain the livelihoods of the communities who depend on the fishery resources of the lake and to reduce poverty, food insecurity and unemployment. To achieve this goals, a better management of the resources, which would mobilize and include stakeholders at local, regional, national and international level was believed to be the right strategy for success. (PDF contains 79 pages