A deterministic, forecasting, equilibrium study has been conducted of the multispecies and multi-métier fisheries of the Celtic Sea, ICES divisions VIIf and g. Calculations have been made of the optimal fleet sizes and mesh sizes required to maximize objectives of joint relative sustainable yields, gross revenue and net revenue. The species modelled are the resident populations of cod (Gadus morhua), whiting (Merlangius merlangus), sole (Solea solea), plaice (Pleuronectes platessa) and Norway lobster (Nephrops norvegicus), with additional consideration given to catches of hake (Merluccius merluccius), monkfish (Lophius sp.) and megrim (Lepidorhombus whiffiagonis). The fleet métiers modelled are the beam trawls, Nephrops otter trawls and non-Nephrops otter trawls. If mesh sizes can be calculated independently foreach métier, then the yields and the gross revenue are maximized by increased effort and mesh sizes, especially in the non-Nephrops fleet. If a common mesh size is required for all fleets, then the yields and the gross revenue are maximized when (i) this mesh size is of 114 mm, (ii) the fishing effort in beam and Nephrops fleets is significantly increased, (iii) the non-Nephrops fleet is almost eliminated. Maximization of net revenue requires a mesh size similar to the current mesh of 80 mm, but with significant reductions of fishing effort in all fleets. Average profitability is increased by 50 millions EUROs per year for the Celtic Sea fishery. The model provides a basic structure for examining the management with a more realistic dynamic and stochastic description of the Celtic Sea fisheries.

In 1983, the European Community (EC) agreed on a system for the conservation and management offishery resources which is based largely on the use of annual total allowable catch (TAC). Nevertheless, the state of many European stocks of demersal species has worsened since 1983. A review of TAC enforcement shows that landings have exceeded TACs to a limited extent for these resources. The contrary is observed for the stocks of pelagic species of which the state has improved although landings have frequently been larger than TACs. This double paradox generates a feeling of limited impact of the TAC system implemented by the EC. To investigate the reasons, the closeness between agreed TACs and scientific recommendations has been examined. The results show that the TAC decision process gives some preference to stability but attention is paid to the scientific recommendations. Finally, the lack of accuracy of predicted changes of fishing mortality in catch forecasts is found to have played a critical part in the failure of TACs to avoid the deteriorations of resources observed in EC waters. It leads to the conclusion that evaluation of risks in the TAC decision process and participation of actors of the fishing sector in risk management are important matters that cannot be avoided if one wants to improve the legitimacy of fisheries management and therefore its efficiency.

Management techniques in two sea scallop Placopecten magellanicus fisheries in Nova Scotia are compared and contrasted. In one, traditional management methods are used to protect the stock from overexploitation. In the other fishery, enterprise allocations in the form of quota shares are used to mimic property rights. Over the past decade, the fleets' reactions to stock conditions have been dramatically different. It is argued that the evidence supports a quasi-property management regime, though other factors are at play as well.

Fisheries management in the future will require that biological assessments be combined appropriately with operational, social, and economic considerations toward effective management of complex fisheries systems. This is not currently being done in fisheries management because of: (i) the lack of a conceptual and organizational framework for integrated and participatory decision making, and (ii) the lack of more appropriate methodologies for dealing with diverse sources of information, interdisciplinary objectives, and the inherent uncertainty of these systems. An integration of traditional "fisheries science" with other aspects of "fisheries management" and the field of "management science" in a new discipline of "Fisheries Management Science" is proposed. FMS is defined as "the rigorous application of the scientific method of problem solving in the development of strategic alternatives and their evaluation on the basis of objectives that integrate biological, economic, social, and operational factors into management decision making". Management science or operational research provides guidance in methodologies for complex decision making and problem resolution. A multidisciplinary decision framework is proposed involving the following key steps: (1) specification of quantifiable objectives and constraints; (2) modelling of the expected multicriteria performance of a range of proposed management decisions; (3) risk assessment through descriptions of the expected variability in performance measures; (4) risk management through analytical evaluation of risk and ranking of alternate solutions; and (5) continuous monitoring and improvement of past decisions including deviations from expected performance and corresponding adjustment of future alternatives toward achieving strategic objectives.

This paper examines the Canadian experience with quota managed fisheries, reviewing institutional structures and approaches. It begins with a review of management objectives following the extension of jurisdiction and traces the nature and rationale of changes. The specific measures used to achieve objectives are examined from a theoretical and practical perspective. The measures fall into two broad categories: conventional input controls: vessel and gear restrictions; and, output controls: tradable and non-tradable enterprise/individual quotas.

The experience indicates that input controls are largely ineffective in constraining effort. These measures fail to address the common property characteristics of the resource and consequently failed to blunt the incentives for share maximization and increased capitalization. These in turn lead to overfishing and misreporting, thereby undermining management objectives. Output controls in the form of individual tradable quotas fare better in constraining effort. They lead to fleet rationalization and improved quality and flow of raw material to processing facilities. But they may also lead to highgrading and discarding, as quantity incentives give way to unit-value incentives under the rights-based regime.

Some of the carly failures and more recent successes of policy are outlined, lessons are drawn and suggestions made about future directions.

Using the example of the New England Regional Fishenes Management Council and its attempts tu manage the fisheries in its area, this paper argues that disferences in the way Nature "operates" constitutes a major source of divisiveness between, on the one hand, those members (and other managers in, say, government) who use linear modeling systems and, on the other hand, the majority of those in the commercial fishing sector who, intuitively, have cast nature in those non-linear terms currently being explored in the Chaos paradigm. Since these two different models have not been explicitly addressed, there is a history of members on each side accusing those on the other of bargaining in poor faith and lacking an adequate understanding of the resource. The thesis of the paper is that making explicit these underlying cognitive modes would provide more "common ground" for addressing management problems in such co-management arenas as the fishery management councils and elsewhere.

Using examples, we discuss some aspects of surplus production models. Although the precision of some parameter estimators may appear to be good, the strong asymmetry of confidence intervals and the large impact of the choice of a given formula on those estimators go against this feeling. Models are often formulated with inference to the biological background, but giving a biological meaning to (the estimates of) the parameters may be very dangerous. Fishing effort standardization does not lead necessarily to useful results for management. The fleet dynamics, per se, may not allow equilibrium States. In the context, of general frameworks, where the evaluation of the resource is not the unique objective, surplus production models may be however very flexible tools for fishery analysis, with low parameter requirements.

This study concerns the dynamics and management of the hairtail fishery (Trichiurus haumela) in the East China Sea. Virtual population analysis was used to assess the historical pattern of stock size and an age-structured production model was developed to simulate the historical and future changes of catch and stock of hairtail under different fishing strategies. The results show that the stock of hairtail has been declining in general since the beginning of the 1960s. In 1981, it was 275.103 metric tons, overfished but not very seriously. Subsequent management measures brought some positive effects to stock and catches and slowed down the decline, but they cannot change the status of overfishing of the stock. The current fishing regime will inevitably lead to more severe depletion of the stock and also decrease the catch in the end. To prevent further deterioration of the stock and maintain catches, any further expansion of fishing effort must be stopped. Alternatively, a longer closed season should be introduced or the age at first capture should be raised.