Practical issues in choosing a framework for resource assessment and management of Mediterranean and Black Sea fisheries

Local context and practical constraints are important in deciding on assessment procedures for Mediterranean and Black Sea fisheries, and in formulating management measures that reflect the resource life history, fishery configuration and availability of data. A brief review of existing methods is provided, and a recommendation that practical approaches need to focus on developing the indicators and reference points appropriate for fisheries management decisions. In both the Black Sea and Mediterranean Sea proper, experience suggests environmental and ecosystem concerns must be given a high priority in the assessment process

Analysis of seasonal growth through the application of a multiple linear regression model on data from tag-and-recapture experiments

When the Brody coefficient K is subject to temporal variation, data from tag-and-recapture experiments permit analysis of seasonal growth. Temporal values for K can be estimated without using a pre-determined oscillating function and the impact of seasonality on annual growth can be analyzed more realistically. The method is applicable to intra-annual intervals of single or multiple cohorts

Fisheries thematic mapping : a prerequisite for intelligent management and development of fisheries

Le document discute la pertinence de la cartographie thématique dans le contexte général de l'halieutique et indique l'importance de la cartographie des ressources, en particulier dans les ZEE des pays en développement. La perspective historique du développement de la science halieutique dans les zones de pêches traditionnelles confirme que la cartographie des ressources est une première et importante étape de l'évaluation des stocks, particulièrement dans la zone côtière. Certaines méthodes d'évaluation découlant directement de cette cartographie sont mentionnées, ainsi que les dangers d'une utilisation abusive de modèles supposant que les hypothèses d'homogénéité s'appliquent à des populations géographiquement grégaires et sous-dispersées. Le document passe en revue les diverses considérations spatiales qui affectent les divers types d'analyses effectuées sur les pêcheries. On y propose quelques critères et une classification grossière des divers types d'application de la cartographie aux pêches, y compris leur utilisation pour la pêche exploratoire, les prospections des navires de recherche, les systèmes de collecte des statistiques, la préparation des plans d'aménagement, l'allocation de l'espace maritime pour l'aquaculture, l'aménagement du littoral et les études d'impact, les négociations concernant les frontières maritimes et les accords de pêche. La périodicité de la mise à jour des cartes varie selon les applications. Dans certains cas, le principal souci doit être la facilité de mise à jour plutôt qu'une grande précision dont la nécessité est souvent limitée par les capacités de positionnement des petits bateaux de pêche. Le document insiste, enfin, sur la nécessité de promouvoir l'application en routine de technologies telles que les microordinateurs et la télédétection, ainsi que l'élaboration de logiciels pour l'établissement et la mise à jour rapide des cartes thématiques. (Résumé d'auteur

Background Concepts for a Rotating Harvesting Strategy with Particular Reference to the Mediterranean Red Coral, Corallium rubrum

A simple cohort model was used as the basis for selecting the appropriate periodicity and number of separate unit areas in a rotating harvest scheme for a sedentary species, the red coral, Corallium rubrum, in the General Fisheries Management Council for the Mediterranean area. The rotation period in years, and hence the minimum number of unit areas involved, was determined on the basis of the time to maximum biomass by a simple calculation of the yield-per-recruit type, requiring a knowledge of natural mortality and growth rates. Other criteria may be more important, however, and in general for a long-lived species, will result in shorter rotation periods. These criteria may include economic factors, criteria based on the preferred size or quality of product, or criteria that take into account the cumulative risk of illegal fishing of closed areas with time, hence the growing cost of enforcement as harvestable product accumulates. For red coral, although maximum biomass is predicted to be reached after some 15-44 years, the above considerations suggest that a rotation period ofsome 9-15 years would be close to optimal, taking into account a range ofthe above considerations. This article discusses the relative merits of rotating harvest schemes in contrast to quota management for sedentary and semi-sedentary resources or geographically isolated substocks ofa mobile resource, and concludes that this approach may have considerable potential as an alternative approach to resource management

Relative mobility determines the efficacy of MPAs in a two species mixed fishery with conflicting management objectives

Marine Protected Areas (MPAs) have been used to protect species in need of conservation and as a fisheries management tool. It has been suggested MPAs can benefit mobile stocks by protecting spawning grounds whilst also allowing yields to be maintained as mature fish move out of the protected areas. However, the robustness of this claim in mixed species fisheries has yet to be established. We use a simulation model to explore the efficacy of spatial closures and effort regulation when other forms of fishery control (e.g., Total Allowable Catches) are absent or non-enforced as ways of addressing management objectives that are difficult to reconcile due to the contrasting life-histories of a target and a bycatch, conservation species in a two-species fishery. The mobility of each stock in such a fishery affects the benefits conferred by an MPA. The differing management objectives of the two species can be partially met by effort regulations or closures when the species exhibit similar mobility. However, a more mobile conservation species prevents both sets of aims being met by either management tool. We use simulations to explore how spatial closures and effort regulation can be used to seek compromise between stakeholders when the mobility of one stock prevents conflicting management objectives to be fully met. Our results demonstrate that stock mobility is a key factor in considering whether an MPA can meet conflicting aims in a multispecies fishery compromised of stocks with differing life histories and mobilities