Abstract
SUMMARY: The stock concept plays a pivotal role in fisheries assessment and management. Stocks are defined according to biological, geographical, economic or socio-political factors. The General Fisheries Commission for the Mediterranean (GFCM) has established thirty management geographical sub-areas (GSAs) based on political and statistical considerations rather than biological or economic factors. Here, we present our view on the main biological and ecological aspects that should be considered for delineating different management units in the Mediterranean. We focus on the Balearic Islands (GSA05) as a case study highlighting its specificities compared to the adjacent coast of the Iberian Peninsula (GSA06), but the approach could be generalized to the problem of identifying stock boundaries in other areas. The work is based on published information from different marine disciplines such as geomorphology, ecology and fisheries, combined with the analysis of new data coming from official fishery statistics and scientific surveys. This approach avoids the important drawbacks (inconclusive results, high costs) of other time-consuming techniques used in stock identification, such as genetics. According to the information presented, we conclude that GSA05 should be maintained as an individualized area for assessment and management purposes in the western Mediterranean.
Highlights
The definition and identification of stocks play a key role in fisheries assessment and management.Stocks can be defined as intraspecific groups of randomly mating individuals with temporal or spatial integrity (Ihssen et al 1981, Waldman 2005)
We are not adverse to a re-evaluation of stock boundaries of General Fisheries Commission for the Mediterranean (GFCM)-geographical sub-areas (GSAs), we believe this should be carried out considering the entire set of current sub-areas rather than only individual ones. In case this debate is opened again within the framework of the GFCM, we present in this paper our view concerning the main biological and ecological aspects that should be considered for delineating different management units in the Mediterranean
We focus on the Balearic Islands (GSA05) as a case study, but our approach could be generalized to the problem of identifying stock boundaries for fisheries assessment and management in the Mediterranean
Summary
The definition and identification of stocks play a key role in fisheries assessment and management.Stocks can be defined as intraspecific groups of randomly mating individuals with temporal or spatial integrity (Ihssen et al 1981, Waldman 2005). The definition and identification of stocks play a key role in fisheries assessment and management. It is not easy to identify stocks because the delimitation of adjacent populations involves many difficulties, especially in the sea where there are no clear geographical barriers. Different methods have been used for stock identification such as genetics, morphometry, parasites and others (Cadrin et al 2005). Most of these techniques, are not useful for practical purposes owing to inconclusive results or high costs (Cope and Punt 2009). Fishery scientists have to adopt compromises to delineate entities for monitoring harvested stocks, such as management units or geographic areas. A variety of partly conflicting factors are used to delineate these entities, such as biological, geographical, economic, social or even political factors (Reiss et al 2009)
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