Preliminary considerations of the status of elasmobranchs in the Italian waters

Few formal stock assessments of elasmobranchs have been conducted in the Mediterranean. This because the information needed is not enough detailed and precise. In recent years, also in the Mediterranean Sea a major concern on the exploitation status of the stocks, belonging to this group, is increased and scientists and managers have paid a major attention on the elasmobranchs stocks and on their management. More effort was dedicated for gathering the necessary data and hence the situation is improving even though is still not satisfactory. Information on landings is now available but time series are still too short. Data on age structure of catches is partial and often does not regard all the fisheries in which those stocks are involved. The estimates of biomass and exploitation rates are linked with the construction of a formal stock assessment model. In the case of elasmobranch stocks in the study area, the lack of such information require the use of alternative approaches for giving indication on the stock‟s status and for management advice. The choice of an assessment approach is necessarily driven by the available data. In order to collect data on the fish population, the European Union has activated a scientific cruises (Data Collection Framework) using bottom trawl nets and a catch assessment survey allowed the collection of data, necessary for a preliminary assessment of the stocks status. In this paper, preliminary results of a demographic analysis and yield per recruit analysis were used for the definition of the status of the stock regarding its capacity of self-renewal. The analysis was performed only for 4 stocks (Raja asterias, Raja clavata, Scyliorhinus canicula and Galeus melastomus), which are the better known stocks regarding natural history features and fisheries. The results of the demographic analyses, using Leslie matrices and Y/R, suggest that the exploitation with the current levels of F of all the species and the too early age of first capture (tc<1) do not guarantee sustainability for the stocks. Such results have to be considered as preliminary considering the quality of data used for the estimation of reference points and current Fs. It was assessed the influence of the estimates of the vital rates fecundity at age and mortality rates on the population growth rate using an elasticity analysis. For all the species the elasticity analyses suggests that the first ages are the main responsible of changes in the population growth rate. For the studied species it is concluded that management measures aimed at protecting juveniles (e.g., mesh. size increase, nursery and breeding areas closures) should provide greater benefits to the population than a strategy aimed at protecting adults.