عنوان

GCP/RER/010/ITA/MSM-08 (MedSudMed Technical Documents n°8)
Contribution to Guidelines for Age Determination of Chondrichthyes fish from the Mediterranean Sea (application to selected species)

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The MedSudMed workshop on age determination of selacean fish was held in Mazara del Vallo, Italy, from 22 November to 1 December 2004. It was attended by participants from Tunisia, Italy and Malta. The main objective of the workshop was to provide an overview of techniques currently used in the MedSudMed Project area for preparation and reading of spines and vertebrae of a series of cartilaginous fish species (Centroscymnus coelolepis, Cetorhinus maximus, Carcharhinus plumbeus, Galeus melastomus, Scyliorhinus canicula, Mustelus mustelus, Rhinobatos cemiculus, Rhinobatos rhinobatos, Raja clavata, Squalus blainvillei, Chimaera monstrosa). The course provided training and joint preparation and interpretation of samples provided by the participating institutes. Participants had agreed on a common protocol for preparation of the samples prior to the course. Direct observation of vertebrae and spines was conducted, along with tests of two methods for enhancing the appearance of the growth bands (red alizarin and cobalt nitrate). On the basis of the laboratory work and of the relevant bibliography available, trials were performed to identify the most relevant techniques for each species studied. This document details the work done during the workshop and provides general guidelines for cartilaginous fish age determination, as well as the limits of the methods currently used and improvements that could be made in the near future. It appeared that direct observation gave good results for all species except C. coelolepis. Red alizarin and cobalt nitrate staining procedures also improved the appearance of growth patterns except for C. plumbeus, Centroscymnus coelolepis and Scyliorhinus canicula and Galeus melastomus. Good results were obtained for some species (C. plumbeus, and G. melastomus), according to the size of the observed individuals. Further investigations are needed; in particular, larger samples should be examined to confirm the methods used and to provide detailed guidelines to be used at the regional level.