| Resumo: |
The gatuzo, Mustelus schmitti, lives in the Southamerican Atlantic coastal waters from up to 23°S (Brazil)down to 47°S (Argentine), and is the greatest species of the Bonaerense and North Patagonian shores. This species is the most exploited elasmobranch of this region, within the last six years catch has exceeded 10,000 t per year and it is vulnerable to overexploitation due to reproductive aspects, with a low rate of changes, as well as distribution patterns. In order to relate size distribution and nursery areas, and environmental temperature and salinity variability, were obtained within six INIDEP 'Coastal Project' research cruises from 34° to 42°S from boundaries to 50 mts isobaths, during the spring seasons between 1994 to 1997. Cluster analysis were made during each research cruise to associate fishing hauls according to size range and similar mode. From these results, El Rincón and Rioplatense areas were compared: size structure and distribution related to temperature and salinity; juvenile and adult rates, nursery areas; sex rates and abundance. Examined data allowed to determine that size distribution on the Rioplatense area is clearly bimodal for the four research cruises studied, differing in El Rincón area, where size distribution is homogeneous and juveniles predominate, while in the northern area those are adults (up to 59 cm). Regarding sex rates males prevail in both areas, from 1.2:1 in El Rincón and to 2:1 in the Rioplatense area. On a first attempt, cluster results on size allowed to determine growth parameters, with the 'Bhattacharya method', relative rate and growth curves. Results show a relation between analyzed environmental variables, specially salinity and species size distribution.
Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales.
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