First Observation of the Tope Shark, Galeorhinus galeus, in the Northern Patogonian Gulfs of Argentina (Elasmobranch Fisheries - Poster)

The artisanal fishery in the gulfs of San Matias, San Jose and Nuevo, Argentina (42°-43°S; 64 °-65°W), represents an important productive activity that accounts for 400 jobs (fishermen, factory workers, retail sellers, etc.) in the city of Puerto Madryn, of around 50 0 00 inhabitants. The objective of this study was to test a productive alternative for artisanal fishermen in order to increase their catches and profits. The aim of this paper is to provide the first information on general aspects about one of the target species, Galeorhinus galeus, in the northern Patagonian gulfs. The species mean lengths obtained in the San Jose and Nuevo Gulfs were similar (Lt = 132 cm). The individuals caught in the platform were larger (Lt = 141 cm) than those caught in the gulfs. Less than 10% of the total catches in all the fishing grounds were females, their total length ranged from 110 to 126 cm and their Hepatic Index values ranged between 0.7 and 0.9. These data show that females were an incidental catch and that they were all juveniles. The total length of the males ranged from 105 to 150 cm and the Hepatic Index values were between 0.7 and 1.1. The gonads showed males were adult with traces of maturity, according to a first maturity length of 112.5 cm. According to these results, a tope shark fishery in the Nuevo Gulf during summer would be a complement to artisanal purse seining and bivalve extraction. The absence of gravid females allows to think of a sustainable exploitation, while the capture volumes stay relatively low. Chiaramonte (2000) mention the possible overexploitation of the resource in the fishery with base in the port of Quequen, also outlines the possible collapse of the fishery in terms of the economic profitability. The development of a longline fishery in the gulf Nuevo should maintain the character of artisanal and of small scale, in a such way of controlling the fishing effort and the number of hooks per boats.