Analysis of distribution and abundance of the stingrays Dasyatis geijskesi and Dasyatis guttata , caught with fish trawlnets in experimental fisheries off northern Brazil

Abstract

Between the months of February, 1998 and December, 1999, six research cruises were carried out on board R.V. Almirante  Paulo Moreira, which belongs to CEPNOR/IBAMA. This vessel uses as fishing gear a fish otter trawl spread out by iron doors During  the surveys data were collected about the abundance and distribution of two stingray species of the family Dasyatidae, both of them  with a wide distribution along the coast.  Dasyatis geijskesi , in spite of being an endemic species of northern Brazil, did not show any  substantial catch volume. What the research results did show was the predominance of  Dasyatis guttata , which accounted for about  90% of the total catch in weight. As to production seasonality, the highest values took place during the dry period, in the months from  August to December. For studying species distribution down the water column three depth strata were set up, namely < 50 m, 50 - 100  m and > 100 m, where catch per unit effort and catch per unit area values were estimated, and whose averages were 338.00 kg per hour  and 18.56 kg per hectare, respectively. The biggest overall values were recorded in depths over 100 m for the species  D. guttata .