Aspects of the fishery and feeding ecology of the dominant ray species in Bahía Almejas  (B.C.S., México)

 Joseph J. Bizzarro (Expositor), Gregor M. Cailliet

Pacific Shark Research Center. Moss Landing Marine Laboratories. 8272 Moss Landing Rd. Moss Landing, CA. USA.95039. (831) 771-4419. Correo electronico: jbizzarro@mlml.calstate.edu

Sampling of rays from the Almejas Bay (BCS, Mexico) fishery for diet composition was conducted at Puerto Viejo during summer months from 1998-2002. Of over 4,000 elasmobranchs landed among at least 22 species, four species (Rhinobatos productus, Dasyatis dipterura, Narcine entemedor, and Gymnura marmorata) comprised 91.7% of the catch. Sex ratios, length frequencies, cpues (number/vessel) and a description of the fishery will be presented. This fishery peaked in June (total cpue = 42.7), targeting mainly gravid female R. productus (cpue = 21.4) and N. entemedor (cpue = 10.7). In August, the fishery operated at a diminished capacity (total cpue = 22.3), subsisting primarily on resident populations of D. dipterura (cpue = 9.5) and G. marmorata (cpue = 4.7). Samples were collected from over 2,200 specimens for dietary analyses. Rhinobatos productus preyed primarily on crustaceans (shrimp and crabs) and, to a lesser extent, polychaetes with fishes also taken by large specimens. All sizes of G. marmorata consumed exclusively teleost fishes with a single occurrence of a squid. The diet of D. dipterura consisted mainly of epibenthic and infaunal invertebrates, including pea crabs, small bivalves, and polychaetes. Narcine entemedor feed primarily on polychaetes, sea slugs, and eels. Differences in diet appear to be correlated with differences in morphology of the feeding apparatus.