Fish assemblages in the bycatch of bottom shrimp trawls on the west side of the Gulf of California, Mexico

Abstract

The assemblage of the fish species obtained as bycatch in trawl nets on the Gulf of California in 2004, 2005 and 2007 was studied. Sampling was carried out during July and August at a series of stations along the coast of Sonora. The criteria for the most important fish species caught were drawn from abundance and frequency of occurrence and weight, using various ecological indices (index of relative abundance, biological value index and index of relative importance). After identification, these species and their abundances were used to define study groups based on similarity matrices and Ward's clustering method. We analysed 125 fish hauls containing>19,000 organisms, representing 243 species (fish, crustaceans, molluscs and echinoderms). There were 28 dominant species, most notably Urobatis halleri, Synodus scituliceps, Eucinostomus argenteus, Diplectrum pacificum and Haemulopsis nitidus. Cluster analysis, based on latitude, and bathymetry showed three station groupings. The first was characterized by species from the northern region of the Gulf with a bathymetric distribution>25 m. The second was dominated by species from the central to southern region from depths<25 m. The third was a transitional group with species found between the central and southern Gulf from depths of 10 to 45 m. Most fish assemblages consist of species with wide distribution within distinct biogeographic provinces, which showed a major change in the association, frequency and absence of species from north to south, indicating a variety of habitats in the Gulf of California.

Keywords:

• Fish
• Gulf of California
• zoogeography
• cluster analysis
• ecological indices

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We thank the Fisheries Ecology Laboratory of CIBNOR, especially Eloísa Herrera-Valdivia and Rufino Morales-Azpeitia. Joaquin Magaña and Karen Link translated the manuscript. Ira Fogel of CIBNOR provided final editorial services. Funding was provided by various grants (SAGARPA-CONACYT grant 2003-002-089, PRODUCE Sonora, CIBNOR grant EP1.2). J.E.V.H. was supported by CONACYT grant 84944 (FLUCARGOC II). INAPESCA greatly assisted by obtaining the samples for analysis. C.H.R.Q. is a recipient of a doctoral fellowship from CONACYT.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark