Composition, abundance and distribution of holoplanktonic polychaetes from the expedition “El Golfo 6311-12” of Scripps Institution of Oceanography

Abstract

Holoplanktonic polychaetes from the zooplankton samples taken during El Golfo 63/11-12 Cruise conducted by Scripps Institution of Oceanography, University of California, San Diego, were studied. Eighty-seven samples were reviewed, which were collected over an extensive area including both coasts, western and eastern, of the Baja California peninsula, the continental coast of the Gulf of California, and some localities in the northeastern Pacific. Samples were obtained in the epipelagic region by oblique plankton hauls (using conical nets 5 m in length, 0.5 and 1.0 m in mouth diameter, and 0.50 mm mesh), from 47 localities. Two hundred and twenty-three polychaetes belonging to 17 species of six holoplanktonic families were identified. Ecological characterization of the species showed that Phalacrophorus uniformis, Typhloscolex muelleri, Sagitella kowalewski and Travisiopsis dubia were dominant, Tomopteris nationalis was constantly seen, and the remaining twelve species were rare. The richness and distribution of these holoplanktonic worms were poor compared with other collections obtained by different cruises in the adjacent offshore regions of the survey area. These results are discussed from a biogeographical point of view.