HARD BOTTOM POLYCHAETA IN HUATULCO AND PU ERTO-ANGEL BAYS, OAXACA, MEXICO

Distribution, abundance and diversity of polychaetes were studied at t he tourism centers of Huatulco and Puerto Angel Bays, East Tropical Pa cific of Mexico. All specimens were hand-collected by SCUBA divers, al ong transects perpendicular to the coast. The areas sampled were chara cterized by a rocky bottom and corals of the genera Pocillopora. An in ventory of 71 polychaetes species is presented, based on 884 specimens , that belong to nine orders and 19 families. The dominant species wer e: Pseudovermilia occidentalis, Hydroides brachyacantha, Ceratonereis singularis, Trypanosyllis taeniaformis and Phyllodoce lamellifera, whi ch was present at all transects sampled. Over 24 species had a frequen cy greater than 60%. Diversity was higher in Puerto Angel (H'=3.05, J= 0.89), and abundance was higher in Cacaluta (292 organisms), followed by La Entrega (265 organisms). Species richness was similar for all lo calities except for El Maguey. The southern distribution range of Poly cirrus mexicanus and Pseudopotamilla debilis, previously set at the Se a of Cortez, is here extended to the Gulf of Tehuantepec. A cluster an alysis showed that Puerto Angel and Tangolunda had the highest similar ity (0.42). Both places share rock-coral facies, 16 species, and human environmental impacts. Caculata and El Maguey had the lowest similari ty (0.04) and the highest evenness, sharing only one species. When com pared to the mollusk communities at the same sites, the polychaetes st udied were less diverse but presented a higher evenness. Compared to C abo Pulmo, Sea of Cortez, a similar environment dominated by Pocillopo ra, the present polychaete community has a more diverse but less abund ant. However, two shared species, T. taeniaformis and Eunice lucei, ha d a similar abundance in these two areas.