A BIOLOGICAL SURVEY OF BAHIA DE LOS ANGELES, GULF OF CALIFORNIA, MEXICO. II. BENTHIC POLYCHAETOUS ANNELIDS. Donald J. Reish Abstract. The benthic polychaetous annelids of Bahia de los Angeles were studied quantitatively in April 1962 and October 1963. Distribution and sediment preferences of the principal species are summarized. Of the 112 species encountered, ninety were previously unreported from the Gulf ol California. Six new species are described: Microphthalmus riojai, sp. n., Aricidea {Aricidea) rosea sp. n., Prionospio longibranchiata sp. n., Pectinaria (Pectinaria) hartmanae sp. n., Euchone barnardi sp. n., and Euchone cortezi sp. n. In April 1962, 3 9,470 specimens were collected; in October 1963, 7,100. The cause of this reduction is unknown, but high summer water temperatures may be involved. Previous reports of polychaetes from the Gulf of California are summarized. Resumen. Los Anelidos Poliquetos bentonicos de la Bahia de los Angeles fueron estudiados cuantita-tivamente durante Abril de 1962 y Octubre de 1963. Se detalla la distribucion de las especies principales, y las preferencias que presentan respecto a los distintos sedimentos. De las 112 especies registradas, solamente 22 han sido observadas previamente en el Golfo de California. Se incluye la descripcion de seis especies nuevas: Microphthalmus riojai sp. n., Aricidea (Aricidea) rosea sp. n. Prionospio longibranchiata sp. n., Pectinaria (Pectinaria) hartmanae sp. n., Euchone barnardi sp. n., y Euchone cortezi sp. n. En Abril de 1962 se obtuvieron 3 9,470 ejemplares, y solamente 7,100 en Octubre de 1963. Se desconocen los factores causantes de esta enorme diferencia numerica; sin embargo, se considera que las temperaturas elevadas registradas durante el verano, pudieron ejercer una definida influencia en ese fenomeno. Tambien se incluyen las observaciones previas correspondi-entes a los Poliquetos del Golfo de California. Early accounts of polychaetes from the Gulf of California have been summarized by Rioja (1941). Subsequent information has been added by Rioja (1943; 1947a, b), Hartman (1944a, 1950), Treadwell (1942), Fauvel (1943), Woodwick (1961), and Parker (1963). However, no quantitative studies have been made. Previous quantitative studies of eastern Pacific polychaetes by Reish (see references) have dealt with nearly all the principal bays from Morro Bay, in central California, south to Bahia de San Quintin, Baja California. This paper, which summarizes the quantitative data on the distribution of polychaetes in Bahia de los Angeles, a small bay on the west side of the Gulf of California, and compares the fauna ecologically and zoogeographically with that of similar areas in southern California, extends the area of quantitative studies into a geographically disjunct area. The specimens on which this report is based were collected by the Beaudette Ioun-dation in April 1962 and October 1963 (see Barnard and Grady, 1968). Quantitative samples were taken at 79 stations in April 1962 and 82 stations in October 1963 (Fig. 1) using a modified size-one Hayward orange-peel bucket which samples an area of 0.06m-. Three dredge hauls were made in April 1962. Samples were brought back to the base camp, washed through a 0.5 mm screen and preserved in formaldehyde for later sorting. I wish to thank Dr. J. Laurens Barnard for making the collections avail-able to me. My research was supported in part by a grant from the National Science Foundation (NSFG-20909). Chemical and Physical Data. — Salinity was measured throughout the bay in April 1962, April 1963, and October 1963 at water depths of 0, J, 10. 20, 30, 40, .md JO meters. All values ranged from about 3 5.0 to 3 5.5 00, which coincide with the salinity values given for the upper Gulf of California by Parker (1963). San Diego Soc. Nat. Hist., Trans 1$ (7): 67-106, 17 June 1968.
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