Eduardo Ríos-Jara, Ernesto López-Uriarte, Cristian M. Galván-Villa
American Malacological Bulletin 26 (1/2), 119-131, (29 December 2008) https://doi.org/10.4003/006.026.0212
KEYWORDS: Bathymetric patterns, diversity, dominance, evenness, benthos
A survey for bivalves was conducted at 25 sampling stations on the Mexican Central Pacific shelf off Jalisco and Colima, during the summer of 1988. The bivalves were sampled with a Van Veen grab at 16 stations with medium sand, sandy silt, and silty clay substrata at depths between 18 and 112 m. A total of 5,196 individuals belonging to 59 genera and 95 species of bivalves were found. A systematic list is provided with the relative abundance and density (individuals/m2) for each species and information on depth, type of substratum, bottom water temperature, and oxygen concentration for each station. The twelve most common species (>100 individuals/station) in descending order of abundance were: Nuculana laeviradius (Pilsbry and Lowe, 1932), Crassinella pacifica (C. B. Adams, 1852), Corbula nasuta G. B. Sowerby I, 1833, Anadara adamsi Olsson, 1961, Parvilucina approximata (Dall, 1901), Nucula declivis Hinds, 1843, Corbula ira Dall, 1908, Radiolucina cancellaris (Philippi, 1846), Cyclopecten pernomus (Hertlein, 1935), Nuculana lobula (Dall, 1908), Parvilucina mazatlanica (Carpenter, 1857), and Gouldia californica Dall, 1917. The bathymetric patterns in the abundance and species composition of the bivalve community and their relationship to environmental parameters are discussed. The structure of the assemblages differed with depth, with peak abundances and species richness (1) between 24 and 40 m with medium sand and sandy silt substrata and (2) at intermediate depths between 71 and 74 m, with sandy silt and silty clay substrata. The species characterizing shallow, intermediate, and deep zones were the most abundant or those exclusive of each zone. Diversity, dominance, and evenness decreased at the deeper stations. The distinctive species composition of these zones may be the result of variation in depth, oxygen concentration, and substratum.