Gastropod mollusks from the continental shelf off Jalisco and Colima, Mexico: Species collected with a trawl net

This study examines the distribution and abundance with respect to depth and type of substratum of 86 gastropod species collected from the Pacific continental shelf off Jalisco and Colima, Mexico, in August 1988. Sampling was performed with a trawl net at 22 stations, at depths of 18 to 112 m. A total of 582 individuals pertaining to 42 genera, 25 families, 4 orders and 3 subclasses of gastropods were collected. Abundance of gastropods was similar between 18 and 83 m, but the number of live individuals decreased between 41 and 60 m. Deep (61-83 m) stations registered the lowest diversity; however, the number of species collected alive decreased with depth. No gastropods were collected at stations deeper than 83 m. The number of individuals and species also varied with the type of substratum. Greater heterogeneity of the sediments was found at the shallower stations (18-60 m) with medium sand, sandy silt and silty clay substrata. The greatest number of species were collected at stations with sandy silt and medium sand substrata. Total abundance was notably smaller in medium sand, while the abundance of live gastropods was higher in silty clay substratum. The seven most abundant species represented 51.2% of all of the individuals. Most of these species are of commercial interest, in particular those of the genera Fusinus, Hexaplex, Ficus, Harpa, Cantharus and Bursa