Length and age structure in commercial catch samples of the pismo clam Tivela stultorum (Mawe, 1823), from Playa San Ramon, B.C., Mexico

Abstract

Age was determined in 1,368 pismo clams (Tivela stultorum, Mawe, 1823) by growth ring analysis, in commercial catch samples collected from July 1978 to February 1983. Approximately 25 age classes were present between 1978 and 1980, divided into two modal groups (younger and older than 21 years), suggesting the occurrence of wide fluctuations in abundance. During the study period a general decreasing trend was observed in average length (from 12.2 cm in 1978 to 10.9 cm in 1983) and age (from 24.9 years in 1978 to 17.9 years in 1983), probably as a result of overexploitation.