Nassarius gayii (Kiener, 1834) (Gastropoda, Prosobranchia) in San Antonio harbour, central Chile

Abstract

Monthly samples of Nassarius gayii from San Antonio (33°36'S; 71°38'W), were obtained with a Petersen grab, in eigth stations between three and 20 m depth (June 1978 to september, 1979). Average of temperature, salinity and concentra! ion from surface werc 19,2°C , 32,3%o. and 4,8 ml/l. Al 20 m depth values were 12,6°C, 33,9%. and 4,3 ml/l respectively. Length frecuency distribution for cach station and month, Jength-wet wcigth (Lt/Pht), lcnglh- total dry weigth and length-shell and opercle dry weigth (L/Psc and op.) were calculated. Seasonal variation of density, dry biomass and pondercd average weigth of thc sampled population were analyzed. Station 7 had the higher percentage of juveniles, indicating a probable recruitment arca. Station 8 had the higher number of adults (73.1 %.). The values of density and biomass were between 22,8 ind/m2 and 6,5 x 10-3 g in June, 1979, and 620 ind/m2 and 31 x 10-3 g in October, 1978. The higher mortality was observed in July, because of its lower values of populations density. The recruitment probably occurs in spring and fall. The monthly dry biomass reached a peak in October, 1978 with 329 g and a population density of 43 individuals. In 1979 the peak was in April with 280 g annual 380 individuals. lt was recognized three medal groups of Nassarius gayii suggesting age 2 and 3 years.