Age and growth studies of oceanic squid, Sthenoteuthis oualaniensis using statoliths in the South China Sea, Area III, Western Philippines

Abstract

Studies on age and growth using statolith of oceanic squids, Sthenoteuthis oualaniensis collected from Western Philippines, South China Sea, Area III have been conducted from 7 April - 19 May, 1998 by MV SEAFDEC Cruise No. 50-4/1998. A total of 1,707 squids were sampled and measured onboard. 74 statoliths which consist of 53 statoliths from female specimens and 21 from male specimens were extracted and processed using statolith ageing techniques with the body mantle length range from 107 - 217 mm and 115 - 167 mm, respectively. The male is smalled than the female where the male does not exceed 180 mm and the the female can grow upto 260 mm.There is slighly a different dimension of growth at the statolith microstructure between the male and female specimens. In the ground statolith, growth increments were examined and grouped into four growth zones distinguished mainly by the width of the increments. It was found that the male exhibit slower growth and maturation occur at the same time with the female but at smaller size. The age of the male and female ranged from 135 - 259 days and 95 - 275 days, respectively. The life span of the species was considered within one year. It was also observed that the putative microcohort of the female could be explained from the length frequency distribution of the immature and mature female and a pool data of length frequency distribution from all stations.