AGE AND GROWTH OF THE SQUID STHENOTEUTHIS-PTEROPUS (OEGOPSIDA, OMMASTREPHIDAE) FROM THE CENTRAL-EAST ATLANTIC

An investigation was carried out on the morphology, growth and microstructure of statoliths of 833 specimens of Sthenoteuthis pteropus (Steenstrup) mantle length (ML): 2-548 mm collected in the open waters of the Gulf of Guinea in 1984-88. Statolith morphology is similar to that of other species of the subfamily Ommastrephinae and is similar to the sibling species S. oulaniensis. Statolith development includes five stages resembling those of Illex illecebrosus and other ommastrephids. Statolith growth is characterized by negative allometry. Increments visible in ground sections of statoliths can be grouped into four main growth zones, differing mainly in colour and increment width. Age and growth rates of S. pteropus were calculated using increment counts. The life span of females of all size groups does not exceed 1 yr, that of males is 1-2 months shorter, probably due to preliminary mating. Instantaneous relative growth rage (G) of paralarvae is high (up to 16% of body weight (BW)). G values for juveniles decline, but remain relatively high (7-8% BW). Juveniles attain 100-1 10 mm ML by age 100-1 10 days. G values for adults are the lowest (1.8-2% BW), but daily growth rates reach maximum values (40-70 g per day in large females of 450-500 mm ML). Each ontogenetic phase of S. pteropus corresponds to features of morphology, growth and microstructure of the statolith.