Age and growth of two sympatric squid Loligo vulgaris and Loligo forbesi, in Galician waters (north-west Spain)

Age and growth of Loligo vulgaris and L. forbesi were studied by the examin ation of growth increments in 96 and 135 selected (white zone <10%) statoli ths, respectively. Squid were obtained by monthly sampling from the catches of commercial trawling and hand-jigs in Galician waters (north-west Spain) between February 1991 and October 1993. Mantle length (ML) of L. vulgaris ranged from 70 to 480 mm and varied between 70 and 685 mm in L. forbesi. A negative allometry between statolith length and ML or body weight (BW) was found in both species. Sexual dimorphism was apparent in both species, male s grew faster and longer than females. The statolith analysis suggests that growth patterns of L. vulgaris and L. forbesi in Galician waters are diffe rent. The exploited population of L. vulgaris was composed of two groups: o ne formed by individuals hatched in winter-spring and another by specimens hatched in summer-autumn. Squid hatched in winter-spring reached larger siz es at the same age than those hatched in summer-autumn. These two groups we re also observed in L. forbesi. However, squid of this species hatched in w inter-spring were smaller than those hatched in summer-autumn at the same a ge. Reasons for this discrepancy are discussed. The life span of L. vulgari s was about one year whereas the life span of L. forbesi extended to 18 mon ths.