Age and size-at-maturity of Loligo vulgaris from Portuguese waters
were evaluated in order to explain its complex population structure, which
is strongly influenced by continuous spawning. Age was obtained by increment
counting in statoliths. Maturity ogives by age group indicated that males
mature one month earlier (at 277 days) than females (at 298 days). Females
mature at a ML50% of 17.6 cm, while males mature at smaller sizes. The
later, however, showed a high degree of complexity in the size at maturity
with evidence of two size at maturity groups. In both sexes, maturity was
ultimately found to be primarily dependent on size rather than age. The
effect of hatching season on age-at-maturity, size-at-maturity and
reproductive investment was analysed by comparing two groups of squid
hatched under distinct environmental conditions, namely the temperature
during the first 3 months of life, the cold cohort (CC), hatching between
December and March and the warm cohort (WC), hatching between May and
September. Significant differences were found between cohorts on
age-at-maturity, size-at-maturity and reproductive investment, giving
indication of the environmental influences on sexual maturity. CC squid
mature ca. 2 months later in life than WC squid and at a significantly
larger size. The reproductive investment as measured by GSI was higher in
the WC squid. Much of the variability in age and size-at-maturity of females
in the population was due to differences between cohorts but this was not
the case for males.