IN-SITU MONITORING OF THE DURATION OF EMBRYONIC DEVELOPMENT IN THE SQUID LOLIGO GAHI (CEPHALOPODA: LOLIGINIDAE) ON THE FALKLAND SHELF

Nineteen egg masses of the Patagonian squid Loligo gahi were monitored by divers at a near shore site (13‐18 m depth) located at the entrance to Port William, East Falkland, in the Southwest Atlantic over three summer and two winter periods in 1999‐2002. Six egg masses were monitored from early stages of embryogenesis until hatching. The duration of embryonic development varied from 51‐65 days in summer to 125 days in winter, while the daily-accumulated temperatures (DAT) required for complete embryogenesis varied rather less (521‐596° days). Hatching from one egg mass lasted at least 10 days in summer. The size and shape of the hatchling statolith matches the size and outline of the first stress mark in the juvenile statolith so confirming the ‘natal’ nature of the mark. The 4‐6-month difference in spawning time between the two main cohorts of L. gahi (May‐June in the autumn-spawning cohort and October‐November in the spring-spawning cohort) diminishes to just a 2‐3 month difference in hatching time (September‐October and December‐January, respectively). This allows the recruits of both cohorts to target the pronounced spring and early summer zooplankton bloom in the Southwest Atlantic.