DURATION OF LARVAL AND SPAWNING PERIODS IN PAGRUS-AURATUS (SPARIDAE) DETERMINED FROM OTOLITH DAILY INCREMENTS

Counts of pre-metamorphic and post-metamorphic daily increments in the sagittae of settled juvenile Pagrus auratus were used to determine duration of the larval period and to back-calculate spawning dates. The duration of the larval period was 18-32 days, and was longer for snapper spawned early in the spawning season, when water temperatures were low, than for snapper spawned later in the season when temperatures were high. Sagitta size at metamorphosis was unrelated to duration of the larval period or temperature, and mean increment width during the larval period increased with temperature. These results suggest that metamorphosis is size- rather than age-dependent. Back-calculated spawning dates ranged from September to March, and peaked in November-January. Maximum spawning season duration was five months. Spawning onset was earlier when spring water temperature was higher than normal, and first spawning occurred at 14.8-15.6-degrees-C over three seasons, indicating that spawning onset is temperature-dependent.