Temporal variation in the early life-history characteristics of the King George whiting (Sillaginodes punctata) from analysis of otolith microstructure

Abstract

This study describes the duration of the settlement season, the somatic and otolith growth rates, and presettlement durations for Sillaginodes punctata at Barker Inlet, South Australia. The settlement season was from June to November, with settlement occurring in two phases over this period. Somatic growth rates ranged from <0.1 to 0.25 mm day^-1 depending on age and time of year, making size (SL) a relatively poor indicator of age. Alternatively, otolith size (OL) was strongly related to age, but the linear relationships varied systematically among sampling occasions. Because of variation in somatic growth rates, the SL-OL relationships were relatively poor. The biological intercept method was used to back-calculate fish sizes from otolith increment widths for three samples of fish. These growth trajectories differed considerably, two being logistic in shape and the third being an exponential relationship. Presettlement durations increased from 80 to 130 days between June and September and were inversely related to growth rate. Settlement competence is related more to size than to age. The broad natural variation in early life-history characteristics is likely to relate to water temperature regimes along larval advection pathways through the long settlement season.