Understanding the early life history of fish is essential for investigating population dynamics, spatial connectivity and stock structure, which contribute to developing highly-resolved fishery management strategies. This study considered King George whiting (Sillaginodes punctatus), the most significant inshore fishery species of southern Australia. It explored the early life history of recruits to a significant nursery area in Gulf St. Vincent, South Australia. Post-larvae were sampled fortnightly throughout the July to November settlement period and the early life history retrospectively reconstructed using otolith microstructure and elemental chemistry. Back-calculated spawn dates covered a four month period from March through June, whilst spawning during a short, three week, period in May contributed most to recruitment. Trace element chemistry analysis considered the natal origin of the same fish and identified two different multi-elemental signatures that related to fish spawned up until April, and those spawned thereafter. This within-season temporal change in otolith chemistry reflected higher ⁸⁸Sr and lower ⁷Li later in the spawning season, and suggested two possible scenarios: either a change in environmental conditions that considerably influenced otolith chemistry; or there were two different natal origins. These findings emphasize the importance of considering within-season variability in life history studies.