ABSTRACT: Two hypotheses regarding the origin of post-larval Sillaginodes punctata that recruit to nursery areas in South Australia were assessed. These were that post-larvae originate either hundreds of kilometres to the west and are delivered by weather-determined ocean currents or they originate from numerous spawning grounds located only <150 km from numerous nursery areas. The hypotheses were tested in 2 ways. We compared recruitment rates and early life-history characteristics amongst post-larvae sampled at 4 sites located up to 500 km apart. Recruitment rates, size structures of recruits and age, size and growth rates of recently-settled fish did not reflect systematic variation amongst sites, suggesting that recruitment was determined at a local, rather than regional scale. We also used numerical hydrodynamic modelling to identify larval advection pathways and possible spawning locations, using larval duration and capture site as input to the model. This modelling suggested that recruits originated at spawning locations that were only a short distance from each nursery area. Results from both studies suggested that the South Australian population is divisible into numerous, discrete, self-recruiting populations, which contrasts with the situation in Victoria where the population constitutes a single large stock. This difference is a likely consequence of regional differences in current regimes, and the influence on larval advection.

KEY WORDS: Stock structure · Larval advection · Hydrodynamic numerical modelling · Otolith microstructure · South Australia · Sillaginodes punctata

Published in MEPS Vol. 199 (2000) on June 26
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 2000