Comparison of the spawning patterns and fisheries biology of the sardine, Sardinops sagax, in temperate South Australia and sub-tropical southern Queensland

Abstract

South Australia is the centre of the Australian distribution of Sardinops sagax, whereas southern Queensland is the northeastern edge of its local range. In South Australia, eggs were collected during all months and the peak in abundance coincided with the upwelling period in summer–autumn (January–April). In contrast, eggs were collected from southern Queensland only during winter–spring (August–November), when water temperatures fell below 23 °C. In South Australia, eggs were found throughout shelf waters, whereas in southern Queensland most eggs were collected from a small area between Noosa Heads and Caloundra. The South Australian fishery was confined mainly to the waters of southern Spencer Gulf and the Coffin Bay Peninsula, and the Queensland fishery was centred on the area of high egg density. Catch rates in the South Australian fishery were high throughout the year, whereas low catch rates were recorded in southern Queensland outside the spawning season. In South Australia, 50% of males and females were mature at approximately 146 and 150 mm FL, respectively. Over 70% of fish in all size classes collected from southern Queensland were sexually mature. Fish less than 145 mm FL comprised over 30% of South Australian catch, but less than 3% of fish taken from southern Queensland. Evidence is consistent with the hypothesis that S. sagax is a widely distributed resident of South Australian waters, but only migrates into southern Queensland during winter–spring to spawn.