Reproductive mode and spawning information based on gonad analysis for the King George whiting (Percoidei:Sillaginidae) from South Australia

Abstract

The reproductive biology of the King George whiting, Sillaginodes punctata, was investigated for populations at two localities in South Australia. Analyses involved determination of gonadosomatic indices, macroscopic staging of gonads, size frequencies of oocytes, spawning fractions of females, and batch fecundities that were related to fish size and age. Size–frequency distributions of oocytes, measured from histological slides and whole preserved oocytes, were multi-modal but were continuous amongst development stages. All development stages of oocytes co-occurred in some gonads, and hydrated oocytes and post-ovulatory follicles also co-occurred. Such characteristics suggest that the King George whiting is a multiple batch spawner with asynchronous development and indeterminate fecundity. Spawning occurred at least through the months of March–May, with a peak in April. On one occasion spawning occurred in the early afternoon on a flooding tide. Fish ranged in age from 3 to 17 years, and most, regardless of sex or size, showed active gonad development. Estimates of batch fecundity ranged from 5250 to 152191 hydrated oocytes per ovary, and were linearly related to fish weight and length, but less well to age. The linear relationships between batch fecundity and fish size differed significantly between the two localities.