Spawning, maturity, growth and movement of Platycephalus fuscus (Cuvier, 1829) (Platycephalidae): fishery management considerations

The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and commercial fishers throughout its endemic distribution along eastern Australia. This study indicates that the species has an extended spawning period throughout the austral summer, with females in spawning condition occurring in lower estuarine and coastal waters. Total length (L-50) and age (A(50)) at which 50% (+/- 1 SE) of the population was mature was 31.72 (+/- 1.08)cm TL and 1.22 (+/- 0.44)years for males and 56.75 (+/- 0.60)cm TL and 4.55 (+/- 0.13)years for females. The von Bertalanffy growth parameters differed significantly between sexes; females grew faster and attained a greater maximum TL and age than males. The largest female was 98.5cm TL (7.5kg), and the oldest 16years, whereas the largest male was 61.5cm TL (1.58kg) and 11years of age. A tag-and-release study identified the exchange of sub-adult and mature-sized individuals among estuaries. Determinations of length-based management regulations for the species are compounded by the large gender-based differences in growth and length-at-maturity. Current minimum legal lengths of 30-40cm TL protect approximately 3-9% of the female spawning population. Alternative management options, including harvest slot sizes, need to be investigated and tested.