Girella tricuspidata is widely distributed and harvested by recreational and commercial fishers along the coastline of eastern Australia. The present study examined variability in the reproductive biology and growth of individuals within populations of G. tricuspidata across 3 estuaries (Clarence, Tuggerah and Tuross) and assessed population connectivity via a large-scale tagrecapture study in which fish were tagged across 9 estuaries. Spawning occurred predominantly between June and September in the Clarence River and between October and January in the Tuross River, suggesting that spawning occurs later in the year at higher latitudes. The recruitment of young to nursery grounds was spatially and temporally variable. G. tricuspidata are group-synchronous spawners, and the estimated batch fecundity was positively correlated with fish length. The estimated length and age at which 50% of G. tricuspidata attained reproductive maturity was similar for both sexes: ~286 mm fork length (FL) and 4.1 yr for males and 295 mm FL and 4.5 yr for females. G. tricuspidata were aged using otoliths to > 26 yr, whereas the reading of scales consistently underestimated the age of fish older than 5 yr. Growth was flexible but varied significantly between sexes and among estuaries; females grew faster than males and attained a larger asymptotic length in the Clarence and Tuross Rivers but not in Tuggerah Lake. Growth was rapid for both sexes until 4 to 5 yr of age, after which it slowed. Of the 6871 G. tricuspidata tagged, 15% were recaptured, with 96% of these fish recaptured in the estuary in which they were initially tagged. The recaptured individuals that migrated between estuaries predominantly displayed a northward movement into the prevailing coastal current, which is probably a life-history tactic to facilitate wide dispersal of eggs and larvae along eastern Australia.

The dietary composition and partitioning of food resources between five sympatric species of Platycephalidae inhabiting the coastal waters of New South Wales, Australia was investigated. Samples were collected monthly between March and November 2007 onboard commercial ocean prawn trawlers based in the ports of Yamba and Newcastle. Monthly percentage weight contribution of 12 prey categories was analysed to determine if diet was influenced by the variables: species, location, depth, size and maturity. Of the 959 stomachs from the five species examined, 28-54% contained prey. All Platycephalid species primarily consumed teleosts, however the diversity of prey and the proportion each prey type contributed to the overall diet varied substantially between species. Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni and Ambiserrula jugosa were generalist carnivores and consumed prey from a wide variety of phyla including teleosts, crustaceans, polychaetes, molluscs and echinoderms. In contrast, Ratabulus diversidens were primarily piscivorous.Partitioning of prey resources between species was more evident in waters at Yamba than at Newcastle. Differences in diet between locations were considered a result of differential prey exploitation rather than shifts in the suite of prey consumed. Dietary composition was observed to be influenced by size, maturity status and depth however these differences were not observed for all species.

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Summary 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 (L50) and age (A50) 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 98.5 cm TL (7.5 kg), and the oldest 16 years, whereas the largest male was 61.5 cm TL (1.58 kg) and 11 years 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 30–40 cm TL protect approximately 3–9% of the female spawning population. Alternative management options, including harvest slot sizes, need to be investigated and tested.