Reproductive Biology of Three Commercially Important Hemiramphid Species in South-eastern Australia

Synopsis

The reproductive biology of eastern sea garfish Hyporhamphus australis, eastern river garfish H. regularis ardelio, and snub-nosed garfish Arrhamphus sclerolepis were described throughout their respective ranges in the coastal waters of New South Wales (NSW), Australia. Peaks in gonadosomatic indices indicated that spawning of eastern sea garfish occurred in late spring and early summer (November–December) on the south coast of NSW, and in winter and early spring (June–September) on the north coast. Eastern river garfish spawned between July and December in NSW estuaries and snub-nosed garfish spawned between October and January in the Clarence River. The sex ratios in commercial catches of eastern sea garfish from the north coast of NSW were biased toward male fish, but approached equality for fish caught from the south coast. Sex ratios were significantly biased toward female snub-nosed garfish, and female eastern river garfish from all estuaries sampled. Mean (±SE) batch fecundity was 1498 ± 110 (range: 98 – 3449) ripe oocytes per female for eastern sea garfish, 917 ± 36 (range: 102 – 2268) ripe oocytes per female for eastern river garfish, and 716 ± 104 (range: 20 – 2956) ripe oocytes per female for snub-nosed garfish across the range of mature sizes examined. There was a linear relationship between batch fecundity and fish size for all three species of garfish. Eastern sea garfish approached 50% maturity at a larger size than snub-nosed, or eastern river garfish. Size at 50% maturity was similar for male and female eastern river and snub-nosed garfish, but male eastern sea garfish matured at a significantly smaller size than females. All three species appear capable of spawning in the spawning season immediately following the one in which they were born. Mature female fish of all three species had distributions of oocyte diameters consisting of three or four modes, which strongly suggests asynchronous oocyte development and a multiple spawning strategy during the spawning season. Implications for the management of garfish fisheries in NSW are also discussed.