Fishing For Information - The Potential for a New Abalone Fishery in South Australia

Thor Saunders, P.A.G. Preece and S. Mayfield

SARDI Aquatic Sciences, MT GAMBIER, AUSTRALIA

THEME: ASFB

Five species of abalone occur along the coastline of South Australia. Greenlip abalone (Haliotis laevigata) and blacklip abalone (H. rubra), are commercially exploited. A third species, Roe's abalone (H. roei), is also abundant and could potentially be commercially harvested. Consequently, a project involving SARDI, AIASA and PIRSA was initiated in October 2000 to investigate (1) the fisheries biology, (2) the population response to differentail fishing levels and (3) the distribution and abundance of H. roei, in the Western Zone of the South Australian abalone fishery. Tagging studies showed that H. roei grew faster at a sheltered site compared to two more exposed sites. Gonad tissue examination showed that all H. roei were sexually mature at 57 mm SL. Monthly gonad index data suffest continuous spawning. Sex ratios did not differ from a 1 male: 1 female ratio. Bimonthly size-frequency data failed to show significant temporal or modal progression trends. Commercial abalone divers harvested H. roei (MLL 75mm SL) throughout the Western Zone with an average CPUE of 35.6kg H.roei.hr. To investigate the population response to fishing, fishers harvested H. roei at 60mm SL in small defined areas. Preliminary results from a BACI experiment showed the abundance of H. roei declined significantly after fishing. Research to address all three objectives is ongoing until at least October 2003.