Tim Karlov

Physical and Behavioural Influences on the Stock Assessment of Blacklip Abalone, Haliotis rubra

Supervisors : A/Prof Malcolm Haddon (TAFI), Dr Alistair Hobday (CMAR), Prof Craig Johnson (UTAS), Dr Craig Mundy (TAFI)

Assessment of the Tasmanian blacklip abalone fishery presently relies solely upon interpretation of fishery-dependent data, particularly that relating to catch and effort . However, experience with abalone fisheries throughout the world has shown that such data represent inadequate and frequently misleading indicators of fishery performance , and reliance on such has repeatedly failed to prevent stock collapse.

Fishery-independent assessments of stock abundance can provide a more accurate indication of abundance . However, due to several factors, most notably the patchy and contagious nature of Haliotid distribution and the practical difficulties associated with dive surveys, fishery independent abundance assessments have generally proven prohibitively difficult, with low power to detect changes given available resources. This has been the case in Tasmania , where fishery independent surveys have been trialled on a number of occasions over the past 20 years without success.

This project will investigate the factors that influence the effectiveness of fishery-independent assessments of blacklip abalone in Tasmania . The work will include intensive field projects to investigate survey techniques, survey design, and abalone behaviour on several time scales relevant to the short-term recovery of fished areas and the interpretation of survey results. These data will provide the basis to develop a model to determine the effectiveness and design characteristics of a large scale abalone monitoring program independent of the fishery.