Publication Date

11-2007

Series Number

167

Publisher

Department of Fisheries, Western Australia

City

Perth

ISBN

1 921258 13 6

ISSN

1035 - 4549

Abstract

Final FRDC report- Project 2002/079

A digital video image (DVI) stock monitoring programme was developed for the Haliotis laevigata and H. roei abalone fisheries in Western Australia. The program used industry divers to collect stock density and length-frequency data using digital video from 51 survey sites across the fishery, while image extraction, data processing and storage is carried out by research staff. Training videos, DVDs, and a comprehensive suite of experimental tests on both abalone species were utilised to achieve this outcome. Comparisons between DVI data collected by industry divers, and fishery independent survey (FIS) data showed mean legal sized (140 mm+) density of H. laevigata to be 0.33 m-2 for the DVI method, and 0.35 m-2 for the FIS method. This difference was not statistically significant. The DVI method can also measure abundance of pre-recruits, however only samples a small proportion of juveniles. Industry and managers have recognised the potential of the DVI method, and the programme is being scaled up to provide sufficient data for on-going application to stock assessment and management.

Information on the undersized component of abalone stocks, changes in stock density, growth and habitat are not directly detectable through monitoring commercial abalone catches. To make more reliable projections on future catches of abalone, catch data needs to be supplemented with an appreciation of the strength of sub-legal year classes yet to enter the fishery. Traditionally such data is only available though fishery independent surveys (FIS), usually carried out by research personnel, and with substantial costs. However, commercial abalone divers have unequalled access to in-water stocks, and thus have the potential to provide a cost effective means of monitoring stocks within and between years over a large spatial area. To date this has been difficult to achieve because the traditional process for collecting data is considered non-independent (compromised) in the hands of commercial divers, and commercial divers perceive calliper and slate technology as slow, an undue interference and insufficient in coverage to supply representative datasets. However, advances in digital video technology have resulted in a re-appraisal of these limitations. In this project, the potential of underwater digital video imagery (DVI) obtained by commercial divers to supply useful and cost-effective data was investigated for two commercially fished abalone species in Western Australia (Haliotis laevigata and H. roei).

Number of Pages

58

Keywords

Greenlip abalone, Roe’s abalone, Haliotis sp, Digital video monitoring, Stock abundance, Length-frequency sampling, Industry divers

Disciplines

Aquaculture and Fisheries | Natural Resources and Conservation | Natural Resources Management and Policy | Sustainability

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