Project number: 2003-050
Project Status:
Completed
Budget expenditure: $98,181.99
Principal Investigator: Alan Jordan
Organisation: University of Tasmania (UTAS)
Project start/end date: 12 Jul 2003 - 30 Jun 2006
Contact:
FRDC
TAGS
Survey
Remote Sensing
Habitat
Fisheries Management
Ecosystem

Need

The need for strategic R&D in the mapping of coastal seabed habitats supporting fisheries and linking fisheries assessments with such mapping has been identified through several Commonwealth (FRDC - 95/055, 98/223 94/040 and 94/037) and in the Tasmanian Marine Environment Strategic Research Plan (1999-2004.

These needs are reflected in this proposal that aims to provide spatial information on abalone habitats in several key fishing blocks relevant to both site specific fishery independent abundance surveys and stock assessments at the block scale.

The need for fishery independent abundance surveys and assessment of physical and species interactions for abalone in Tasmania are high priority issues in the Tasmanian Abalone Strategic Research Plan and a review of abalone research needs (FRDC project 98/170). This is reflected in the current abalone FRDC project (2001/074) and ongoing abalone abundance surveys. The project proposed here will significantly contribute to this research by providing fine-scale maps of the biological and physical structure of abalone habitats which will help to optimise abalone abundance and population studies by having better criteria on which to select survey sites. It will also further improve abalone assessments by providing estimates of reef habitat for several key blocks and assisting in the correlation of environmental and habitat variables on catch rates and population parameters. In particular, there is a need to examine the structure of reef habitats in north-east Tasmania where many areas have become ‘unproductive’ for abalone in recent years and there are considerable urchin barrens present, the of which is required through detailed mapping.

In addition, further R&D is needed in the area of cost-effective acoustic and video assessment techniques. This project aims to advance this R&D and continue the transfer of technology to other agencies that TAFI has been progressing. The increase in coastal mapping in Australia also requires a framework and consistency for classifying habitats at a range of hierarchical scales. This is being progressed in the FRDC project 2002/097 ‘Development of national habitat classification framework’, which will require a significant input from mapping projects such as proposed here for the classification scheme to be comprehensive and representative.

Objectives

1. To map the fine-scale (1:5,000) biological and physical structure of rocky reef habitats in south-east and north-east Tasmania abalone fishing blocks
2. To contribute to the survey design and outcomes of the FRDC abalone project (2001/074) and ongoing abalone assessment by linking information on reef and macroalgal extent and structure to abundance and population parameter assessments
3. To further develop cost-effective techniques for fine-scale habitat mapping and classification

Final report

ISBN: 1-86295-265-5
Author: Alan Jordan
Final Report • 2005-12-08
2003-050-DLD.pdf

Summary

The Tasmanian commercial fishery for blacklip abalone (Haliotis rubra) and greenlip abalone (H. laevigata) contributes a significant component of the total Australian abalone catch, with annual landings of around 2590 tonnes in 2003.  The catch consists primarily of blacklip abalone (around 95%) which is taken throughout the State, with the greenlip catch restricted to the north coast and Bass Strait islands.  The catch of blacklip abalone is not evenly distributed around the State reflecting a range of issues including stock abundance, fishing area accessibility and market preference for particular sized animals. 
 
Spatial management of the fishery occurs at three levels of geographic zones (Eastern, Western and Northern), fishing blocks and fishing sub-blocks.  The south-east region of Tasmania between southern Southport Lagoon and Whale Head, which makes up a large proportion of block 13 (sub-blocks C-E) consists of extensive reef habitat that supports annual blacklip abalone commercial landings averaging at around 395 tonnes over the past decade.  This represents around 10% of the statewide catch despite representing only 0.8% of the Tasmanian coastline indicating the highly productive nature of this area.  In contrast, the north-east fishing blocks 30 and 31 represent around 3% of the coastline but over the past decade have had annual average landings of only 33 tonnes (which in block 31 consists of a small proportion of greenlip abalone).  While recent landings have been small, the region supported significant blacklip abalone catches during the 1980’s (with a peak of 300 tonnes in block 30 in 1983 and 225 tonnes in block 31 in 1985).  There is evidence that this was driven by this high fishing effort in the 1980s resulting in considerable serial depletion of reefs, which combined with poor recruitment has resulted in many reefs in this region becoming ‘unproductive’ in terms of abalone stocks.
 
The primary objective of this study was to map seabed habitats in abalone fishing blocks in north-east (blocks 30, 31) and south-east (sub-blocks 13C-E) Tasmania in order to better understand the extent, distribution and structure of rocky reef habitats within these regions.  Such information was seen as an important component of the overall research required to improve the long-term sustainable management of abalone fishing in these blocks.  The reefs were mapped at a number of scales in order to determine the overall amount of reef, spatial patterns of reef systems, fine-scale (~1-10 m) structuring (i.e. profile, proportion of sand), patterns of macroalgal assemblages and extent of urchin barrens.

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