Linking habitat mapping with fisheries assessment in key commercial fishing grounds

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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Environment

Designing, implementing and assessing an integrated monitoring program for the NPF: developing an application to stock assessment

Project number: 2003-075
Project Status:
Completed
Budget expenditure: $570,080.00
Principal Investigator: Yimin Ye
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 30 Aug 2003 - 30 Sep 2005
Contact:
FRDC
TAGS
Survey
Stock Assessment
Reproduction
Population Dynamics
Fishing Gear
SPECIES
King Prawns
Banana Prawns
Tiger Prawns
Endeavour Prawns

Need

An international review of the NPF tiger prawn assessment agreed with the conclusions of the 2001 assessment that tiger prawn levels are critically low, especially for brown tiger prawns. The 2002 assessment has further concluded that brown tiger prawn levels are too low but has also emphasized the critical need for an independent monitoring program given the confounding and complexities of the catch rate data used as the sole index of abundance in the NPF assessments.

The survey data used to determine the initial design for this project (see Background) is more than a decade old and does not cover the full study area. Therefore the initial surveys will be largely exploratory in nature and very much a trial to see if the proposed design is effective. Also, the survey design includes integrated components such as the assessment of long-term changes in fishing power and the contraction of the fishery over time that have not been undertaken in prawn survey designs (both nationally and internationally) before. These aspects highlight that this project has a large research component; the appropriate survey design is still being developed and methods for incorporating the results of the surveys into future stock assessments need to be developed.

In this proposal, the CSIRO salaries associated with modifying the survey design and with developing new methods of incorporating the results into stock assessments are seen as research. We are therefore requesting about $60,000 from FRDC’s MOU funds. For this reason, CSIRO is also supporting the project to the scale of about $87,000. The remainder of the project, some $510,000, will be underwriten by the industry as agreed in NORMAC, June 2003. The industry and NORMAC have also re-affirmed the long-term need for regular industry-funded monitoring surveys based on the output of this project.

There is a need to provide an updated design for the NPF that would work in the long-term to provide indices of abundance to key species and enhance a difficult-to-use commercial catch rate series. Furthermore, this design needs to address target, byproduct and possibly some effects-of-trawling issues to make the best use of the surveys, as they will be a large expense to the industry.

Objectives

1. To determine the final design and analyses for two surveys in the Gulf of Carpentaria
2. To undertake a survey in August 2003 to provide biomass and spawning indices of the main commercial prawn species in the Gulf of Carpentaria
3. To undertake a survey in January/February 2004 that will provide a recruitment index of the main commercial prawn species in the Gulf of Carpentaria
4. To determine the appropriate scale and frequency of future surveys
5. To spatially map the distribution of the main prawn and byproduct species in the Gulf of Carpentaria

Final report

ISBN: 1-876-996-81-1
Author: Yimin Ye
Final Report • 2005-09-08
2003-075-DLD.pdf

Summary

For more than a decade the Northern Prawn Fishery assessments have indicated that the tiger prawn resource is overexploited. Deriso’s1 (2001) review of the tiger prawn assessment supported this conclusion and also drew attention to the high level of uncertainty in the assessment. Deriso strongly recommended that the logbook data be augmented by fishery-independent survey data and that the survey should be designed both to provide an independent index of abundance for each tiger prawn species and to quantify fishing power changes. The clear message of the review was that a survey program is an essential investment for this fishery.
 
In response to this review, an initial industry-funded (Dichmont et al. 2002) consultancy was established to investigate and design an integrated monitoring program for the NPF.  The initial design results were presented to a well-attended industry meeting in Cairns in February 2002.  Suggestions from industry were incorporated into the project and a final report included a modular design and costing structure, which was presented to a special NORMAC meeting in March 2002.  This meeting agreed to all components of the proposed program except the work in Joseph Bonaparte Gulf, which was seen as premature. As a result of this decision, a one year pilot test of the desk top design was undertaken incorporating two trawl surveys in 2002/03 (Dichmont et al. 2003). The first, aimed at estimating a spawning index that could also be used in future fishing power studies, was undertaken in 3 regions of the Gulf of Carpentaria (GOC) in August 2002. The second survey aimed to produce an index of recruitment and was undertaken throughout most of the fishing regions of the Gulf of Carpentaria in January/February 2003.  The final funding mix, based on an assumption of a 50:50 ratio of monitoring to research, was 50% industry funded and the remainder equally funded by AFMA Research Fund, FRDC and CSIRO.
 
The current project (FRDC 2003/075) aims to continue the surveys, finalize the design and develop techniques that can effectively use the survey data to improve stock assessment.