FISHING:
The effects on
the Great Barrier Reef?
Martin Russell
he Research and Monitoring Section's Effects of Fishing Program is
involved with fisheries issues relating to the Great Barrier Reef Marine
Park and World Heritage Area. The main objective of the program is to gain a
greater understanding of the impacts
of fishing to ensure ecologically sustainable fishing, the protection of critical habitats and the protection
of rare and endangered species.
The program has identified a number of critical issues affecting the Great Barrier Reef Marine Park and World Heritage Area which are being addressed through various projects. These are outlined below.
Prawn Trawling
The Effects of Prawn Trawling in the Far Northern Section
of the Great Barrier Reef Marine Park research project conducted by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Queensland Department of Primary Industries is in
its fifth and final year. The research was conducted in
and adjacent to the cross-shelf closure (Marine National Park `B' zone) in the Far Northern Section of the Great Barrier Reef Marine Park. The particular emphasis of this study was to:
- describe the fish, benthos, penaeid prawns, by-catch species and sediments of these areas and compare the communities in the cross-shelf closure area with those of adjacent areas where prawn trawling is not prohibited;
- determine the direct and indirect impacts of trawling;
- ascertain the proportion of discards (thrown overboard from trawlers) that float and sink;
- determine the fate of discards and their role in the diet of seabirds;
- identify surface and benthic scavengers; and
- estimate the rate at which individual prawn trawls deplete the benthos - this will give an assessment of the number of trawls in an area that will result in appreciable reduction in structural epi-benthos.
The release of the results for the five-year study is expected early in 1997 and will provide valuable information for the management of trawling impacts
in the Great Barrier Reef Marine Park. While it is
important to monitor the impact of trawling on seabed communities, it is necessary to determine the recovery dynamics of the seabed after trawling ceases. A project to monitor the recovery of benthos, using underwater video is being conducted by the CSIRO. The recovery relates to benthos in the trawl tracks that were repeatedly trawled in the final year of the research project mentioned above. Preliminary results are expected in mid-1997, from which future monitoring requirements will be determined.
Reef-Line Fishing
The Great Barrier Reef supports a widespread commercial reef-line fishery which is of great economic and social importance to the people of Queensland. The fishery is multi-specific, with most fishers targeting around 10-20 species of the coral reef fish found on the Great Barrier Reef. The major species targeted by the fishery is Plectropomus leopardus (common coral trout).
Bramble Reef, in the Central Section of the Great Barrier Reef Marine Park, was closed to fishing in 1992 by the Great Barrier Reef Marine Park Authority due to community concern that the reef fish stocks had been overfished and needed replenishment. A monitoring program was set up prior to the closure to monitor changes in commercially important fish stocks (namely coral trout and red-throat emperor), other reef fish
species and coral cover on Bramble Reef relative to
similar control reefs, before and during the closure
and after the 1995 re-opening. Researchers from Sea Research are providing valuable long-term data sets on the state of the reef fish stocks for Bramble Reef during the closure and re-opening. The Cooperative Research Centre for Ecologically Sustainable Development of the Great Barrier Reef (CRC Reef Research Centre) conducted commercial and recreational fishing surveys to monitor fishing activity, fishing catch and effort, and changes in size and age structure of target species on Bramble Reef during the re-opening in 1995. A comprehensive analysis of the surveys is due mid-1997.
An experiment proposed by the CRC Reef Research Centre will involve research in `Fisheries Experimental Areas' in the Great Barrier Reef Marine Park. The experiment on selected reefs subjected to different zoning regulations, will quantify the impacts of reef-line fishing and determine the environmental effects of reef-line fishing on targeted fish species and reef communities. The results will be of immediate benefit to all sectors of
the fishery and management agencies, and will help maintain fish stocks and sustainable fishing on the Great Barrier Reef in the long term.
The CRC study will provide:
- a reliable estimate of the relative size and status
of target fish populations on individual open and
closed reefs;
- information on the impact that increased fishing pressure has on target fish populations, other reef species, and the potential for future fishing;
- information on the levels of fishing effort that can be sustained in the long term;
- information on the methods that should be used
to monitor the status of fish populations and the
fishery and signals from those methods that would
indicate developing problems that require direct
management action;
- information on what catch rates of coral trout
mean in terms of relative abundance of coral trout on a reef;
- information on how quickly coral trout populations and catch rates recover following closure to fishing;
- testing of management options for the fishery; and
- effective adoption of different management strategies designed to conserve fish stocks on the Great Barrier Reef.
For the research to be conducted, amendments need
to be made to existing Great Barrier Reef Marine Park zoning plans by the Great Barrier Reef Marine Park Authority so that Fisheries Experimental Areas
can be established for a total of four groups of six
reefs in the Cairns, Central and Mackay/Capricorn Sections of the Marine Park. The experimental design
was considered by the Senate and the zoning plan amendments were passed through Federal Parliament late December 1996. The Authority has designated
the first of the fisheries experimental provisions
that will apply to four individual Fisheries
Experimental Areas (reefs) from 29 March 1997.
These four reefs are designated to be opened to fishing for one year. After the one year opening, the four
reefs will then be re-closed. The provisions were
made by way of a written advertisement, which
appeared in local and state newspapers and in the Commonwealth Gazette. The completion of these processes will then allow the research experiment to begin. After the one year opening of these four reefs
an additional four reefs that are currently open to
fishing are proposed to be closed to fishing for a period of five years.
Fish Spawning Sites
Currently staff within the Effects of Fishing Program
are compiling information on spawning aggregations
of coral trout (Plectropomus spp.), red-throat emperor (Lethrinus miniatus) and maori wrasse (Cheilinus undulatus). These spawning aggregations are possibly targeted by the commercial reef-line fishery on the
Great Barrier Reef. Spatial and temporal information
on spawning for these species is necessary to ensure
key spawning sites and seasons are not disturbed or impacted by tourism or fishing.
Mesh-netting and Dugongs
Surveys have detected a dugong population decline in the southern region of the World Heritage Area (south of Cooktown) of between 50-80% over the past eight years, and a patchy decline in the northern region of the World Heritage Area. Research indicates that the population in the southern region can only cope with a loss of less than 1-2% (females) each year. Of the dugong deaths in the Great Barrier Reef World Heritage Area reported to the Great Barrier Reef Marine Park Authority in 1996, 37.5% are confirmed to have been caused by mesh-nets. Based on this evidence the continuing mortality of dugongs in mesh-nets is not sustainable and therefore of great concern to the Authority. Management strategies for mesh-netting in the Great Barrier Reef World Heritage Area are being developed in conjunction with industry and stakeholders with a view to eliminating the risk of mesh-nets to
dugong survival. Urgent action is required and a number of options for joint Commonwealth and Queensland emergency measures are being considered to arrest the apparent rapid decline. Data acquisition, analysis and reporting on dugongs and mesh-netting are required. This includes fine scale surveys of dugong distribution and habitat, a bather protection net review, information on the types of mesh-nets used and where the nets are being used in the Great Barrier Reef World Heritage Area, seagrass diseases incidence and implications for dugong, vessel use of dugong habitat, and indigenous hunting. The Great Barrier Reef Marine Park Authority, in cooperation with the Queensland Department of Environment, the Queensland Fisheries Management Authority, the Queensland Commercial Fishermen's Organisation and the Queensland Department of Primary Industries, is to report to the Commonwealth and Queensland Governments by the end of February 1997 on what action is required to ensure that no further dugong mortality occurs as a result of commercial and recreational fishing practices in Interim Dugong Protection Areas.
Trawl Efficiency Devices / Turtle Exclusion Devices (TEDs)
There is increasing concern about the incidental capture of marine animals by prawn trawlers in Australian waters. Current research and management strategies are attempting to address the concern through strategies such as the introduction of Trawl Efficiency Devices (TEDs) (also known as Turtle Exclusion Devices). There is a need for the introduction of TEDs to reduce the incidental capture of sea turtles by prawn trawling in Australian waters. Industry has shown a positive role in the development of TEDs, by taking part in research trials. The introduction of TEDs into the Great Barrier Reef World Heritage Area will provide potential benefits to the industry and the environment by increasing fishing efficiency and considerably reducing sea-turtle mortality. Through a cooperative approach with industry, and the provision of technical support from State and Federal agencies, the implementation and further development of a variety of TED designs to cope with varying conditions and by-catch in the Great Barrier Reef World Heritage Area will be achieved.
Great Barrier Reef Lagoonal Benthic Communities
Little is known of the structure of benthic communities in inter-reefal and lagoonal areas of the Great Barrier Reef Marine Park. To set the results from the Effects of Prawn Trawling in the Far Northern Section of the Great Barrier Reef Marine Park project in the context of the whole Great Barrier Reef, a much better description of the benthic communities throughout the Great Barrier Reef is required. The Effects of Fishing Program proposes to compile existing information to develop a broad scale map for inter-reefal and lagoonal benthic communities and where information gaps occur.
The potential impact of fishing activity, both directly on targeted species and indirectly on associated ecosystems, in the Great Barrier Reef World Heritage Area is the primary concern to the Effects of Fishing Program. By addressing the critical issues mentioned above and by collaborating with fisheries
management agencies to integrate fisheries and ecosystem management,
we hope to ensure that fishing
in the Great Barrier Reef World Heritage Area is sustainable and that habitats and rare and endangered species are protected.
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Great Barrier Reef Marine Park Authority
PO Box 1379 TOWNSVILLE QLD 4810. Phone: (077) 500 700, Fax: (077) 726 093
E-mail: registry@gbrmpa.gov.au