Marine Disturbance in Parts of the Australian Exclusive Economic Zone

Australia: State of the Environment Second Technical Paper Series (Coasts and Oceans), Series 2
David Barratt, John Garvey and Jean Chesson
Bureau of Resource Sciences, Australia
Department of the Environment and Heritage, 2001
ISBN 0 6425 4745 9

Executive Summary

Australia's National Strategy for Ecologically Sustainable Development calls for the introduction of regular state of the environment reporting at the national level to enhance the quality, accessibility and relevance of data relating to ecologically sustainable development.

The first major product of this reporting system was Australia: State of the Environment 1996 (State of the Environment Advisory Council 1996) - an independent, nation-wide assessment of the status of Australia's environment. The next national state of environment report is due in 2001. In order to assess changes in the environment over time it is necessary to have indicators against which performance may be reviewed. To help develop these indicators, Environment Australia commissioned reports recommending indicators for each of the seven major themes around which Commonwealth state of environment reporting is based. From these reports Environment Australia has selected the most practical and cost effective indicators for further implementation. The four indicators covered by this project were derived from the reports on estuaries and the sea (Ward et al., 1998) and biodiversity (Saunders et al., 1998).

The indicators are:

Total of fishing bycatch (ie non-target species, discards, incidentals, etc) relative to catch of target species
The number of fisheries management plans that have effective indicators for monitoring the level of, and the extent of reduction in, impacts on non-target organisms and their habitats (where applicable)
The extent of fishing conducted by longline, dropline, gillnet and meshing operations
The area of sea and seabed subject to (a) demersal trawling, (b) other trawling, (c) exploration and (d) mining.

The project involved seven tasks:

Review existing information
Document relevant data sources
Assemble relevant data
Assess the quality of available data
Present the data in a specified form
Clarify details of indicators as required
Assess and evaluate any real or apparent trends in the data and comment on their environmental significance.

Tasks 1 and 2 were applied nationally to all indicators. Tasks 3 to 7 were applied nationally to Indicator 2 and to the petroleum-related aspects of Indicator 4. For the remaining indicators, Tasks 3 to 7 were restricted to case studies of selected fisheries or areas.

The seven case studies (two for Indicator 1, three for Indicator 3 and two for Indicator 4) focussed on the waters off NSW and Victoria because of the diversity of activities in this area and because this is the first area for which a Regional Marine Plan will be developed under Australia's Oceans Policy.

Methods used included the compilation of a comprehensive list of Australian fisheries and the type of fishing methods they use (a significant achievement which has already had multiple uses); an analysis of data collection forms used in logbooks and fisheries returns throughout Australia; examination of all available fisheries management plans and telephone interviews with representatives of all fisheries management agencies. Data sources for petroleum and minerals exploration and extraction were documented. Work on minerals exploration and extraction was restricted to reviewing and documenting mining activities in the States and Territories. Spatial and temporal data were assembled for petroleum exploration and extraction.

GIS analyses were applied to spatial data for Indicators 3 and 4. Data that met minimum quality criteria were used to map the relative intensity of fishing effort and petroleum exploration effort by grid and by IMCRA region. Methods were developed to handle trawl and seismic survey track records. Approaches to mapping 'change over time' were explored and a simple option was adopted. Further investigations are planned.

The results are presented in over 30 maps as well as numerous charts and tables. Map presentations were standardised across fisheries and land area that would otherwise be blank was used to display relevant charts.

The conclusions and recommendations of the project are reproduced in the box below.

Conclusions and Recommendations

General

There are at least two different approaches to developing national indicators. The first approach adds or otherwise combines information from each contributing unit (for example, a fishery). To do this, data need to be compatible across units and impacts are assumed additive. The significance of the value of the indicator is then determined against some national objective. In the second approach, data are collected and their significance assessed against an objective specified at the level of the unit. The national indicator is then expressed in the form 'number or proportion of units meeting their individual objectives'. In the second approach, the type of information collected may differ among units.

We suggest that Approach 1 can be used for indicator 1 (bycatch) if the indicator is defined in terms of total removals. The basic data is or should be collected for every fishery. However, once attention moves to more detailed issues such as individual species, the approach should shift to Approach 2 where data collection and interpretation is specific to the circumstances of the individual fishery.
Indicator 2 (management plans) uses Approach 2 by definition.
It is possible to use Approach 1 with Indicators 3 and 4. However, some sub-indicators involving fishing effort need to be broken down further by gear type to allow sensible summation of data. Even then, the problem remains that the same effort value may represent a quite different pressure in different ecosystems. We suggest that Approach 2 may prove to be a more fruitful approach in many cases.

More work is required in the area of data validation and error checking. A formal, repeatable and, as much as possible, automated process of validating data and resolving spatial and other errors as data enters a management authority system is urgently needed.
Confidentiality of fisheries logbook data requires more discussion in political, legal and scientific contexts. Indicators describing the area and intensity of fishing and trawling immediately come into conflict with the issue of confidentiality of logbook data. The States and the Commonwealth have policies of not allowing the public reporting of logbook data, unless those data are aggregated by a certain number of vessels or fishers. However, in many fisheries, a small number of boats in an area does not necessarily mean a low level of fishing effort, either absolutely, or relative to other parts of the fishery

Indicator 1: Bycatch

Based on the fishing methods involved, it is estimated that 114 (79%) of Australia's 144 commercial fisheries have low to very low discard rates (less than 25% of the total catch discarded). There are 19 fisheries with moderate discard rates (25 to 50% of total catch discarded) and 11 fisheries with high discard rates (greater than 50% discarded).
The South-East Fishery is one of the few examples where bycatch information is available over time. Between 1994 and 1997, the amount of discarded catch was variable but showed no obvious trend.
'Bycatch' is an ambiguous term. The indicator needs to be more clearly defined to specify precisely which bycatch issue it is attempting to address.

Based on our investigation of this indicator, we recommend that:

Environment Australia pursue the total removal indicator as listed in the ANZECC core indicator set, but only as an aggregate across species. We recommend against catch (retained, discarded or total) as an indicator of either state of, or pressure on individual species because catch is just one of a number of pieces of information that are needed to make such an assessment.

Indicator 2: Fishery management plans

There are 144 managed marine and estuarine fisheries in Australia of which 60 have management plans. Of the 27 management plans which were available for analysis, 5 plans have indicators for monitoring non-target species. Western Australia's 33 management plans were unavailable and were not analysed, however WA Fisheries management staff reported only one plan contained references to non-target species.
This indicator is relatively easy to implement, but it needs to be clarified if it is to provide a useful measure of the anticipated increase in monitoring of fishery impacts on non-target species. 'Management plan' has to be interpreted in a generic sense to refer to any publicly stated plan, not just the formal management plan referred to in the legislation of many jurisdictions. Since more than one document may be involved, the indicator should be expressed in terms of fisheries rather than management plans.
Measuring the effectiveness of non-target species monitoring indicators within management plans is more problematical. At present there is little to guide fisheries managers in the selection of effective indicators for non-target species. This is an active research area.

Based on our investigation of this indicator we recommend that:

The indicator is reworded to read 'The number of fisheries with publicly available plans that have effective indicators . . etc.'
The work carried out in this project should be repeated before the 2006 State of the Environment Report to document the expected increase in monitoring of impacts on non-target species.
Fisheries management authorities should implement a system of 'metadata' recording for their fisheries, where all the documents relevant to each fishery are identified at a single access point.

Indicator 3: Line and net fishing

Core fishing areas within line and net fisheries are generally small relative to the total area of a fishery. Consequently, areas of relatively high fishing intensity tend to be very small relative to the total area of a fishery. IMCRA regions are inappropriate analytical units for spatial and temporal analyses of the Southern Demersal Longline and Southern Dropline fisheries because of the significant amounts of fishing occurring beyond the continental shelf.
The Australian Pelagic Longline fishery is increasing in both area and intensity of fishing. The intensity of Danish seining in the South East Fishery is also increasing. The geographic extent of Danish seining appears to have shifted south and west over the last decade, though the total area of the fishery is relatively stable. The case studies examined indicate the Twofold Shelf region may be the most highly disturbed of the IMCRA regions in south-eastern Australia with respect to disturbance indicator 3.
It is not currently possible to report on the spatial extent and intensity of net and line fishing on a national scale. This is because less than half of the logbooks and forms identified as data sources for indicator 3 met the spatial, temporal and effort data quality criteria developed to filter information for analysing and mapping the indicator. Also, this indicator currently comprises both hook and net fishing methods and consequently can only be reported on by using the number of fishing operations as a surrogate for fishing effort.
The spatial analysis of temporal trends in the area and intensity of fishing operations is currently confounded by changes in the spatial precision of logbook data over time.

Based on our investigation of this indicator we recommend that:

The indicator should be split into the seven indicators listed under the recommendations in the indicator chapter.
Management bodies should be encouraged to improve the accuracy and precision of information being received from fishing vessels. Logbooks should collect, as a minimum, the data listed under the recommendations in the indicator chapter.
Work on further sub-regionalisation of the current IMCRA regions and incorporation of the waters above the continental slope is required. The impact of fishing on marine species and communities in the Twofold Shelf IMCRA region should be examined as a priority.

Indicator 4: Trawling, exploration and extraction

The data from the South East Trawl fishery and from petroleum exploration and extraction operations indicate the Twofold Shelf region may be the most highly disturbed of the IMCRA regions in south-eastern Australia with respect to indicator 4. However, IMCRA regions are inappropriate analytical units for spatial and temporal analyses of the South East Trawl fishery because significant amounts of trawling occur beyond the continental shelf.
The intensity of trawling in the South East Trawl fishery is increasing. Trawling intensity and area in the Northern Prawn Trawl fishery have decreased substantially in the last decade, but currently appear to be slowly increasing. Core fishing areas in trawl fisheries are generally small relative to the total area of a fishery. Consequently, areas of relatively high trawling intensity tend to be very small relative to the total area of a fishery.
It is currently possible to calculate the area of seabed swept by trawl gear to spatially represent trawl effort for indicator 4(a), contingent on certain explicit assumptions. However, the coarse spatial resolution of some logbook data is a limiting factor, with only 13 of the 18 logbooks and forms identified as data sources for the indicator meeting the spatial data quality criteria that were developed to map the indicator.
The spatial analysis of temporal trends in the area and intensity of trawling operations is currently confounded by changes in the spatial precision of logbook data over time.
Levels of hydrocarbon exploration and production activity have fluctuated markedly from year to year, but overall there has been a small increase in both types of activity since the early 1990s, particularly in terms of the length, if not number, of survey tracks and wells.
Petroleum industry activities and facilities occupy only a very small surface area of the sea bed and, in the case of exploration activities, are of short-term duration. They are concentrated almost entirely in the region of the Gippsland Shelf (Twofold Shelf IMCRA region), although recently new fields have been discovered and opened up for exploration on the Carnarvon Shelf off northwest Australia.
The number of approval instruments or size of areas held under petroleum title are not useful indicators of the pressure on ecosystems because the type and level of activity can vary considerably within these areas.

Whilst there is some potential to use the extent and intensity of seismic survey activities as an indicator of marine disturbance, a clearer understanding of their impacts awaits the outcome of current research activities.
The number and location of active and recent drilling wells can be used with some confidence to infer the extent of impacts on benthic flora and fauna.

Based on our investigation of this indicator, we recommend that:

The indicator should be split into the four indicators listed under the recommendations in the indicator chapter.
Management bodies should be encouraged to improve the accuracy and precision of information being received from fishing vessels. Logbooks should collect, as a minimum, the data listed under the recommendations in the indicator chapter.
Further research is necessary to improve and quantify our understanding of the relationship between seismic surveying and impacts on marine organisms if exploration effort is to be used as a surrogate of marine disturbance.
Work on further sub-regionalisation of the current IMCRA regions and incorporation of the waters above the continental slope is required.The impact of trawling and mining on marine species and communities in the Twofold Shelf IMCRA region should be examined as a priority.