Effects of Trawling Subprogram: mapping bycatch & seabed benthos assemblages in the GBR region for environmental risk assessment & sustainable management of the Queensland east coast trawl fishery

Project number: 2003-021
Project Status:
Completed
Budget expenditure: $918,237.00
Principal Investigator: Roland C. Pitcher
Organisation: CSIRO Oceans and Atmosphere Crawley
Project start/end date: 18 May 2003 - 28 Feb 2008
Contact:
FRDC
TAGS
Sustainability
Survey
Oceanography
Habitat
Fishing Gear

Need

The CSIRO/QDPI Effects of Trawling Study¹ concluded that if the substantial cumulative environmental effects of trawling are to be managed for sustainability then fundamental information on the distribution and abundance of seabed assemblages and bycatch is essential. The “Management Scenario Model” for the QECTF has indicated that potential sustainability indicators for Management Strategies Evaluations (MSE) are highly sensitive to current assumptions about the distribution and abundance of species vulnerable to trawling. This proposal addresses this important information gap and impediment to management for environmental sustainability by conducting an inventory and mapping of species caught in bycatch and seabed assemblages throughout the GBR region, for development of sustainability risk indicators and MSE approaches.

Bycatch is a priority issue in the QECTF. This proposal addresses the information needs of this issue in two ways: (1) developing bycatch sustainability risk indicators and (2) quantification of the impacts on populations of bycatch species. To address (1), the project will map the distribution and abundance of species caught in bycatch, within and beyond trawl grounds, and estimate the proportion of their populations exposed to trawling by conducting spatial analyses of bycatch species abundance in relation to trawl effort distribution and intensity. (2) will develop this analysis further, using available data on the catch-rate of bycatch species by the fishery, to estimate the proportion of bycatch populations caught annually, as a risk indicator. The Project will also apply the bycatch vulnerability criteria for life history traits (recovery) that have been developed by the successful NPF Bycatch sustainability Project (FRDC 96/257 — see Methods for details) and are now playing a key role in the NPF Bycatch Action Plan. Together, this information can be use to identify those species likely to be at risk in the QECTF and will deliver directly to the bycatch reporting requirements for Strategic Assessment and subsequent accreditation outcomes. Similar information and outcomes are likely to be available for several target & by-product species, as well as some threatened or potentially threatened species such as pipe-horses.

The direct impacts of trawling on seabed benthic assemblages are also a priority issue in the QECTF. This project will address the information needs of this issue by mapping the distributions of seabed assemblages, conducting spatial analyses and developing benthos sustainability indicators similar to that for the bycatch. This will be done by applying the vulnerability algorithms developed for the CSIRO/QDPI Effects of Trawling Study FRDC 93/096 (ie. the dynamics of per trawl removal rate × trawl-effort, plus recovery rate information from the GBRMPA follow-on project Seabed Habitat Recovery Dynamics, as well as the FRDC 97/205 Megabenthos Dynamics Project — see Methods for details). This information will enable development of benthos status indicators and evaluation of the environmental performance of different management scenarios (MSE) that may be adopted by the fishery management. Again, these outputs will deliver directly to the reporting requirements for Strategic Assessment and subsequent accreditation outcomes.

The Managers and Industry consider that the project is essential for the requirement to provide a comprehensive assessment of the sustainability of the fishery. Information from this project will assist the stakeholders with their management of the fishery, assessment of performance against Trawl Management Plan targets (40% reduction in bycatch & 25% reduction in benthos), response to Strategic Assessment and meeting requirements of the EPBC Act, conduct of ecological risk assessments and development of biologically meaningful reference points (required by 2006), evaluation of the zoning changes in the GBRMP, and review of the Trawl Management Plan (2004-06) — and reaching the goal of achieving a sustainable fishery. The Project will deliver results progressively, so that timely outputs will be available for these review processes.

A related current & important issue that this Project will deliver to is the sustainability of the Reef Line Fishery, which is currently subject to a proposal for capping at 1996 levels and spawning season closures. One of the greatest uncertainties regarding the sustainability of this Fishery is the unknown area of deeper inter-reef habitat and the populations of demersal fishes therein — this proposed Project will be able to provide estimates for both of these uncertainties and so enable the EoLF Projects to capitalise on this information and value-add to the investments of FRDC and other agencies in EoLF research.

The Project will also deliver relevant priority research needs relevant to the development of national habitat classification and mapping methods, as identified at the FRDC/NOO Habitat Workshop, 23-24 September 2002.

Objectives

1. The overall objective is to address key R&D priorities identified by the Qld TRAWLMAC, QFIRAC, QFS, GBRMPA and the FRDC Effects of Trawling Sub-Program in relation to environmental sustainability assessments of the Qld East Coast Trawl Fishery with respect to effects on bycatch and seabed benthic assemblages, and support ecologically-based management of the fishery, achieve environmental sustainability, Strategic Assessment and accreditation. Specifically:
2. Develop & provide maps of the distribution of seabed assemblages to managers and stakeholders, with the outcome of management strategies effective in minimising fishery effects on seabed habitats & assemblages, and achievement of Management Plan targets.
3. For both bycatch & benthos, develop quantitative indicators of exposure to & effects of trawling, and sustainability risk indicators, as required for the environmental Strategic Assessment of the QECTF.
4. Provide critical input to a dynamic model of indicators for the status of seabed assemblages and conduct ecological assessments of recent and proposed management changes using an MSE approach, and enable capability for evaluation of future options.
5. Contribute to quantifying the large-scale effects of trawling on bycatch species and benthos assemblages by analysing their abundance across the range of trawl intensities within and outside trawl grounds, while accounting for habitat variability.
6. Develop transferable scientific methods and tools to facilitate regional marine management planning nationally, including: knowledge of bio-physical relationships between assemblages and the physical environment (surrogates), cost-effective survey designs & techniques (including performance of rapid assessment tools: video & acoustics), spatial-statistical classification & prediction methods, and sustainability risk indicators for seabed species, assemblages and communities.
7. Complete a sixth 35 day field sampling voyage on the AIMS research vessel (Lady Basten) to fill critical gaps remaining in the southern GBR.
8. Complete a fourth 35 day field sampling voyage on the QDPI&F fisheries research vessel (Gwendoline May) to fill critical gaps remaining in the southern GBR.
9. Produce maps of habitats and biodiversity values to assist Commonwealth and State managers of the GBR Marine Park to recognise and conserve marine biodiversity consistent with CAR principles, and assist managers of Queensland's fisheries to ensure that trawling in the WHA is consistent with ESD principles.

Final report

ISBN: 978-1-921232-87-9
Author: Roland Pitcher
Final Report • 2009-02-26 • 22.80 MB
2003-021-DLD.pdf

Summary

The Great Barrier Reef is a unique World Heritage Area of national and international significance. As a multiple use Marine Park, activities such as fishing and tourism occur along with conservation goals. Managers need information on habitats and biodiversity distribution and risks to ensure these activities are conducted sustainably. However, while the coral reefs have been relatively well studied, less was known about the deeper seabed in the region. From 2003 to 2006, the GBR Seabed Biodiversity Project has mapped habitats and their associated biodiversity across the length and breadth of the 210,000 km² shelf in the Marine Park to provide information that will help managers with conservation planning and to assess whether fisheries are ecologically sustainable, as required by environmental protection legislation (e.g. EPBC Act 1999).
 
Holistic information on the biodiversity of the seabed was acquired by visiting almost 1,400 sites, representing a full range of known environments, during 10 month-long voyages on two vessels and deploying several types of devices such as: towed video and digital cameras, baited remote underwater video stations (BRUVS), a digital echo-sounder, an epibenthic sled and a research trawl to collect samples for more detailed data about plants, invertebrates and fishes on the seabed. Data were collected and processed from >600 km of towed video and almost 100,000 photos, 1150 BRUVS videos, ~140 GB of digital echograms, and from sorting and identification of ~14,000 benthic samples, ~4,000 seabed fish samples, and ~1,200 sediment samples.
 
The project has analysed this information and produced all of the outputs as originally proposed.

Related research

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Environment

Evaluating the recreational marron fishery against environmental change and human interactions

Project number: 2003-027
Project Status:
Completed
Budget expenditure: $315,953.00
Principal Investigator: Martin de Graaf
Organisation: Department of Primary Industries and Regional Development (DPIRD) WA
Project start/end date: 29 Jun 2003 - 29 Aug 2008
Contact:
FRDC
TAGS
Survey
Stock Assessment
Reproduction
Recreational Fishing
Nutrition
SPECIES
Marron

Need

Both the catch and range of marron have reduced over the last 25 years. A re-evaluation of the range will provide both the current extent and potential of the recreational marron fishery (RMF) and allow a re-interpretation of current production of the RMF.

Selecting two indicator sites will allow the focusing of research effort to achieve a new, useful level of detail on fecundity, recruitment and survival in indicator stocks, develop new performance measures and new models of productivity (stock recruitment and yield-per-recruit models). Although focused on indicator stocks, this will produce generic tools applicable to other marron stocks, providing a suite of powerful management indicators.

Changes in legal gears have occurred and these gears are likely to have different efficiencies and may explain a proportion of the decline in marron catches. By quantifying the relative efficiencies of the three legal gears, the historical data set can be re-evaluated to allocate a proportion of the decline in catches to changes in gears and predictions of the impact of future gear restrictions.

Identifying and ranking sources of marron mortality will provide key information on marron survival at various life-stages and allow management to focus resources on important mortality sources.

Environmental variables and management of catchments and water resources profoundly influence the extent and productivity of the entire RMF. The collection of data and development of models will provide fishery managers to identify key influences and engage with other management agencies to promote a more sustainable and productive RMF.

Objectives

1. To assess the present range of the recreational marron fishery (RMF) and compare to the historical range to quantify the reduction in marron range and current extent of the fishery.
2. To assess fecundity, recruitment and survival of marron in indicator sites to develop performance measures and models of productivity.
3. To quantify the relative efficiency of the three permitted capture methods at indicator sites and use the results to standardise the historical catch and effort database.
4. To identify and rank sources of mortality of marron at indicator sites.
5. To model the impact and effect of key environmental variables on marron stocks within the indicator sites and the RMF as part of the overall understanding of the decline in the fishery.
6. Piloting the qualitative assessment of mortality sources of a selected marron population.
7. Piloting the identification of the impacts of major environmental variables affecting a selected marron population.

Final report

ISBN: 1 921258 94 2
Author: Martin de Graaf
Final Report • 2011-11-24 • 5.51 MB
2003-027-DLD.pdf

Summary

The distribution of marron in the southwest of Australia has seen many changes since European settlement. Reconstructions of their range from historical records suggested that marron inhabited the waters between the Harvey River and Denmark River. Due to translocation, their range has expanded as far north as the Hutt River and as far east as Esperance. Although at present marron still exist in all the original rivers within the southwest, their distribution within these rivers has contracted. Poor water quality, salinity, low rainfall and environmental degradation in the upper and lower reaches have restricted marron populations.

Historically, management decisions in the Recreational Marron Fishery have been based on fishery-dependent CPUE data collected using a logbook survey and phone survey. A critical assumption has been that the fisheries-dependent CPUE values were proportional to abundance. However, raw or nominal fisheries-dependent CPUE effort data are seldom proportional to abundance and relative abundances indices based on nominal and even standardised CPUE data are notoriously problematic and often provide little useful guidance for management. Although, the fishery-dependent programs provide high quality data on changes in the fishery, in isolation, these data provided limited information on the effects of fishing and the impact of fishery regulations on marron abundance. Standardising the fishery-dependent CPUE data for just one (introduction of snare-only areas during the 1990s) of the numerous management changes illustrated the significant bias in raw, nominal CPUE data. The use of biased fishery dependent data as measures for Recreational Marron Fishery productivity was probably one of the contributing factors limiting the success of developing predictive models using non-fishery variables (e.g. rainfall, river flow).

After a thorough review of (historical) sampling methods, a new fishery-independent annual research program using inexpensive box traps was implemented in 2006. Trapping allowed technical staff to sample several sites (2-4) simultaneously instead of just one site per night. More importantly, traps were set late afternoon and retrieved the following morning, removing the serious occupational health and safety issues associated with the historical late night (18:00- 1:00) sampling trips using drop nets and scoop nets. Furthermore, trapping removed the high level of subjectivity (e.g. operator skill level) associated with the traditional methods, especially scoop netting. Trap data appeared to be the most suitable as an index of relative abundance of marron. Interestingly, comparing trap catches with density data obtained through visual surveys using scuba revealed that at least over soft substrate in dams, trap catches can be used as both a measure of relative and absolute (#/m2) abundance.