Domestic need

Within Australia, the regulatory frameworks for ecologically sustainable development (ESD) are at a critical point in their development. At the Commonwealth level, aquaculture will be directly affected by amendments to Schedule 4 of the Wildlife Protection (Regulation of Exports and Imports) Act 1982 (WPA); by the introduction of the Environment Protection and Biodiversity Conservation Act 1999 (EPBC); and in Queensland, by the introduction of the Great Barrier Reef Marine Park (Aquaculture) Regulations 1999. Environmental legislation regulating shrimp culture in Queensland is also currently under review.

The Standing Committee on Fisheries and Aquaculture (SCFA) has established a Working Group on ESD. The working group aims to develop ESD indicators for assessing fisheries and aquaculture in environmental, social and economic contexts. It is anticipated that the ESD assessment process developed through this work will form the basis for Environment Australia’s assessment of fisheries and aquaculture under WPA and EPBC. The first aquaculture case study was held on shrimp farming, 3-4 October 2000.

The Australian Prawn Farmers Association (APFA) convened a National Shrimp Farming Environmental Management Workshop 24-25 May 2000. One of the outcomes of the workshop was for Australian industry “…by 2010, to have technology and farming practices and strategies that achieve worlds best practice and nil tangible water quality impacts…APFA to establish a comprehensive strategy for ESD by fully supporting SCFA Case Study for developing ESD Indicators.”

Given these developments, the expert consultation is ideally placed to facilitate the development of appropriate ESD policy, legal frameworks and good management practices for shrimp culture in Australia. It is expected that the outcomes of the consultation will provide guidance and a common platform for the policy development currently being undertaken by SCFA, Environment Australia and the Australian Prawn Farmer’s Association. This will occur through the interaction of key Australian policy officers with international experts at the consultation, and through the guidelines arising from the workshop.

International need

In December 1997, FAO convened the Technical Consultation on Policies for Sustainable Shrimp Culture. This consultation brought together government delegates and observers from 12 countries of Asia and America accounting for about 90 % of the global production and major consuming countries.

The Consultation noted that the achievement of sustainable shrimp culture is dependent on effective government policy and regulatory actions, as well as the co-operation of industry in utilising sound technology in its planning, development and operations. In this regard, the Consultation recommended that: FAO convene expert meetings to elaborate best practices for shrimp culture and the legal and other regulatory instruments for coastal aquaculture.

Four of the eight fishing industry sectors have identified pollution as one of the priorities for improvement. Although the pollution types and sources were not further defined, the impacts from persistent organic pollutants are becoming more common worldwide. Toxic effects arising from exposure to chemical pollutants are frequently reported. In addition, contamination by these chemicals can lead to discrimination and/or rejection of the product in the marketplace. The need is for a properly funded study that examines the quality of inshore seawater in a defined area and from which links can be established between cause and effect. For the reasons set out below, the study proposed is seen as Stage 1 of a multi-stage process which will enable the Fishing Industry to understand where it stands currently as far as water pollution by organic chemicals is concerned and the impacts these chemicals might have on specific ecosystem components.

The focus of stage 2 would be to examine the impact of bio-available inorganic chemicals and, separately, increased levels of nutrients on specified key ecosystem components. A subsequent stage could examine the impact of identified industrial chemicals on appropriate indicator species. The aim must be to appreciate the sensitivity of (South) Australian marine ecosystems to pollution from a variety of sources and the impact on market share.

Stage 1.
There is increasing evidence from other States in Australia, and worldwide, that persistent herbicides arising from terrestrial activities are impacting on the growth and productivity of inshore seagrass beds. The toxicity of agricultural chemicals, principally insecticides, has been demonstrated on fish species that are indigenous to the Northern Hemisphere but no study has looked at the toxicity of persistent agricultural chemicals to species found in Australia. And, more importantly, the toxicity of widely used persistent agricultural chemicals to species of commercial importance in South Australia has not been studied.

Recruitment of juveniles from the inshore nursery areas where persistent agricultural chemicals are most likely to be found could be significantly compromised. Modern pesticides, intended for terrestrial use, are toxic at extremely low concentrations.

The levels of persistent herbicides found in marine environments elsewhere in the world are significant, and similar levels would be expected to occur in Australian inshore waters given the extensive use of herbicides in Australian agriculture. The toxicity of persistent herbicides to inter-tidal seagrass species has not been studied in Australia.

A study linking the concentration of a key persistent organic insecticide in the soil, its concentration in the adjacent marine environment and its toxicity to a key marine indicator species such as the prawn, represents a good model for the study of the impact of a non-point source pollutant over a relatively small area.

The contribution by wind-blown topsoil from adjacent farm areas, which can act as a carrier of considerable quantities of adsorbed persistent organic pesticides has not been examined in South Australia. The role of dust-storm events in the transport of toxic chemicals elsewhere in the world is recognised. The concentration in seawater of persistent organic pollutants such as insecticides has not been determined on a seasonal basis.
Dose-response data for a major persistent insecticide and a key indicator marine species such as prawns, combined with knowledge of the concentration of the pesticide in seawater, will provide a scientific basis for proposing modification of land management practices.

The demonstration of significant levels of persistent pesticides in fine farm topsoil and identification of those pesticides in seawater, combined with demonstrated toxicity effects on a key marine species of commercial significance, would provide further support for proposing changes in land-care strategies designed to mitigate these inputs.

An examination of which fisheries species are sustained by seagrass plant production has been highlighted as a major research priority in the recent reviews of fisheries habitat research gaps by Cappo et al. (1997) and Butler & Jernakoff (draft report to FRDC). The recommended method in Butler & Jernakoff for tracing seagrass production to fisheries species is stable isotope analysis. Coastal and fisheries managers currently consider seagrass to be valuable, nevertheless there are many seagrass meadows under threat and still being lost. An argument can be developed, supported by current scientific evidence, that many important fisheries species are not reliant on seagrass and that their numbers actually increase upon the decline of seagrass. Estuarine and offshore fisheries species that do not appear to be dependent on seagrass might actually be so, but indirectly; they may be deriving their food from animals in a trophic web that is sustained by energy (carbon) and nutrients (e.g. nitrogen) transported from seagrass meadows. Another estuarine habitat, mangrove forest, has previously been touted as generating plant production that drives food webs elsewhere in estuaries and offshore. Recent evidence from Australia and Asia suggests this is not so; mangroves seem to sustain only species living in mangrove areas. The question whether seagrass production is the major source of primary production sustaining fisheries production needs answering. The best method for tracing where fisheries species gain their nutrition is stable isotope analysis.

The proposed research will be done in Moreton Bay and Hervey Bay. These bays are of extraordinary importance to Queensland fisheries, with Moreton Bay alone comprising up to 30% of the total Queensland catch of inshore recreational and commercial species (Tibbetts & Connolly 1998). There are also important fisheries in deeper waters adjacent to these bays. Both bays have extensive areas of seagrass, but also mangroves, saltmarsh and occasional reefs offshore. They are also suffering ongoing seagrass loss.

Fishery Management Plans are currently being developed for all major fisheries in Queensland. In the next few years, these plans will become the legal framework within which management practices are applied. Limit and target reference points have been developed and put forward as key assessment and management tools in all of these plans. Methods used to estimate the reference points have generally been ad hoc and based on un-standardised catch and effort data.

Clearly, there is a strong need to test these reference points.

In the Queensland Trawl Fishery Management Plan (east coast - Moreton Bay) 1998-2005, the limit reference points are based on a comparison of the average logbook catch-per-unit-effort from 1988-96 with the relevent year's catch-per-unit-effort. At present, this comparison of CPUEs takes no account of changes in effective effort.

However, effective fishing effort continually increases, even though the number of licence holders or total number of days fished each year may remain constant. This continual “effort creep” is characteristic of trawl fleets and is due to fishers adopting technological improvements in fishing practices, such as GPS and plotters. A recent study of the northern prawn fishery indicates that when GPS and plotters are used concurrently, relative fishing power increases by 7% over boats without such equipment (Robins et. al. in press).

We propose to standardise the effort of the trawl fleet, which is capital intensive and would therefore be most affected by technology advances. Two major trawl fleets operate within the Queensland region, the Torres Strait trawl and the Queensland East Coast trawl licensed fleet. In terms of value, the most important species captured by these vessels are tiger prawns, eastern king prawns and saucer scallops. AFMA and the Torres Strait Scientific Advisory Committee see a priority need that catch rate analysis of the Torres Strait tiger prawn fishery be undertaken. The prawn Working Group for Torres Strait has discussed this issue of possible changes in effective effort and the managers are of the opinion that this issue needs to be investigated. The small size of the fleet will simplify analysis compared to analysing the full Queensland tiger prawn fishery.

In summary, therefore, effective reference points must be clearly defined and relate to a management system that uses a catch-per-unit effort series adjusted for changes in fishing power.

Coastal areas of Australia, especially those close to urban areas, are under increasing pressure from industrial and tourism developments, and the associated infrastructure to support them. These shallow-water coastal and estuarine areas will also continue to be the focus of attention by the recreational and commercial fishing sectors. An understanding of the impacts of damage to key intertidal habitats will allow managers to minimise the adverse impacts and developmental degradation on Australia's fisheries resources.

There is currently no detailed information available on the specific effects of loss or damage to intertidal estuarine habitats on the animal assemblages that utilise these habitats, despite the recognised importance of the habitats and the benthic invertebrates to fisheries resources. Studies which have examined the effects of damage to subtidal habitats have shown important links to fisheries utilising these habitats (e.g. Sainsbury et al., 1993). Similar studies should be a priority for critical intertidal estuarine habitats. Although this project focuses on damage to intertidal habitats caused by bait-harvesting, the results of this work will be applicable to other sources of damage to these habitats, providing an important database establishing causal relationships between effects on the physical structure of the habitat and impacts on the associated animals.