As mentioned above in B2 Background, one consequence of increasing concerns over ecosystem effects of fishing is that fisheries scientists, managers and fishermen are now being asked to consider not only the consequences of removing target species and non-target, by-catch species but also the ecological implications of disrupting habitats and the many species living in these systems. Unfortunately, much of the life on and in the seabed influenced by fishing gear like demersal trawls is unknown to the general public and, in Australia, much of it also remains unknown to science. While the species that comprise the biodiversity of these systems (sponges, ascidians, byrozoans, polychaetes, microscopic organisms, juveniles of commercially exploited species, etc.) have little charisma, public appeal or commercial priority, their role is a critical one because they underpin much of the local ecology. Add this to the fact that most of our commercial and recreational fisheries rely on the continued normal functioning of these ecosystems and it becomes obvious that the fishing industry itself should be (and in certain enlightened fisheries, are) concerned about these issues. That is, not only is it important for fishermen to understand these ecosystems in order to answer public outcries, it also makes good business sense for them to be actively involved in the maintenance of these systems upon which their fisheries depend.
Issues concerning biodiversity and ecosystem effects of fishing are key to most management plans for commercial fisheries in Australia where there are policies to manage in an ecologically sustainable manner. Ecological sustainability is not actually possible without sustaining the diversity of the system so the examination of processes sustaining biodiversity and the inclusion of such issues in management plans is a high priority for most fisheries agencies, including NSW Fisheries. The result from this is that ESD performance indicators are required in all management plans for NSW’s commercial fisheries - particularly the controversial estuarine prawn-trawl fishery.
Maintaining the ecological sustainability of estuaries is particularly important in a broader context because most of the species exploited in oceanic and estuarine waters rely on these estuaries for critical parts of their life cycle. For example, the very large Clarence River in NSW is known to be crucial for the juvenile stages of eastern king prawns and many species of fish that are exploited in oceanic waters. Protecting the ecology of such systems will obviously have major benefits for all fisheries based on such species - not just those exploited within the estuary.
The estuarine prawn-trawl fisheries of New South Wales also provide a unique opportunity to develop experimental designs and sampling protocols to address the issue of ecological impacts of trawling. These fisheries occur in shallow, calm water and, most importantly, already have various areas and times that are open and closed to trawling, providing excellent replicable treatments to incorporate in experimental comparisons. These factors combine to make these particular trawl fisheries ideal case-studies for studying impacts of trawling on ecosystems and to provide measurable indices of biodiversity that can be used as ESD performance indicators. The proposed research is particularly important in providing a model for how future studies (in more difficult habitats) may proceed.
As mentioned in B2 Background, developing solutions to problematic impacts of prawn trawling requires one to firstly identify and quantify the problem(s) and then assess the utility of various gear-based and closure-based management strategies designed to ameliorate these problem(s). This proposal seeks funds to begin this two-stage strategy in the Clarence River estuarine prawn trawl fishery by doing the first identification and quantification phase of the work.
