Biology, fishery assessment and management of shared snapper fisheries in northern Australia and eastern Indonesia

• Department of Primary Industries and Energy, Australia
• Centre for Agro-Socio Economic Research and Development, Indonesia
• Research Institute for Marine Fisheries, Indonesia
• Central Research Institute for Fisheries, Indonesia
• Directorate General of Fisheries, Indonesia
• Department of Primary Industry and Fisheries, Northern Territory, Australia

Red and goldband snapper stocks are harvested in both Australian and Indonesian waters, employing a variety of methods including trawl, drop-line and bottom longline. Little has been known of the stock structure, distribution and movement of these shared fish stocks. Furthermore, data on the population biology and on commercial catches were inadequate. These data are crucial for stock assessment and management of stocks.

In planning the ACIAR project it was recognised that those fishing Australian waters targeted both red and goldband snapper, while the latter is sought after by the Indonesian fishery but any other miscellaneous species were also landed. It was initially assumed that in Indonesian waters the artisanal fishery was likely to be taking a significant portion of the red and goldband catch, although there was a large fleet of foreign vessels in Indonesian waters. This assumption was tested in the course of the project.

The project aimed to provide advice on stock structure and biology relevant to the management of red and goldband snapper species in northern Australia and eastern Indonesia, and also to describe the social and financial structures that might be affected by future management strategies for the fisheries; further, to assess the state of the snapper fisheries and explore the types of complementary management strategies suitable to ensure their long-term sustainability.

The project was divided into three main strands. The first was the biological research, where scientists investigated the population genetics of both snappers by establishing frequencies of certain genes at known locations on the chromosomes. They also described the reproductive biology by examining sample animals caught at various sites around Indonesia and Australia and-for red snappers only-they tracked movements and located nursery habitats.

The second part of the project concerned socioeconomic research. Here the team described the structure and organisation of the snapper fishery and postharvest chain in Indonesia, in order to assess the potential constraints on negotiating and implementing management options. The team assessed the importance of snapper fisheries for industrial and artisanal fishers, and undertook a survey of relevant regulatory agencies and the role of state development plans and policies.

The final part of the work determined the sustainability of current catches and provided the technical input for assessing the effects of different management strategies on the stocks. From the information obtained the researchers developed a framework for complementary conservation, management and use of the shared stocks.

The project achievements have already made a significant contribution to the future management of the shared fish stocks of Australia and Indonesia. Employing a range of analytical methods the scientists demonstrated that, while separate stocks of red and gold snapper exist and are fished in Indonesian waters, in the shared fishery red and goldband snappers are fished jointly. They gathered a wealth of information about the spawning, growth rates and age composition of different populations. A significant finding was that red snapper aged 5-6 years collected from Indonesian waters were on average larger than fish of the same age collected from Australian waters.

The scientists determined through yield- and egg-per-recruit analyses that the fishnet fishery placed the future sustainability of the snapper fishery at considerable risk, largely because it caught too many small fish. They also found that the type of fishing gear used by the Australian fishery tended to catch greater quantities of smaller fish, and recommended investigation of traps to determine their effect on catches. The scientists' use of a biomass dynamics model produced further evidence that the current levels of catch of red snapper would be unsustainable in the longer term.

At the start of the project the scientists found that the data collection system in use by Indonesia was not producing reliable estimates of catches of the three snapper species. An improved system of data collection enabled the discovery that the small-scale artisanal Indonesian fishery for snapper took a relatively small annual catch compared with those taken by the bottom longline and fish net boats.

Researchers found that in Indonesian waters the licensing system was inadequate for vessels greater than 30 tonnes. In fact Indonesia derived very little economic benefit from catches taken by the net fishery and was providing a fuel subsidy to the fish net boats from Thailand. Now changes introduced in the course of the project have led to a much improved licensing system.

The involvement of policy/decision makers and fishery managers within the project gave them an awareness of the science, and in return they provided advice on the impact and suitability of alternative strategies for future management of the fishery.

The project's success has been the catalyst for further collaborative research projects, on tuna and on sharks and rays.