Reefs represent important habitats for commercially and recreationally exploited species under Tasmanian jurisdiction. In Tasmania, shallow reefs (25 m) are significant to commercial and recreational fisheries for scalefish and invertebrates. These include live-fish fisheries for banded morwong (gillnet) and wrasse (trap and line), as well as recreational and commercial gillnet fisheries for species such as bastard trumpeter, striped trumpeter and blue warehou. Other species including jackass morwong, various leatherjackets and boarfish, are also relatively commonly caught on shallow inshore reefs. Most of these species also occur at greater depths but as only striped trumpeter are subjected to a targeted (line) deepwater fishery; deep reefs are therefore assumed to be important refuges from fishing pressure. While recent research has improved our understanding of the population biology of some of these species, management of these fisheries is primarily based on characteristics observed from shallow reefs. The lack of quantitative information on the significance of deep reef habitats as refuges and/or their role in population structuring limits our ability to undertake informed risk assessments of the impacts of current fishing practices and evaluate alternative management options.

While the structure, composition and functioning of shallow-reefs (10m) and their associated fish communities has been studied extensively, the ecological importance of deeper reef ecosystems has not been investigated apart from recent baseline studies of offshore Commonwealth MPAs. Linkages and associations between fish communities in shallow and deeper reef areas remain a distinct knowledge gap.

The need for this project was identified by fishery managers and industry and addresses high priority strategic research areas identified by both state and national fisheries organisations. It is research that targets a high priority need across Australian fisheries: understanding the effects of fishing activities on fish and their ecosystems. The need for research is compounded in shelf-break habitats due to: (a) scarcity of basic information about shelf break habitats, (b) slow growth of many species in this region implying less resilience to impacts, (c) interaction effects between different sectors that may compound impacts.

The research need on addressing interaction between different sectors will be specifically addressed here in relation to the interaction between trawl and crab trapping sectors. This interaction between different fishing sectors is not unusual and is likely to be repeated in the future – work conducted here will assist in providing a template for resolution.

Understanding shelf-break habitat for sustainable management of fisheries with spatial overlap was identified as the number 1 research priority for Tasmanian crustacean research by both DPIWE and representatives of the Tasmanian crustacean fishing industry at the Tasmanian Crustacean Research Advisory Group.

The project focus is also consistent with strategies developed by the Commonwealth agencies involved in management of industries based around the shelf-break: the Commonwealth Government and the Department of Agriculture, Fisheries and Forestry Australia (AFFA). It is targeted to the FRDC program of Natural Resource Sustainability through the strategies of “Interactions between fish and their ecosystems” and “Effects of fishing activities on fish and their ecosystems”.

Current age determination methods, even when aided by image analysis software still depend on interpretation by an experienced "reader". The process of ageing is also laborious, time consuming and hence, relatively expensive. For production ageing, where there is an ongoing requirement for age estimates, there is a problem of consistency of interpretation. At present, when readers change, there is a substantial training and verification period needed to ensure that the new reader is interpreting otolith structure in a consistent and correct manner. Automatic ageing would have the primary advantage of being a far more objective method than is possible with even the best training, reducing discrepancies both between readers and organisations. This factor will increase the precision of estimates and therefore provide greater confidence for the stock assessment process. Benefits associated with the development of this technique also include the reduced sample processing time which would increase the number of samples able to be processed and hence, reduce the cost.

The pilot project which has been completed has demonstrated the potential for artificial neural networks to objectively and consistently classify samples of some species. With refinements of the system, it should be applicable to any species for which production ageing is required.