The need for strategic R&D in the mapping of coastal seabed habitats supporting fisheries and linking fisheries assessments with such mapping has been identified through several Commonwealth (FRDC - 95/055, 98/223 94/040 and 94/037) and in the Tasmanian Marine Environment Strategic Research Plan (1999-2004.

These needs are reflected in this proposal that aims to provide spatial information on abalone habitats in several key fishing blocks relevant to both site specific fishery independent abundance surveys and stock assessments at the block scale.

The need for fishery independent abundance surveys and assessment of physical and species interactions for abalone in Tasmania are high priority issues in the Tasmanian Abalone Strategic Research Plan and a review of abalone research needs (FRDC project 98/170). This is reflected in the current abalone FRDC project (2001/074) and ongoing abalone abundance surveys. The project proposed here will significantly contribute to this research by providing fine-scale maps of the biological and physical structure of abalone habitats which will help to optimise abalone abundance and population studies by having better criteria on which to select survey sites. It will also further improve abalone assessments by providing estimates of reef habitat for several key blocks and assisting in the correlation of environmental and habitat variables on catch rates and population parameters. In particular, there is a need to examine the structure of reef habitats in north-east Tasmania where many areas have become ‘unproductive’ for abalone in recent years and there are considerable urchin barrens present, the of which is required through detailed mapping.

In addition, further R&D is needed in the area of cost-effective acoustic and video assessment techniques. This project aims to advance this R&D and continue the transfer of technology to other agencies that TAFI has been progressing. The increase in coastal mapping in Australia also requires a framework and consistency for classifying habitats at a range of hierarchical scales. This is being progressed in the FRDC project 2002/097 ‘Development of national habitat classification framework’, which will require a significant input from mapping projects such as proposed here for the classification scheme to be comprehensive and representative.

There is a common need in the assessment of all fisheries to obtain precise estimates of exploitation rates and/or biomass. In the Tasmanian rock lobster fishery, biomass is a key performance indicator and change in biomass is the primary driver for recommendations of future Total Allowable Commercial Catch (TACC) allocations by the Fisheries Advisory Committee. In recognition of this need, both the Tasmanian
Government (1992-1997) and FRDC (1997-2001) have funded projects to investigate methods to estimate biomass independent of the fishery.

Fishery independent estimates are essential because estimates derived from fisher’s catch and effort are often biased as exemplified by the change in the link between catch rate and abundance following the introduction of the ITQ management system in Tasmania (FRDC 1999/140). Although initially promising, exploitation rate and biomass estimates based on changes in the population during the fishing season proved unreliable (FRDC 1997/101). Both the Industry and Managers have identified the need to explore new methods to obtain precise estimates of these important performance indicators.

Multi-year tagging models have been identified as a promising way of estimating these parameters because they address the failings (variable catchability and recruitment) in the population derived estimators. Initial trials in northwestern Tasmania proved very successful and support the potential of this approach. However, tag returns from fishers are unpredictable and there is an immediate need to
determine ways of improving tag reporting rate to optimise the output of tag based models. Furthermore, the models applied to northwestern Tasmania relied on a minimum of two tagging events occurring each fishing season. As each tagging event occurred during a different period of the moult cycle, there is a need to validate the tag retention and tag induced mortality rates associated with these different tagging times. Other factors relating to size, sex, damage and their interactions with different tagging times also need further investigation. A careful evaluation of other means of improving the precision of estimates from tagging models is seen as necessary, prior to the implementation of a large scale tagging program.

Validating the assumptions associated with the use of tagging models, demonstrating ways to test for these assumptions and the precision of fishery assessment outputs is needed prior to recommending these models for use in other fisheries.

If the long-spined sea urchin behaves in Tasmania as in NSW, then large tracts of reef habitat will be destroyed and concomitant reductions in abalone and rock lobster fisheries are likely. Given fixed quotas, this will have the effect of increasing effort in productive habitat that has not been affected by urchins. It is imperative to assess whether the urchin is likely to behave in Tasmania as in NSW, and therefore whether it poses a significant threat to reef-based industries in Tasmania.

The pilot project proposed here will provide this initial assessment in establishing baseline information on the distribution of C. rodergsii 'barrens' (i.e. the current extent of the problem) and the urchin itself (i.e. the potential extent of the problem) on the east coast, and will determine whether abalone and rock lobster populations are reduced on relatively recent barrens.

If the threat posed by the urchin is significant, then it will be important to address possible responses to the problem while the extent of barrens may still be relatively circumscribed. The baseline data obtained in this project will also assist in assessing whether development of an urchin industry might be a suitable response to manage the problem.

The work outlined here is a necessary first step prior to a more expansive research program to identify (1) mechanisms triggering destruction of algal habitat, (2) the importance of interactions between the urchins and rock lobsters, abalone and algae in underpinning macro-dynamics of rocky reef systems and the population dynamics of commercial species, and (3) management responses to mitigate the impact of the urchin.

Abalone stocks are vulnerable to localized depletion, followed by fishery collapse. In Australia, assessments of abalone fisheries have been written in all abalone-producing states. However, except in NSW (Worthington, 1998), the basis for those stock assessments is generally an anecdotal interpretation of un-standardized commercial catch-effort data and, sometimes, information on the size-composition of the catch. This information is often combined, in an informal way, with research data to give an impression of the status of the stocks. Performance indicators used do not tend to be biologically based. Most importantly, the sustainability of current catch levels is not known with any confidence. Meeting the guidelines from Environment Australia with regard to sustainability of fisheries will require a more formal assessment for such an important fishery.

The development of FRDC project 1999/116, to develop a National Abalone Model, is an attempt to answer the obvious need for a valid model. Currently, New South Wales is the only state where a stock assessment model is being used as the basis for fishery management decisions in an abalone fishery. In Tasmania, The inputs currently available to the model being developed include fishery-dependent catch-effort data, fishery-dependent length-frequency data, research length-frequency data, and estimates of biological parameters. The crucial data, missing from the inputs to the model, is a fishery-independent index of relative abundance. The survey techniques used in NSW and in Victoria have been found incapable of producing estimates with sufficient
precision under Tasmanian conditions. There is thus a need to develop an optimum combination of fishery independent indices of abundance that will have application in the full range of Tasmanian abalone habitats. In addition, Tasmania's raw catch-effort data must be standardized prior to its use in a formal assessment model because of the high variability in catch rates between divers, areas, season, and other factors.

Specifically this project will:
(1) better determine the relationship between catch-rate and abundance. This is needed for realistic standardisation of catch and effort statistics;
(2) improve our understanding of the differences between commercial size-composition data and the actual size composition of the legal size abalone left after fishing (selectivity v availability). Such data are a key ingredient of stock assessment models;
(3) assess the accuracy of diver logbook data. This will help ensure that the data requested via industry logbooks focuses on the most appropriate questions and will assist with appropriate standardisation.

The information gained will underpin the development of credible, realistic fisheries models for abalone, which will consequently improve the confidence with which abalone fisheries are managed. Increased confidence in fisheries management decisions will have measurable economic benefits.