On the 14 December 2005 the Australian Government announced detailed proposals for the establishment of an extensive network of Marine Protected Areas (MPAs) in the South-east Region of Australia. The 14 candidate MPAs would cover more than 170,000 square kilometres of Commonwealth waters off Tasmania, Victoria, southern New South Wales and eastern South Australia.

Simultaneously, the Australian Government’s fisheries management reform, including substantial reductions in Total Allowable Catch (TAC) and the purchase of fishing licenses to remove effort from over fished fisheries, was extended to fishers – both Commonwealth and State licensed – who were affected by the creation of the MPA network. By running a single adjustment package it was reasoned that affected businesses need only go through one adjustment process (rather than two), and businesses in the South-east Region would not face a series of changes over several years.

The gross value of fisheries production from the South-east Region, at over $500 million per annum, represents an estimated 23% of the total gross value of Australian fisheries production. 

At the time of the announcement of the proposed MPA network, the boundaries of only two candidate MPAs within the 11 Broad Areas of Interest (BAOIs) had been discussed in any detail with the fishing industry. The Australian Government had brought forward the release of the proposed MPA network so that fishermen could make decisions about their future in the full knowledge of their operating environment – knowing the full extent of proposed exclusions from MPAs as well as knowing how their fisheries would be managed.

This report investigates the considerable impacts that these announcements pose for the fishing industry in the South-east Region and the considerable socio-economic implications for individual fishers who fish within the proposed areas, for entire fisheries, and on the overall supply of seafood to the Australian consumer.  On the understanding from the Commonwealth Department of Environment and Heritage
(DEH), that the proposed areas were negotiable, Industry and management agencies believed the most appropriate response was to characterise and validate the impacts and make a scientifically defensible case for alternatives such as boundary changes or alterations to the proposed MPA classifications.  These alternatives were designed to minimise the impacts on the fishing industry while at the same time not eroding the conservation values of the proposed MPA network in the region.

Exploitation rate is an important fishery assessment parameter linking catch to legal-sized biomass, the portion of the stock available for harvest.  Relative change in legal-sized biomass is a crucial performance indicator for the fishery as it measures the success of management outcomes.  Under the recently introduced Individual Transferable Quota Management System (ITQMS) in the Tasmanian rock lobster fishery, rebuilding of legal-sized biomass is a key management objective.  The assessment model that produces biomass estimates for this fishery is primarily dependent on commercial catch and effort data. 

The use of commercial catch and effort data for stock assessment relies on its de facto relationship with stock abundance.  However, the relationship between catch and effort data and abundance is not always constant or linear.  Improvements in fishing gear and technology can result in greater catch for a given amount of effort, unrelated to changes in the biomass.  Management changes and fishers’ behaviour can also affect the relationship between catch rates and biomass.  Under the new ITQMS introduced in 1998, catch is fixed and improved profits can be made by improving the return per unit of fish caught rather than by increasing the amount of catch through increased effort.  Thus fishing during periods when catch rates are low but price is high can change the catch effort relationship independent of biomass change.

Fishery independent surveys, using established sampling protocols and standardised fishing gear are a way in which catch rates can be standardised irrespective of gear efficiencies or fisher’s behaviour.  If these surveys can also produce accurate estimates of exploitation rate then accurate estimates of biomass can be achieved, provided the exploitation rate estimates are representative of the fishing grounds.  Fishery independent estimates of exploitation rate are thus a valuable way of validating model biomass estimates especially with the introduction of an ITQMS where the relationship between catch rates and legal-sized biomass was likely to change pre- and post-quota.

This project aimed to trial change-in-ratio (CIR) and index-removal (IR) techniques to obtain estimates of exploitation rate and biomass from broad scale regions in the fishery.

Keywords: southern rock lobster, change-in-ratio, index-removal, exploitation rates, tagging.