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The environmental consequences associated with the biophysical and energetic inputs of fisheries are examined using six management scenarios. These scenarios represent different harvest targets, use of input controls and resource access commonly applied in fisheries management to meet different goals of sustainability (Table 3.1). Each scenario is represented by a rate of landings or

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catch per unit effort (CPUE) that is either targeted by management in the TSRL fishery (scenarios 1, 2 and 5), and/or is the observed result of management in a southern rock lobster fishery elsewhere adopting the relevant target or policy (scenarios 2,3, 4 and 6).

Scenario 1 reflects the situation in the TSRL fishery in 2010/2011 and therefore incorporates, among other input controls, a limit of 50 traps per vessel which was established prior to TAC management to control total effort. Although the TSRL fishery is quota managed, the emphasis in management up until 2011 had been on achieving higher catch rather than higher economic yield (Gardner 2012). As a result, the catch rate of 0.79 kg / trap lift in 2010/11 was interpreted as an observed catch rate under management targeting MSY. Scenario 1 serves in this analysis as the base case.

Scenario 2 retains the MSY harvest target but allows for the removal of the existing constraint on the number of traps allowed per vessel (Table 3.1). It was assumed the removal of the trap limit would lead to a doubling of traps per vessel, as occurred with vessels operating in the adjacent jurisdiction of Victoria, Australia, when this control was relaxed (Walker et al. 2012) (Table 3.1). In the Victorian fishery, the well capacity of vessels was not a constraint so it was assumed that changing the trap limit would not result in additional trips and fuel use. This assumption was also made on the basis that the fishery is managed with a TAC and thus catch rate (CPUE) would not be affected; that is, the same total number of trap sets would be required to take the same total catch but shared between fewer vessels. Increasing the number of trap sets per vessel has negligible impact on total fuel use per trip because travel between traps is typically around 100 m, which is small compared to travel between port and fishing grounds, often >200 km.

Scenario 3 represents a shift in the fishery to an MEY harvest target while retaining the existing trap limit per vessel. The catch rate value for this scenario was the observed catch rate in the nearby southern rock lobster fishery of CRA8 in New Zealand, which has pursued MEY management objectives since the late 1990s (Miller and Breen 2010). The result has been an increase in CPUE from less than the current Tasmanian rate to 3.8 kg / trap lift (NZRLIC 2011). This high catch rate appears biologically feasible in Tasmania given it is less than historic catch rates, which exceeded 4 kg / trap lift with less sophisticated equipment, in the 1950s (Hartmann et al. 2012). In scenario 4 the catch rate also reflects an MEY target in the fishery plus the trap limit is abolished.

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Table 3.1 Fisheries management scenarios examined using LCA for the Tasmanian southern rock lobster fishery. Each scenario represents a CPUE and goal related to different fishery or environment objectives

Fisheries management scenario Goal CPUE (kg/trap lift) Reference

MSY (baseline scenario) Maximise sustainable catch 0.79 Hartmann et al. (2012)

MSY & no trap limit Maximise sustainable catch and increase efficiency through removal of an input control

0.79 Hartmann et al. (2012)

MEY Maximise economic yield 3.8 NZRLIC (2011)

MEY & no trap limit Maximise economic yield & and increase efficiency through removal of input control

3.8 NZRLIC (2011)

MEY (interim target) Increase economic yield 1.4 Hartmann et al. (2012)

No-take area Conservation outcomes through area closure 0.59 Hobday et al. (2005)

Scenario 5 represents an interim harvest target (MEY interim). It is the target for 2020 adopted in the Tasmanian fishery in 2011 following a decision to target MEY as a management objective (Hartmann et al. 2012). It is intended to be a point along a pathway transitioning to higher catch rates closer to long-run MEY, as explored with scenario 3. The MEY interim scenario retains existing input controls in the fishery.

MPAs have been proposed for biodiversity conservation objectives in Tasmania (Marine and Marine Industries Council 2001) and their implementation in the state is therefore plausible. A final scenario, assuming reduced access of the fleet to fishing grounds due to the creation of a network of no-take areas, was based on the adjacent rock lobster fishery in Victoria. The Victorian fishery is the same biological stock as the Tasmanian fishery and therefore affected by the same broad scale trends in recruitment as Tasmania and South Australia on either side (Linnane et al. 2010). MPAs, covering 5.3% of coastal waters, were established in Victoria in 2002 without explicit fisheries objectives (Environment Conservation Council 2000). Prior to the implementation of these parks Hobday et al. (2005) predicted that in the absence of any accompanying reduction to the TAC, the loss of fishable area and biomass available to the industry as a result of the MPA, would reduce catch rates in the area open to fishing. No increase in fish abundance, biomass or egg production across the total of both fished and MPA areas was expected as a result of the MPAs, as it was assumed any increase in biomass inside the MPA would be offset by an equivalent reduction in biomass outside (Hilborn et al. 2006). In Victoria, exploitable biomass and catch rates fell, as anticipated, to a low of 0.59 kg / trap

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lift following MPA implementation, well below catch rates in South Australia and Tasmania (Hobday et al. 2005).

This experience is drawn on to illustrate the possible effect on CPUE in the TSRL fishery following reduction in resource access of a comparable magnitude, and assuming no other management change such as reduction in TAC or buy-out of commercial quota. In this scenario the management change is therefore restricted to the implementation of MPAs alone and the observed drop in catch rate that occurred in the adjacent Victorian fishery following introduction of MPAs is applied. However, it should be noted that MPAs are often implemented in association with other management changes and that outcomes are strongly influenced by these changes (Yamazaki et al. 2012).

Fuel use intensity (FUI), or litres of fuel required per kilogram of lobster caught, under each management scenario was calculated using the following formula:

FUIX = FUIMSY / (CPUEX / CPUEMSY)

Where FUIX and CPUEX are the fuel use intensity and CPUE for management scenario x, and FUIMSY

and CPUEMSY are the FUI and CPUE for the base case scenario (Table 3.1 and 3.3). Estimated CPUE

was also used to prorate the quantity of bait required per kilogram of lobster caught under each scenario.