Fisheries Research Report [Western Australia] No. 217, 2012 133
Indicator Value Management Response Greater than 75 per cent
probability that it is still greater than the threshold value in five years.
No management action is required.
Less than 75 per cent probability that it is still greater than the threshold value in five years.
Initiate a review process that will generate recommendations regarding the most effective forms of management response, to be completed within three months.
Implement management measures to ensure the egg production indicator values in the fifth year are greater than the threshold value, with a 75 per cent probability.
In general any stock rebuilding strategy should include the following (adapted from Department of Agriculture, Fisheries and Forestry 2007 p44):
clear specifications of objectives, including targets and time frames;
performance criteria to evaluate the effectiveness of the strategy against its objectives;
actions required to achieve the objectives of the strategy;
key threats to recovery of the stock or to the economic performance of the fishery and strategies to counter them;
the estimated duration and cost of the strategy / process, including apportionment of cost across government and other stakeholders;
parties affected by the implementation of the strategy; and
any significant related environmental impacts (positive or negative) arising from the implementation of the strategy.
early larval life. These low levels are yet to be explained. Further research is underway to examine the potential causes (Section 7.1).
The most recent completed settlement season (2010/11) has seen a marked improvement in the levels of settlement at most sites throughout the fishery, with settlement levels fitting with the historical relationship with water temperature. These levels are still below the long-term average since water temperatures in February/April 2010 were cooler than average and very few storm fronts crossed the West Australian coast during late winter/spring of 2010.
Water temperatures for February 2011 are well above average as a result of a strong Leeuwin Current associated with the La Nina conditions. The effect of these warmer conditions have historically been associated with improved settlement in the following year (2011/12) which will be monitored later, starting in about August 2011.
Recent Management Changes
The fishery has changed management systems from an input to a catch-limit controlled fishery, with a nominal Total Allowable Commercial Catch (TACC) of (5500 t) being imposed for the 2010/11 fishing season. Each fishing unit has been allocated a zone-specific portion of this TACC and input controls (e.g. pot usage and temporal closures) have remained.
Proactive management measures were introduced in 2008/09 and 2009/10 as a result of the low puerulus settlement, resulting in nominal fishing effort reductions of 44 and 72% to ensure a carryover of legal size from these reasonable catch years into the predicted low catch years to assist maintain the breeding stock above threshold levels over the coming five year period. This resulted in catches of 7600 and 5900 t in 2008/09 and 2009/10, respectively, compared to the catch predictions based on historic (2007/08) levels of fishing of 9200 and 8700 t, respectively.
These large reductions in catch (up to 4400 t) resulted in significant increases in residual biomass over the last two seasons which have flowed into the available stock for the coming predicted low recruitment years commencing in 2010/11.
Breeding Stock and Harvest rate by zone Zone A
• The model-derived harvest rate estimate has declined markedly in recent years due to management changes since 2008/09. It is predicted to remain relatively steady over the next five fishing seasons under current levels of catch (Section 5.5).
• The 2010 IBSS survey in this zone was compromised due to a GPS plotter malfunction.
Attempts will be made using the 2011 survey to develop a scaling factor to adjust the 2010 catches relative to those that would have been expected if the pots had been set correctly. The previous survey indicated a high level of egg production.
• The model-derived egg production index is currently well above its historical minima. The model predicts this index will remain well above its threshold reference point with 75%
certainty over the following five fishing seasons under current levels of catch (Section 5.5).
Egg production in Zone A (Abrolhos Islands) is above threshold and limit reference points
Fisheries Research Report [Western Australia] No. 217, 2012 135 Zone B
• The model-derived harvest rate estimate has declined markedly in recent years due to management changes. It is predicted to remain relatively steady over the next five fishing seasons under current levels of fishing effort (Section 5.5).
• The fishery-independent BSI for 2010 was amongst the highest on record (Section 4.3), and increased from the previous season’s measure. The high 2010-point is not considered the result of extremely favourable environmental conditions during the survey.
• The model-derived egg production index is currently well above its historical minima. The model predicts this index will remain above its threshold reference point with 75% certainty and its limit reference point over the following five fishing seasons under current levels of catch (Section 5.5).
Egg production in Zone B (Northern Coastal) is currently above threshold and limit reference points and is predicted to remain relatively steady with > 75% certainty over the following five seasons under current levels of catch. Harvest rates have decreased in recent seasons and will continue to remain low over coming years under current management arrangements.
Zone C
• The model-derived harvest rate estimate has declined markedly in recent years due to management changes. It is predicted to remain relatively steady over the next five fishing seasons under current levels of fishing effort (Section 5.5).
• The fishery-independent BSI for 2010 was the highest on record (Section 4.3), being well up from the previous (2008 and 2009) year’s estimates. Unlike the 2008 estimate however, the 2010-point is not considered the result of extremely favourable environmental conditions during the survey.
• The model-derived egg production index is currently well above its historical minima. The model predicts this index will remain well above its threshold reference point with 75%
certainty and its limit reference point over the following five fishing seasons under current levels of fishing effort (Section 5.5).
Egg production in Zone C (Southern Coastal) is currently above threshold and limit reference points. This index is predicted with > 75 % certainty to remain relatively high over the subsequent five fishing seasons under current management. Harvest rates have decreased in recent seasons and will continue to remain low over coming years under current management.