Southern Rock Lobster
2020/21 Stock Status Summary
Tasmanian Rock Lobster Fishery
Percentage of egg production relative to unfished level (limit reference point)
Percentage of biomass relative to unfished level (limit and target reference points).
The Tasmanian Southern Rock Lobster fishery has a long history of exploitation. Low stock levels saw the introduction of increasing management controls including size limits, pot limits, vessel limits. Depletion to a very low level in the 1990s resulted in the introduction of a total allowable catch limit (TAC). The commercial component of the TAC is traded through an Individual Transferable Quota (ITQ) system. Recreational catch is controlled through input controls and the statewide recreational component of the TAC is rarely reached.
Following the introduction of the ITQ system the stock rebuilt consistently to the mid 2000s at which point a reduction in recruitment saw a rapid recline to record low levels. To address this the TAC was reduced by approximately one third and the stock has since recovered to it’s current level which is at or near to a thirty year high. Egg production is at 37.7% of the unfished level which is well above the 30% limit reference point. Due to connectivity with the broader stock the level of egg production across the stock’s entirety needs to be considered, this is lower but remains above 20% of the unfished level which is the reference point set in the Status of Australian Fish Stocks Reports (https://fish.gov.au/report/294-Southern-Rock-Lobster-2020).
Statewide biomass is above the 20% limit reference point and CPUE (an indicator of biomass) is at a thirty year high. However, the stock is recovering from a highly depleted state. A rebuilding target of 25% of biomass by 2026 has been established and is considered an interim rebuilding target with a higher subsequent target level of biomass remaining to be determined.
On the basis of the above evidence the current stock status with particular emphasis on the Tasmanian component of the stock is unlikely to be depleted and recruitment is unlikely to be impaired.
The TAC is set on an annual basis at a level that ensures that egg production remains above the 30% statewide limit reference point and to ensure that the fishery remains on track to reach the interim rebuilding target. This is evaluated through an integrated stock assessment model that combines all sources of information available to produce the best assessment of the current stock state and the predicted response to future management decisions. A key component of this is consideration of the robustness of the management approach to different future recruitment scenarios (a sensitivity analysis).
The management measures discussed ensure that the exploitation rate is maintained at a level that will allow ongoing stock rebuilding, as such the fishing mortality is unlikely to cause the stock to become recruitment impaired now and into the future.
There is a high confidence that the stock is well above a depleted level where recruitment is impaired and current management arrangements will ensure that the stock is able to continue to recover. Consequently the Tasmanian Southern Rock Lobster stock is classified as Sustainable.
In addition to meeting statewide target and limit reference points the status of the stock around Tasmania is considered annually. Management aims to provide good abundance around the state for commercial and recreational fishers in each area and healthy biomass for ecosystem function and non-extractive users throughout Tasmania.
Improvement in CPUE over the last few years has been distributed across all stock assessment areas. Areas in the East Coast Stock Rebuilding Zone (SRZ) initially showed limited CPUE increase despite dramatic catch reductions. Then after a period of rapid CPUE increase, CPUE fell again in 2019/20 and 2020/21. Consequently area 2 and 3 remain well below the area specific interim rebuild target of 20% virgin biomass stock and a further catch reduction is required to keep Area 2 on track for meeting this target by 2023. To achieve this the total catch in areas 1, 2 and 3 (combined over both sectors) would need to be substantially reduced. There are a number of factors contributing to this including recreational over-catch. However, the primary factors are a record low abundance of undersize lobsters coupled with the limited time remaining before the 2023 target year. It should be noted that the target is still expected to be achieved (i.e. rebuilding is expected to continue), but 2-4 years behind schedule.
Due to the long pelagic larval period (up to two years), egg production in different areas of the fishery is not closely linked to future recruitment in that region. Recruitment is affected by patterns in larval dispersal and it’s known that the most important regions for larval sources tend to vary from year to year. The appropriate management response to this is to ensure that healthy egg production of at least 20% of the unfished level is maintained in all areas. Area 5 is the only area falling below this level, a regional size limit was put in place to address this in late 2019 which is expected to ensure a steady rebuild to over 20% by 2026.
Stock Assessment Draft Summary Reports
Below are links to the stock assessment draft summary reports that are produced each year to communicate initial stock assessment findings.