Mills, D and Haddon, M and Gardner, C, Tasmanian Giant Crab Fishery 2004/05, Fishery Assessment Report, Tasmanian Aquaculture and Fisheries Institute, Hobart, Tasmania, 2006 (2006) [Government or Industry Research]
This report outlines giant crab fishery statistics for the 2004/2005 quota year and assesses performance against indictors defined in the Giant Crab Management Plan. This is the first assessment since the total allowable catch (TAC) was reduced from 103.5 tonnes to 62.1 tonnes for the 2004/2005 quota season. One of the assessable trigger points as defined in the Tasmanian Giant Crab Management Plan was breached in the 2004/2005 year. Total yearly catch was 49.3 tonnes, representing only 79% of the 62.1 tonne TAC, well down on the 90% trigger point. This low catch can be attributed to both a reduction in catch per unit effort (CPUE) when compared with the previous assessment period, plus reduced overall effort for the fishery. Effort in the 2004/2005 quota year was only marginally higher than the 2003/04 season, which was the lowest since the introduction of quota. Fishers have reported that this low effort was due to low beach prices making fishing un-economical. None of the trigger points relating to declines in CPUE were activated in the current assessment period. This compares favourably with the last assessment period where the trigger point relating to declines of greater than 20% over 2 years was activated in 3 of the 6 most active assessment areas. CPUE levels are now lower but stable. Bycatch of crabs retained by lobster fishers was not of concern for the giant crab fishery in the 2004/2005 season, with a reported catch of only 140 kg – well below the trigger point of five tonnes. The potential impact of trawlers remains a concern for operators in the crab fishery although limited information is available on removals and other mortality by trawling. Anecdotal reports from crab fishers indicate that trawling effort is much reduced from previous years. Trigger points relating to the size structure of the catch as landed at processors were not assessed, as processor splits are not available. Changes in catch size structure is now being obtained in greater resolution through on-board sampling by fishers with electronic loggers. This is the first giant crab assessment report to include stock assessment modelling, and employs a size-based model developed within a recently completed project funded by the Fisheries Research and Development Corporation (FRDC 2001/049). The model output suggests that without significant external impacts (e.g. an increase in trawl interactions) the current TAC of 62.1 t should lead to gradual stock rebuilding over the next 5 to 10 years. Conversely, under a TAC of 100 t, there is only a 50% chance of any stock rebuilding over the next 10 years. With a TAC of 100 t, there is also a 50% chance that the stock will decline over the next 10 years. Updates about ongoing and new research into crab habitat and trawl interactions, ghost fishing and reassessing the optimum size limits for the giant crab fishery are provided.