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Government of Western Australia - Department of Fisheries

Blue swimmer crab management

​The blue swimmer crab fishery incorporates commercial and recreational sectors. We manage both together to ensure sustainable fisheries.

WA’s annual blue swimmer crab commercial catch usually exceeds 1,000 tonnes. Hundreds of tonnes are also caught by recreational fishers.

We manage fishing through measures including commercial licences and area and seasonal crabbing closures. A minimum legal size limit ensures crabs can spawn at least once before they may be taken.

Concern about low stocks led to a complete closure of Cockburn Sound in 2006 and a seasonal closure of the Peel-Harvey Estuary in 2007. Improvement in the stocks resulted in a partial (seasonal) re-opening to crabbing in Cockburn Sound in 2009.

Continuing improvement led to a further easing of restrictions in Cockburn Sound in 2011/12, including extensions of open seasons for commercial and recreational crab fishing.

In Shark Bay, a ‘marine heatwave’ in the summer of 2010/11 appears to have led to a reduction in crab stocks. Fewer young crabs survived to enter the adult stocks after ocean surface temperatures reached 4-5º C above average.

To help stocks rebuild, we negotiated a voluntary ‘no take’ of crabs with commercial fishers from late April 2012.

Research survey results will be used to reassess the situation and we are drawing up performance measures to determine when stocks can support commercial fishing again.

Management action, including catch and/or ‘effort’ (amount of fishing) targets, will be considered when fishing resumes. Recreational fishing hasn’t been restricted due to its relatively low impact on stocks.

Monitoring, assessment and research

To protect stocks into the future, we monitor the status of blue swimmer crab populations and fishing levels.

 Blue swimmer status 2011 - major WA crab fisheries

​Location Status of crab stocks​ Amount of fishing​
​Cockburn sound Adequate ​ Acceptable ​
​Peel-Harvey Estuary Adequate ​ Acceptable ​
​Shark Bay Under review ​ Under review

We use various methods to monitor crab stocks including trapping and trawling surveys which provide information about the abundance, size and reproductive condition of the animals in each population. 

Another method is collecting data about effort and catch rates on board commercial vessels. Research staff measure the retained and non-retained catch. We also make estimates of recreational catch and effort from fishing surveys.

By analysing catches, and comparing this information with knowledge about the crabs’ biology and the size and gender structure of the population being fished, researchers are able to draw conclusions about the stock's status.

Research is continuing into the relationship between different blue swimmer crab populations. This requires an understanding of growth and movement patterns, and the impact of human activities and environmental factors on breeding and growth.

In 2011, in Shark Bay, an external scientific review of blue swimmer crab research data highlighted stock trends and gaps in knowledge. An accurate assessment of sustainable catch levels could not be made due to insufficient scientific data. As a result, management options for commercial fishing are being considered until a more thorough stock assessment can be done.

A fishery-independent research project funded by the Fisheries Research Development Corporation to assess the stock status of crabs in Shark Bay began in 2012 and will run for three years.

Last modified: 30/01/2015 4:32 PM

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