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Government of Western Australia - Department of Fisheries
​Blue swimmer crab
(Portunus armatus)
Thursday 13 December 2018

Good recruitment of blue swimmers at Mandurah, but many crabs are too small to take

​Right now there are plenty of blue swimmer crabs in the Peel Harvey Estuary, but due to cooler temperatures experienced this year many of the new crabs are not yet at legal size.

Department of Primary Industries and Regional Development senior crab research scientist Danielle Johnston said a very cold winter and unseasonably cool spring had significantly impacted on the growth rate of new crabs in Mandurah.

“Winter temperatures were lower than the long term average and Spring was also unseasonably cool,” Dr Johnston said.

“Due to the shallow water depths, environmental changes, particularly temperature and rainfall, have a large influence on crab catch and catch rates in the Peel-Harvey fishery. 

“Undersize crabs are common in November and December, however, this year numbers are higher than the last few years and fishers need to avoid handling undersize crabs and return them to the water as soon as possible.”

The minimum size for blue swimmer crabs is 127millimetres and fishers are urged to use a crab gauge to measure their catch accurately. Crab gauges are available from tackle shops.

Supervising Fisheries and Marine Officer for Mandurah District, Jay Tonkin said fishers should never retain multiple crabs with the intention of measuring them later.

“This could damage the crabs and it is an offence if too many crabs are taken, or if any of the crabs are found to be undersize,” Mr Tonkin said.

“Fishers are encouraged not to scoop visibly undersized crabs then release them as this has the capacity to stress the juvenile crabs and potentially cause mortality.

“Taking or possessing undersized crabs can attract fines ranging from $200 to $1000 and, if prosecuted in Court, a penalty up to $5000 may be imposed, plus an additional mandatory penalty equal to $50 per crab, for each of the crabs that are subject to the offence.”

More information on rules, limits and gear is available in the department’s Crabbing for blue swimmer crabs in the west coast region, which is online at There are also a multi-lingual versions of the crabbing guide on the recreational fishing guides webpage

The current Mandurah crab fishing season ends on 31 August next year, and more legal size crabs will be available early next year when the new recruits have had time to moult and grow.
Anyone with information on illegal fishing activity should call FishWatch on 1800 815 507, so Fisheries officers can follow-up on anyone who doesn’t follow the rules.

Last modified: 23/12/2018 10:29 AM

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