CRAB fishing is now prohibited in the Peel-Harvey Estuary until November 1, with a set of new warning signs erected on Monday.
The signs advise against crab fishing during the annual closure period, which runs from September 1 to October 31.
The annual closure ensures juvenile crabs can grow to reach an appropriate size for legal fishing.
The signs come after a recent Department of Fisheries report found an upward trend in crab fishing offences in the Peel-Harvey region in the past year.
The department said 985 offences had been detected in 2013/14 and there had been more since July.
Supervising Fisheries and Marine Officer Jay Tomkins said there had been a rise in the number of people exceeding bag limits and taking undersize crabs.
“I’d say [the number of offences] has gone up by about 30 per cent in the past year,” he said.
“It’s hard to give a number but it has gone up significantly.”
Mr Tomkins said more signs had been erected than usual this year to help keep people informed about the crab fishing closure.
“We had complaints last year about a lack of signage so we’ve put up more,” he said.
“There are about 30 signs along the Peel-Harvey Estuary including four at each bridge.”
The maximum fine for taking undersize crabs is $1000 or $5000 in court.
Guides are available online at fish.wa.gov.au.
