The changes shorten the season by a month with a late start, as well as adjusting the size of crays that can be caught and limiting the catch.

Fisheries NSW executive director Dr Geoff Allan said habitat degradation and modification and blackwater events after flooding had taken a toll on the iconic native species.

NSW Fisheries’ scientific committee had called for the crayfish to be listed as being vulnerable with far fewer of them, especially in the lower reaches of the Murray and Murrumbidgee rivers.

“Recreational fishing does not appear to be a primary cause of decline but it is important we manage recreational fishing pressure to assist species recovery,” he said.

Taking crayfish in NSW will be allowed in only two specified areas — the Murrumbidgee between Gundagai and Berembed Weir, near Ganmain, and the Murray between 130 metres downstream of Lake Hume and the Newell Highway road bridge at Tocumwal.

The season opens on June 1 rather than May 1 to protect pre-spawning females.

The minimum size has been lifted to 10 centimetres from the rear of the ear socket to the centre rear of the carapace.

A maximum size of 12 centimetres has been introduced to ensure females reach sexual maturity and large crayfish are protected.

The daily bag limit has been reduced from five to two and the possession limit cut from 10 to four.

Dr Allan said the rules were effective immediately making it an offence to take crayfish next month.

“All other rules continue including a prohibition on berried females or removing heads, tails or claws in, on, or adjacent to waters,” Dr Allan said.

He said the rules would inconvenience those fishers in south-west NSW and Victoria who had planned to fish for crays in the Murray and Murrumbidgee next month.

“Fishers must ensure they know the rules because fisheries officers will be out in force to ensure the new arrangements are followed.”

Up to five hoop nets a person can be used where permitted with the letters “HN” and user’s name and address on the float.