WA police have confirmed two men are in custody, after 200 kilograms of shark heads were dumped outside the WA Fisheries Minister Jackie Jarvis's office in protest of the upcoming ban on demersal fishing.

The heads of multiple shark species along with a message inscribed on fishing overalls were found outside the office in Margaret River, 270 kilometres south of Perth.

The demonstration comes just three days before the permanent ban of commercial demersal fishing comes into effect along 900 kilometres of the West Coast from Kalbarri to Augusta.

Overalls were also found outside the ministers office.  (ABC South West WA: Madigan Landry )

Bunbury recreational fisher Mason Jones was one of the four people who organised the protest.

As well as carting in a mixture of bronze whaler, wobbegong, hammerhead and whiskery shark heads, he said the group brought wet weather clothing worn on commercial fishing boats as part of the demonstration.

"Jackie Jarvis got a little package delivered to her just to start off the end of the year, to let her know how she ended the many careers of fisherman and small businesses," Mr Jones said.

"She left them quite dirty so, she was left quite dirty.

Mason Jones says he wanted to leave a "dirty" surprise for the WA Fisheries minister. (ABC South West WA : Jacqueline Lynch)

"We also left a set of overalls that were kindly donated from some commercial guys," he said.

"On there we had written 'to Jackie from all fishers' and that's just to let her know that we're uniting."

Jarvis defends decision

A spokesperson for the WA Fisheries Minister Jackie Jarvis said the decision to ban commercial fishing of the species was not made lightly.

Minister for Fisheries Jackie Jarvis says the decision came after extensive consultation. (ABC News: Courtney Withers)

"These reforms follow extensive, respectful and inclusive consultation with industry and the community, including the Fishing Futures Forum," they said.