Every April, thousands of the hoary-backed spider crabs move from the open ocean into Port Phillip Bay and congregate before their annual winter moult.
This phenomenon reached a global audience when it was featured on David Attenborough’s Blue Planet documentary series last year, drawing new visitors to the Mornington Peninsula.
But it also made spider crabs a target for recreational fishers.
And despite early warnings this year from environmentalists, over the June long weekend the Rye Pier was crowded with people hauling hundreds of crabs out of the water.
The pier became so full that it was closed by police, due to social-distancing concerns.
And after the three days the sea floor was left littered with rubbish, says recreational diver PT Hirschfield, the founder of the Spider Crabs Melbourne Facebook group.
The fishers numbered in the hundreds, and she estimates “many thousands” of crabs were taken in a short period of time. Previously, it was estimated about 8000 to 10,000 crabs had congregated near the pier.
“They were pulling the crab pots up through the piles of aggregated crabs, scraping along the fragile sponge walls on the pylons, and throwing chicken carcasses and cable ties down when they were finished,” Ms Hirschfield says.
One diver counted 80 chicken carcasses, and noted a number of sharks under the pier.
Ms Hirschfield said it was important not to be alarmist about sharks, but noted it was rare to have hundreds of people fishing from a pier, with large numbers of marine animals, carcasses strewn as bait and divers in the same area.
When Ms Hirschfield returned to the water after the long weekend, she noted there were fewer than 200 crabs in the vicinity.
Usually crabs would remain in the area for a fortnight after moulting to allow their new shells to harden, but when she dived there were very few left in the area, she says. Divers have been removing the chicken carcasses.
Victorian Fisheries Authority head Travis Dowling said the authority had been closely monitoring spider crab fishing and compliance with regulations had been high. He said there was no evidence of over fishing.
“There are lots of giant spider crabs, enough for divers to view and recreational fishers to enjoy,” Mr Dowling said. “There is also no commercial fishery for the crabs in Port Phillip, which adds further protection.”
In an Australian first, the authority will tag spider crabs using satellite technology to help understand their movements. It will also work with divers and fishers to collect shell moults and catch information.
Ms Hirschfield and the Victorian National Parks Association urged all parties involved to consider a “no-catch” policy around Rye Pier while crabs were moulting.
Miki Perkins is a senior journalist and Environment Reporter at The Age.