There is still no end in sight for the ban on harvesting cockles from the Whangateau Harbour, now in its 10th year, experts say.
The former Fisheries Ministry enforced the ban in 2009, at the request of locals, after 60 per cent of cockles were decimated by a rare combination of parasite and bacterial infection.
The harbour was last surveyed by Fisheries Management with the Ministry of Primary Industries during the summer of 2017/18. The survey showed overall numbers had increased to 852 million cockles, up from 742 million cockles in 2015/16, but the number of mature cockles of at least 30mm in length had decreased.
Fisheries Management director Stuart Anderson says while it is positive that the overall population has increased, he does not consider that the health of the Whangateau cockle population has returned to levels that would indicate harvesting should resume.
“We will continue to monitor the shellfish populations and any future decision to reopen Whangateau to cockle and pipi harvesting will be made after public consultation,” he says.
Marine biologist Dr Karen Tricklebank surveys the cockle population twice a year with Mahurangi College sustainability education students.
Her data is consistent with Fish Management, showing that the number of mature cockles greater than 30mm has not increased in the last 10 years.
She says there is no clear answer about why the larger cockles have not returned.
“We would have expected the cockles to grow to 30mm within three to six years,” Dr Tricklebank says.
“Perhaps they are dying before they get to a certain size, or maybe environmental conditions have changed and just don’t support growth to a large size.”
She says studies have shown that cockles need to be at least 18mm to reproduce and are able to produce exponentially more eggs the larger they grow. She says that because people tend to collect larger cockles when they are harvesting, the ban ought to stay in place.
The monitoring programme was founded by the late Dr Roger Grace in 2006.