Crayfish bounce back in marine reserve

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Recent underwater surveys of the Tonga Island Marine Reserve are revealing the benefits of marine protection.

The 1835ha reserve, off the Abel Tasman coastline, has been a fishing-free zone since its creation in 1992, and is now being surveyed to provide detailed scientific information on changes that have been taking place since then.

The surveys, funded by the Department of Conservation and undertaken by the National Institute of Water and Atmospheric Research (NIWA) and Davidson Environmental, have found large increases in crayfish numbers within the reserve.

NIWA’s Regional Manager, Ken Grange, said that one count over the past two weeks indicated that crayfish numbers were nine times higher within the reserve than outside the reserve.

Researchers noted that many of the crayfish, particularly the females, had moulted their old shells and one was seen with eggs. "This shows that marine reserves really help the population to recover by providing a safe haven for animals during their breeding season."

Dr Grange said the survey also involved tagging crayfish to follow their movements. "This work is only possible within the marine reserve, as there are just far too few crayfish outside the reserve to find and tag.

"The crayfish inside the reserve are also beginning to behave differently. They do not hide in the back of crevices, which makes the tagging operation far easier."

He said the tagged crayfish would be followed over the next few months to see whether they remain inside the reserve after breeding. This information will help the Department of Conservation determine how big an area needs to be set aside for a marine reserve to be effective, and can be applied when future proposals for marine reserves are being considered.

The Department of Conservation’s Motueka Area Manager, Colin Wishart, said the results showed the benefits of marine protection.

"If this recovery of marine life continues, it will benefit the reserve’s marine environment and tourism potential, and the fishing elsewhere along the coastline."

He said the vast majority of fishers strongly supported the Tonga Island Marine Reserve, and hoped this would continue. "The department will also continue to undertake regular patrols of the reserve and, with the added vigilance from commercial boat operators, we are confident that compliance will remain high."

Under the Marine Reserves Act, all marine life within a marine reserve is protected, with penalties for illegal fishing now up to $250,000.

Research subject: Marine Invertebrates
 

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Archived on 9 April 2019