Crayfish 'functionally extinct' in the Hauraki Gulf
An overhaul of crayfish management is being called for as crayfish numbers hit an all time low.
Crayfish numbers are so low they are no longer contributing to the ecology of the Hauraki Gulf and are "functionally extinct."
That's the view of director of fresh research marine ecology consultancy company eCoast Dr Tim Haggitt, after new monitoring in and near three marine reserves in the gulf show numbers continue to plummet.
There was an outcry earlier this year when ongoing research done in 2014 for Department of Conservation showed fish and crayfish stock at the popular Goat Island Marine Reserve in Leigh was lower than when the reserve was first established 40 years ago.
Crayfish were hardest hit, being taken by fishers as they feed on shellfish beds outside the reserve also leaving vulnerable youngsters unprotected from predatory fish.
Now Haggitt, along with senior lecturer in marine sciences at the University of Auckland, Dr Nick Shears, says crayfish numbers both inside and outside the Leigh reserve have dropped a further 25 percent in just two years.
While monitoring in the reserves is the focus, they also keep track of crayfish at sites outside the reserves for comparison. This shows crayfish numbers are also continuing to drop outside.
Surveys are done in autumn-early winter with crayfish numbers shown as average per 500m2 unit area with the same sites sampled each time.
At spots around the Leigh coastline and off Kawau Island in 1995 there were 10 crayfish per unit areas compared to 40 crayfish per unit area inside the reserve.
The lastest data works out at 0.5 crayfish per unit areas outside, and 10 inside the reserve.
"Current Leigh reserve crayfish levels are less than that recorded outside the reserve in 1995," Haggitt says.
But with crayfish numbers also falling inside and outside marine reserves at Tawharanui and across the other side of the Hauraki Gulf Marine Park at Hahei on the Coromandel there is a much bigger problem, they say.
The wider CRA2 fishery is in trouble, Haggitt says.
"There is clearly a need to do something about extending these reserves to offer greater protection for crayfish but also a drastic need for management action at a larger scale that will allow the stock in the wider fishery to rebuild," he says.
CRA2 covers from Waipu and East Cape including the Hauraki Gulf and Bay of Plenty.
In 2014, concerns over the fishery saw total allowable catch for commercial fishers reduce by 36 tonne to 200 tonnes
Estimated recreational take of 140 tonne remained the same as did customary take of 16.5 tonne.
Haggitt now has data going back 20 years for some sites outside the three reserves, but this isn't currently being used by the Ministry of Primary Industry in assessments to set quotas.
Haggitt would like to see this change along with smaller quota management areas.
"The fisheries management areas are too big. They need to be smaller, with more local based management," he says.
While crayfish larvae can be found off the Wairapapa coast in CRA4 every year, in the Hauraki Gulf they seem to come in "pulses" every 6-7 years.
Numbers in the gulf are now so low the population could crash, they say.
Crayfish are historically top predators on the reefs. They also help to keep sea urchins (kina) in check and stop over-grazing once abundant kelp forests. The crays are now virtually absent and functionally extinct in the Gulf, Haggitt says.
Reefs and shellfish beds in their range need to be protected to keep them safe to breed, and just contribute as they are meant to, he says.
Proposals have been made to Sea Change - Tai Timu Tai Pari marine spatial plan for the Hauraki Gulf, expected to be released by the end of this year, to extend the Leigh marine reserve out to 3 kilometres. Similar extensions are sought at Tawharanui and Hahei with more Marine Protected Area's generally called for.
Regardless of the Sea Change outcome Haggitt and Shears say crayfish management has to change.