Artificial Reefballs put on Fish-Friendly Growth Spurt

Marine life is already flocking to artificial reefs just two months after divers began placing them in the Long Bay-Okura marine reserve, on Auckland's North Shore.

The trial project is the fulfilment of a dream for Long Bay College physics and science teacher Jonathan Jaffrey, who was selected for a Royal Society Teacher Fellowship this year and chose the creation of artificial reefs as a research topic.

Mr Jaffrey is using an American method, marine-grade concrete "reefballs" - hollow half-spheres weighing 250kg to 1000kg. They are towed into position with the help of flotation bladders and gently submerged.

He won resource consents and permission from the Department of Conservation to put the reefballs in the marine reserve - their first scientific trial in New Zealand.

Two reefs are being constructed, one in a zig-zag pattern about 20m long and the other in an octagon, to see which design best suits the conditions.

Mr Jaffrey says the reef trial is inside the reserve so that divers or fishers will not visit the reef and distort the research results.

"One of the driving reasons for creating marine reserves is so that we can do research on marine environments in a pristine condition.

"You cannot do meaningful research on what grows in the sea while you have people out their plundering it with whatever they happen to have to hand."

Mr Jaffrey says weeds have started to grow on the reefballs and they are being colonised by marine invertebrates and small fish.

"I'm over the moon at the amount of growth we have got. It is quite astonishing."

He has been trying different formulations with help from Firth Certified Concrete.

Gibbons Crib Walls has provided space and equipment for the project, and students from the Auckland University of Technology have also helped.

Reefballs are used overseas to repair tropical reefs damaged by hurricanes, says Mr Jaffrey.

He thinks they will be useful in New Zealand for controlling beach erosion by stopping sand from being washed away to sea.

They could also provide good snorkelling and diving spots, as well as being used to enhance fish stocks.

Mr Jaffrey hopes that after his research project reefballs will become an established way of creating artificial reefs in New Zealand.

NZ Herald 18/10/01