Possible solution for harbour

FINDING SOLUTIONS: Research diver Joe Burke and his wife, marine scientist Kura Paul-Burke, are working on a joint project to save the mussels in the Ohiwa Harbour. File photo

RESEARCHERS looking into Ohiwa Harbour’s declining mussel population have come up with a programme they believe will bring a solution.

Joe Burke and marine ecologist Kura Paul-Burke,  have been working on the Niwa and Bay of Plenty Regional Council joint project looking at solving the issue.

“Over the last 10 years, we’ve seen the mussel population drop dramatically.

“Over that time, we’ve noticed huge numbers of sea stars consuming the mussels,” Mrs Paul-Burke said.

“It’s all about balance and the balance in our harbour is not well.”
Mussels are a keystone species and they help keep the harbour bottom clear of debris.
“We need mussels on the bottom because they create hard surfaces for other species,” she said.
“They create biodiversity.”

Silt at the bottom of Ohiwa harbour

The researchers said though there was no guarantee the solution would work, they used the best information they could gather to find an answer.

“We’re crossing our fingers and saying we’re having a go.

“We don’t know if the answer is right but with the community effort, we’re hopeful,” Mrs Paul-Burke said.

The research has multiple aspects that need to succeed before they can claim a successful result.

Mrs Paul-Burke said their observations had sparked four questions.

“With the decimation of the mussel population can we relocate mussels back to the bottom of the harbour; will they reattach to the bottom; and if so – will they survive, and will they (procreate),” she said.

“Can the population stay on the bottom and rejuvenate itself.”

They are using both traditional Maori lines and modern western lines to research the issue.

“So, we have a Maori or indigenous perspective alongside western science perspective.

“We’re just trying to figure out what is the best material to use to assist the mussels and the best way to go about it,” she said.

“We have the traditional and western lines and we’re hoping to catch natural Ohiwa harbour mussels on that.

“On the bottom, we have cages made of metal and plastic and cages made out of natural resources,” Mr Burke said.

Once on the bottom, mussels still have another issue, predation.

“If we put the mussels on the bottom can we keep the sea stars away from them long enough for them to go through the cycle.

“The predation of sea stars on mussels is intense,” Mrs Paul-Burke said.

Large quantities of sea stars, below right, make it difficult for the mussels to survive.

If they can keep mussel predation to a minimum while also allowing other bivalves to establish in the harbour, they can re-establish the harbour’s equilibrium.

“Sea stars keep the balance in the harbour by eating mussels. If you have too many mussels they can take over and dominate the bottom so you can’t have pipi or other species,” Mr Burke said.

“Our project’s field experiments will end about this time next year. That will give us time to analyse it all and make recommendations.”