Australia's government is staring down the barrel of losing its majority.

The High Court will decide today whether the dual New Zealand citizenship of Deputy PM Barnaby Joyce means he's unfit to remain in parliament.

If the court rules him out of Canberra then the coalition loses its one-seat majority.

Australia correspondent, Murray Olds told Mike Hosking his supporters say the constitution is a 100 year-old document, which needs updating.

"Others are saying well bugger Barnaby Joyce, if he didn't know he should have. Let's not have a bi-election, let's just go the person who came second and put them in parliament. That would not suit Malcolm Turnbull."

LISTEN ABOVE AS MURRAY OLDS SPEAKS WITH MIKE HOSKING

Green MP Julie Anne Genter expects the Kermadec sanctuary to go ahead under the incoming Government.

The bill to establish the world's largest marine reserve was put on hold last year due to legal objections that it overrode Maori treaty rights.

There have been fears the bill could be scrapped in the Labour-New Zealand First coalition agreement.

Ms Genter said more consultation is key to getting a good deal for everyone.

"You don't just go out there and bowl people over and put stuff up. That's not a good way to run a country, you can get good environmental outcomes and make sure everyone is on board."

It's hoped someone will come forward with information about a two-year-old girl who disappeared near Queenstown 25 years ago this month.

Amber-Lee Cruickshank went missing from the beach at Kingston - a town at the southern end of Lake Wakatipu.

READ MORE: New podcast delves into chilling cold case

Warwick Walker was the first detective to work on the case.

He told Mike Hosking there's a chance remains will be found somewhere accidentally but says generally in these cases, someone knows what's going on.

"Sometimes a change if allegiance over time can mean that somebody will come forward and that's really what I think we have to hope for now."

The Herald has just released a six part podcast on the case called 'Chasing Ghosts'.

LISTEN ABOVE AS WARWICK WALKER SPEAKS WITH MIKE HOSKING

Incoming Finance Minister Grant Robertson says he's optimistic about the economy, despite Winston Peters forecasting a slowdown.

Mr Robertson says economists have mixed views on the short term future of the economy.

But he says there are signs growth is beginning to tail off.

He said New Zealand's in a position to deal with whatever economic slowdown there might be.

"But we've got to be mindful that some of the conditions may change - like pop gowth and s booming housing market - might change, and we've got to be ready for that."

LISTEN ABOVE AS GRANT ROBERTSON SPEAKS WITH MIKE HOSKING

Peter Dunne says some New Zealand First MPs won't be good ministers.

The former United Future leader thinks overall, Jacinda Ardern has done a good job selecting her cabinet.

But he told Mike Hosking he has serious doubts about Labour's coalition partners.

"I think the Green Ministers will be okay. I have real worries about some of the New Zealand First people because frankly as a group they're not up to it."

Dunne has had his own issues as a Minister, resigning in 2013 over what he described as lapses of judgement.

He was reinstated the following year.

LISTEN ABOVE AS PETER DUNNE SPEAKS WITH MIKE HOSKING

Male salmon appear to have a clever way to get ahead of their breeding rivals.

A Canterbury University study has found chinook salmon can adjust their sperm's swimming speed, when competing with a rival to reproduce.

PhD student Michael Bartlett says the adjustment of sperm velocity alters male reproductive success and therefore fitness.

He said it's probably not a conscious decision by the fish.

"It's a physiological response by the fish in response to those cute signals from various things."

Bartlett is continuing the study in an effort to try to learn more about human fertility.

LISTEN ABOVE AS MICHAEL BARTLETT SPEAKS WITH MIKE HOSKING

National's Finance Minister, Steven Joyce and Labour MP, Stuart Nash join Mike Hosking for Politics Wednesday.

Party campaign manager and outgoing Finance Minister, Steven Joyce told Mike Hosking they'll be putting up a strong contest over the new government's policy direction.

He said it's not like they were thrown into the corner by the public, they're actually the largest party in Parliament by 10 seats.

Mr Joyce predicts they'll spend a lot of time debating how the government's reforms will affect small businesses.

LISTEN ABOVE AS STEVEN JOYCE AND STUART NASH SPEAK WITH MIKE HOSKING

School principals say the new government won't fix the education system without addressing underlying issues.

UNESCO research shows teachers are under increasing pressure to be de facto counsellors, data analysts and social workers.

Auckland Primary Principals Association president, Kevin Bush said it gets in the way of teaching.

He told Mike Hosking teachers are on the frontline of a wide range of social issues that need to be addressed.

"We've got behavioural challenges. We've got P babies, fetal alcohol syndrome babies. We see the effects of some of those things."

He said the new government needs to stress parental responsibility on issues like obesity.

"We don't feed the children. The parents feed the children and it's what they're feeding them, it's getting them off to sport, it's being active with them outside.

LISTEN ABOVE AS KEVIN BUSH SPEAKS WITH MIKE HOSKING

A business leader says it's unlikely Winston Peters will get his wish for Auckland Port operations to move north.

Auckland Chamber of Commerce chief executive, Michael Barnett said a port in Auckland is preferable, and moving it north would cost billions.

He told Mike Hosking Northport has just 20 per cent of the berthage of Auckland, and it's moving goods further away from the final destination.

"They'll go through a process but if you just look a t the numbers I've given you there, the answer is it probably won't happen."

The Government has agreed to a feasibility study on moving the port.

LISTEN ABOVE AS MICHAEL BARNETT SPEAKS WITH MIKE HOSKING

It's being suggested a $20 minimum wage in 2021, is the same as a $17.50 minimum wage today.

Economist, Dr Eric Crampton of the New Zealand Initiative think tank, told Mike Hosking there are already good numbers from MBIE around the effects of minimum wage increases.

He said if today's minimum wage was $17.50, it would cost jobs and the country.

"That would be about 15,000 fewer jobs than we would otherwise have and a net cost to the government of about $125 million."

LISTEN ABOVE AS ERIC CRAMPTON SPEAKS WITH MIKE HOSKING