Dave Cade: On the draining of Lake Rotomanu in the fight against the invasive gold clams

A New Plymouth lake is being drained in an effort to stop invasive clams. 

Lake Rotomanu's been closed to motorised watercraft since the gold clams were found there last month, marking the first discovery of the species outside of the Waikato River. 

The lake's outlet was opened yesterday, and it will take about four days to drain completely. 

Dave Cade told Kerre Woodham it’s the worst biosecurity threat to New Zealand’s freshwater that the country’s ever faced. 

He says the clams reproduce asexually, and they’ll smother the bottom of lakes, smothering native organisms and clogging hydro stations.  

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Episode Transcript

Speaker 1 (00:06):
You're listening to the Kerry Wood and Morning's podcast from
News Talks.

Speaker 2 (00:10):
He'd be yesterday when we were talking about the gold
clams and the draining of the lake in Taranaki. Didn'm
o Dave come on, but too late for us to
take him. So he joins us now and you are
hot on the gold clams.

Speaker 3 (00:24):
Dave, absolutely, Carrie, we are hot to trot on it.

Speaker 2 (00:29):
Tell me about them. Let this be another learning right.

Speaker 3 (00:33):
They're an Asian clan that has been spread around the world.
We don't know how we're into New Zealand or from
what country. They were found on the White Kettow River
about nearly two and a half years ago. They think
they've been there for a couple of years. We controlled
it in the White Kettow River and kicked in there
until they suddenly shown up in Lake rod and Armon.

Speaker 2 (00:52):
And that's the first time they've popped up outside of
the White Kettle River.

Speaker 3 (00:56):
Wykeatdow River here. So you've got Denmo horn, lord alligator
weed are serious threats. They can't hold a candle to
these clams. This is the worst bice security threat to
New Zealand's bridge water we've ever faced. Why one, they
can breed seven four or five six, seven hundred times
a day and they don't need Num and Dad. They

(01:16):
can do it on their own. So they'll just smother
the bottom of lakes. Just incredible infestations, which doesn't do
anything for the Khaki, the native muscles and all the
rest of it. There are a massive threat to our
hydro power stations because they'll get it there and clock
it up. And the other one that's really starting to
hit and I've never seen this before carry is the

(01:37):
lockdown and the loss of access, enjoyment and freedom around
around the north Island. Lake Okataina has big restrictions over
what you can do on what you can't. There's controlled
area notices on the way kadow River Lake wrote a
Namu shut Lake rote Akari down the road proportion. The
Northern Regional Council and the EWE and US are up

(01:58):
lined up against kai Pro District Council wanting to shut
motorized craft on Kaiwi Lakes. We've got lots of accessing
big time over these things. And the reason is is
because we cannot get people to clean their gear as
they move gerry.

Speaker 2 (02:12):
Would it be easier if the gunk was easier to
see because as I understand it, it's a thin and
visible mucus, which makes.

Speaker 3 (02:19):
Microeh it's microscopic. So people look at the clams and
the photos and if it were one of the things
they go is can I eat them? Well, no, they can't.
One is because they're filter feeders, and who'd want to
eat anything that's filtering with like at a river. Second,
is there an unwanted organism under the biosecurity acts. You're
going to get done if you shift them. But the
big problem is it's what they call a spat, which

(02:40):
is the slimy stuff in the juvenile stage, and it's microscopic.
So the idea of gredging or anything to get rid
of something microscopic out of a river, the size of the
white at, it's just not there. But it all comes
back to that check clean dry. We know that birds
don't move them, Okay, we know that they can't moon

(03:02):
walk down state our way one like Michael Jackson and
jumping into the lake. It has to beat human controlled
activity of absorbent type materials like wetsuits, boats, ballace, tanks
on things like that. But these things are really going
to hit us hard and we have thrown as you know.
I mean I checked your shoes at the Tussett reversed
many many years ago. Oh yes, and your mum. We

(03:28):
have thrown everything at the check Clean Dry program for
eighteen to twenty years. And I mean great organizations like
Tiara or Lakes Trust and Rod and all the other
and we just cannot get people to clean their gear.
And it's just it's an absolute tragedy. But that's the
real problem. And I had a conversation with the Governor

(03:50):
General last year. I was privileged toing and she asked
me how the fresh water fight was going, and I said,
not good. I see the most bloats in youw Zealand.
I'm more worried about where the boat and Barrett's going
to start the game. I'll come off the bench and
they are about the body security of our country. Yeah,
that's true, Jesus.

Speaker 2 (04:06):
Unless you can see it, it's very hard to take
it seriously to battle it.

Speaker 3 (04:11):
It is. It is. But what's going to happen is
it's the loss of access. That's the one that's going
to at home. I mean they jumping up and down
in Taranaki at the mountain a moment like rolling an
army and things that no one's really getting stuck into.
Who shifted them there? If someone hadn't shifted them out
of the white at a river down to Taranaki, there
wouldn't been the need to drain like running on it.

Speaker 2 (04:30):
But would they necessarily have known that they were.

Speaker 3 (04:36):
Clean dry when you move waterway, Garrie? I mean that
has been but that has been the message around New
Zealand for twenty years. You don't wait till you know
something's there. Your check clean dry every time you move that.

Speaker 2 (04:51):
Not everybody's going to do one hundred percent check clean dry,
are they? They're like they might think it's good enough,
but it hasn't been it. I don't necessarily think it
will be intentional, will it?

Speaker 3 (05:02):
Well? Probably not. No, we haven't comployed with the program,
you know, and and we're out there and the other
thing is, of course is the other thing is that
we're slim on the ground. I mean, my my area
is a horizon for regional Accounts Advocate is to cover
the buyer security from townman Nuiy to Fonglan NUIs cross

(05:22):
to Parmers in the north up to and back to
towneran Nui part time. I'm own Now. I might be good,
it might be pretty good, but I ain't superman, are you? Okay?
And that's the problem with tooth in on the ground.
So while I am, for instance, in National Park wy
Marino on at Knights talking to all the freedom campers
who are moving around all over New Zealand, Okay, there's

(05:45):
no one else in any of that whole area that's
doing any by security work because anybody funding for them. Yeah,
Turans is the wonderful thing, but you know, you've got
to you've got to look after what they actually want
to come and see. You know, we're We're a case
where a guy called Andrew Dewing runs a B and
B an ophono and we had some Korean people that

(06:05):
all some gold clams out of the Waycatto River and
went for a ride and stopped at his place in
o Fongo south of Tamanui and put them on the
counter and said what are these? And he just took
them straight off and straight off and rang me and
see what are these? I said, So we got at
the NPI they confirmed they were gold clams, and they
went after this couple around New Zealand soil. They got them,

(06:27):
and see where have you been and what have you done?
Now it's as simple as that.

Speaker 2 (06:31):
Well simple and as you know, having to be an
all play. Do you feel a bit like King Canute,
like trying to stop the tide of golden clams from
crashing in?

Speaker 3 (06:41):
Here? We do? We just stretched beyond belief.

Speaker 2 (06:44):
Okay, somebody says, did it my Dave as an absolute legend,
But then more pertinently says, get this guy to say,
what is the bare minimum needed to clean your gear
to a safety standard?

Speaker 3 (06:56):
The key one, if you ken, if you can plan it,
the key one is to dry them, dry anything out
till it's touch dry, and then wait another forty eight
hours and your.

Speaker 2 (07:05):
Fine before you can move.

Speaker 3 (07:08):
Yeah. Yeah, if you want to do it faster than that,
and you've got a pair of fishing waiters, it's fifty
five degrees sea hot water for five minutes, or it's
it's two percent bleach for an hour. Now. See, we
could kill Denimo with ten percent solution and dish washing liquid,
but these things we need fifty five degrees. See, they're
very hard to kill. They're very hard to kill. And

(07:30):
that's one of the things to any absorbent material like
wet suits or anything like this. That the simplest thing
would be to do would just be to plan your
trips so you're not moving around over the place. And
the second thing is it would be to dry it out.
That's the simplest way. But again it takes touch dry
plus forty eight hours. Right.

Speaker 2 (07:49):
That's quite complicated, isn't it?

Speaker 3 (07:51):
Like quite? I mean we run the NPI all the
time saying get your scientists together. I mean if I
if I meet somebody who's come out of the Tomrera
River and they've hopped a close to the Focker Papa
River on the same day and they haven't cleaned their
get what am I going to do on the Focker
Papa rank. I don't have fifty five degrees sea hot
water and the thing that I don't have two percent
bleach and they're not going to stand here for an
hour in it. We've got some real problems. But the

(08:15):
key thing comes back to the compliance to the check
Clan Drive program. Now the road for instance, and I'll
give you an example, the road of Relakes. The boys
over there Tiara or Lakes Trust and now they're doing
a fantastic job. Now. They had a self certification system
program going on the Road of Relakes, so you'd go
on there and say your name's Carrie Wood and this
is your boat, where you've been, et cetera, et cetera,
and you've put the certificate on the dashboarder you can't

(08:38):
After three years they're running on twenty four percent compliance,
which means seventy six percent of people using the Road
of Relakes were not complying. That was why when the
Gold Clan threat came along, the restrictions went on Lake Okatina. Basically,
we've got to look after this. We just I mean,
you've got so many people in Lake's Tiara A Trust.

(08:58):
They're probably the hottest group for freshwater buy security in
New Zealand. They're throwing everything at it and they can't
get the compliance above fourcusing, Well.

Speaker 2 (09:08):
It's on us, isn't it.

Speaker 3 (09:09):
Dave.

Speaker 2 (09:09):
Thank you very much for your time. As always, For.

Speaker 1 (09:12):
More from Kerry Wood and Mornings, listen live to news Talks.
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