More than 40 marine pests have been identified by experts as lurking in the waters of Tauranga Harbour at any one time.

Asian paddle crabs, sea squirts, and Mediterranean fan worms are among the contingent of introduced or invasive species that could have massive implications for the region's infrastructure.

Yet, according to Dr Kaeden Leonard, most people are unaware of the dangers below the water's surface.

That needed to change, he said.

Advertisement

"We definitely should focus our attention more on marine life. But that said, New Zealand is one of the countries that's really leading the way in biosecurity."

Leonard is a biosecurity specialist who heads the University of Waikato's biosecurity and surveillance partnership with the Bay of Plenty Regional Council.

Divers are in the harbour every second day checking under boats, pontoons and piers for unwelcome invasive species.

The team is also part of the newly formed Tauranga Moana Biosecurity Capital, which officially launches today as part of a wider symposium this week on biosecurity.

"There definitely needs to be a lot more education out there with regards to how we could be affected. It's not just the marine industry. It's all of us," Leonard said.

Invasive pests could not only wipe out some species but could create additional environmental issues, job losses and loss of business if left unchecked, he said.

There were more than 40 known marine pests in Tauranga waters but Leonard said it was hard to give a specific number due to the classification of some species.

"Fortunately New Zealand has been quite lucky and we've remained free from species that have impacted other countries."

The Mediterranian fan worm can be seen established on the hull of a boat, both in and out of the water. Photo/Bay of Plenty Regional Council/University of Waikato.
The Mediterranian fan worm can be seen established on the hull of a boat, both in and out of the water. Photo/Bay of Plenty Regional Council/University of Waikato.

Leonard said the Mediterranean fan worm, for example, severely impacted the aquaculture industry and has already wreaked havoc on mussel farms in the north.

"These species have an ability to out-compete our native species," he said.

The aggressive Asian paddle crab can have as many as 400,000 eggs and the ability to reproduce "a number of times throughout their lifetime".

The regional council has this year been placing traps for the crabs around the harbour in an effort to try to prevent the species from becoming a major problem.

Leonard is away this week but Professor Chris Battershill will discuss marine invaders at the symposium.

Tauranga Moana Biosecurity Capital's Andrew Harrison said the group formed to pool its expertise and resources "for the sake of the environment, our taonga, our economy".

The group comprises of 19 Western Bay and Tauranga organisations from the education, horticulture, civic and business sectors, including all three councils and the Port of Tauranga.

Some of the weird and not-so-wonderful marine pests also include:

- Droplet tunicate which forms large colonies and is generally found in muddy bottomed tidal habitats and structures like wharf piles. It can smother beaches, rocks and tide-pools and displace native species and has become more prolific in Northland.
- The Asian date mussel, also known as Asian mussel or bag mussel, is a small saltwater mussel that can alter seafloor habitats.
- Wakame Undaria is an Asian kelp that can form dense forests in sheltered reef areas, resulting in competition for light and space.
- The Asian clam hasn't been found in New Zealand yet but is a significant biosecurity threat as it can occur in high densities such as over 25,000 per square metre.
- Source NIWA