Not easy to keep fanworm out of port

Fanworm

Controlling the aquatic pest Mediterranean fanworm is likely to be a continuing struggle for Gisborne but results so far have been good, the District Council’s environmental planning and regulations committee was told.

Environmental and science manager Lois Easton said divers brought to Gisborne from Bay of Plenty found only one fanworm, which was encouraging.

The pest was introduced to the port in 2013, coming in on the hull of a fishing boat that spread it to other ports of the country before it was caught in Whangarei Harbour and later destroyed.

It was probable fanworm originally came into the country on boats from overseas that stopped at places like Auckland before moving around.

Fanworm filtered food out of 20 times the amount of water as a farmed mussel, so fanworm both smothered and starved them — which was a threat to aquaculture as well as natural populations of mussels and crayfish, she said. They produced arsenic, so had no predators.

Divers worked their way through the port, looking at all structures, checking every pile and vessel. The most recent check by divers found only one fanworm.

They were able to check the tidal area and were reasonably confident there was no population spreading.

“But that does lead to the conclusion we are seeing repeated reintroduction from vessels,” she said.

“That is the only reason we would still find fanworms.

One of the advantages in terms of vulnerability to marine pests was that the port was at the mouth of a quite a large freshwater river, so Japanese kelp established here for about 15 years did not grow that well.

“We do think that, again because of that estuarine freshwater environment, in Gisborne they are reaching sexual maturity later.

One of the great things about having only single finds was the likelihood of them finding another mate was quite low. They mated by releasing sperm and eggs into the water.

All fanworms found that were big enough to reproduce had been sent to NIWA and it was found that none of them had spawned, which was really great news but did raise the question of why they kept finding them here.

There was a technical term for the level of foul on a boat and under the regional plan, boats coming into our harbours must have a foul level of one or less.

If that was not adhered to, there would be huge colonies of all sorts of things coming into the district.

That could be hard to tell from shore, so when divers came in they checked the level of foul on boats in the marina once a year. The marina operators were very co-operative and followed a nationwide code.

This year was the first time a fanworm had been found on a boat here. Previous ones were on port structures. It was sent way for testing and its age and size made it likely that it came into Gisborne on the vessel.

The committee adopted a recommendation from Ms Easton that Gisborne join other councils in an inter-regional marine pathway. That would involve co-operation with other councils, such as Bay of Plenty, who provided the divers for Gisborne.

Controlling the aquatic pest Mediterranean fanworm is likely to be a continuing struggle for Gisborne but results so far have been good, the District Council’s environmental planning and regulations committee was told.

Environmental and science manager Lois Easton said divers brought to Gisborne from Bay of Plenty found only one fanworm, which was encouraging.

The pest was introduced to the port in 2013, coming in on the hull of a fishing boat that spread it to other ports of the country before it was caught in Whangarei Harbour and later destroyed.

It was probable fanworm originally came into the country on boats from overseas that stopped at places like Auckland before moving around.

Fanworm filtered food out of 20 times the amount of water as a farmed mussel, so fanworm both smothered and starved them — which was a threat to aquaculture as well as natural populations of mussels and crayfish, she said. They produced arsenic, so had no predators.

Divers worked their way through the port, looking at all structures, checking every pile and vessel. The most recent check by divers found only one fanworm.

They were able to check the tidal area and were reasonably confident there was no population spreading.

“But that does lead to the conclusion we are seeing repeated reintroduction from vessels,” she said.

“That is the only reason we would still find fanworms.

One of the advantages in terms of vulnerability to marine pests was that the port was at the mouth of a quite a large freshwater river, so Japanese kelp established here for about 15 years did not grow that well.

“We do think that, again because of that estuarine freshwater environment, in Gisborne they are reaching sexual maturity later.

One of the great things about having only single finds was the likelihood of them finding another mate was quite low. They mated by releasing sperm and eggs into the water.

All fanworms found that were big enough to reproduce had been sent to NIWA and it was found that none of them had spawned, which was really great news but did raise the question of why they kept finding them here.

There was a technical term for the level of foul on a boat and under the regional plan, boats coming into our harbours must have a foul level of one or less.

If that was not adhered to, there would be huge colonies of all sorts of things coming into the district.

That could be hard to tell from shore, so when divers came in they checked the level of foul on boats in the marina once a year. The marina operators were very co-operative and followed a nationwide code.

This year was the first time a fanworm had been found on a boat here. Previous ones were on port structures. It was sent way for testing and its age and size made it likely that it came into Gisborne on the vessel.

The committee adopted a recommendation from Ms Easton that Gisborne join other councils in an inter-regional marine pathway. That would involve co-operation with other councils, such as Bay of Plenty, who provided the divers for Gisborne.

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