Kina to the rescue. SAM McKNIGHT reports.
It is akin to a battle between good and evil – an invader against one of our own. Its outcome could hail a new era or dash fresh hopes.
No guns, no tanks, no missiles. The weapons in play are appetite versus a multiplying enemy set in a watery arena embedded in the ventricles of the heart of Fiordland.
It is a new mode of tackling the invasive Japanese-import undaria that has taken a determined hold at Sunday Cove in Breaksea Sound – using kina, or sea urchin, to eat it.
Thousands of the spiky depth-charges have been shipped to the cove with one mission, seek out and destroy the kelp, reinforcing the best efforts of wetsuit-clad divers who are taking the most uncomplicated of approaches – yanking them out.
The novel idea emerged in perhaps the most curious of circumstances, a meeting of minds between a passing kayaker stuck in Fiordland on his bid to circumnavigate New Zealand and divers on a surveying operation.
"Why not try kina?" the kayaker, Tim Taylor, asked.
The idea was discussed and the concept developed.
The sea creature, probably better known for its spot on menus rather than as a agent thrust into a biological war, is known for its ability to devour and destroy kelp forests, leaving behind a Somme-like wasteland known as a "kina barren".
It is that genocidal ability that the alliance between Environment Southland, the Ministry of Agriculture and Forestry, and Department of Conservation want, almost a scorched-earth approach in a localised area. The aim is to wipe out undaria.
If unchecked, undaria can be highly invasive and form dense stands, choking native plants and animal species of precious light and space.
The incursion is not the first in New Zealand, with undaria found in ports across the country, from Auckland to Bluff.
But its spread to Fiordland is a step too far, activating an immediate response first to stop it, then get rid of it.
Hence the new technique in the battle to control the pest since its discovery growing on a rope tethering a barge to the shoreline at Sunday Cove in April last year.
Ever since, the three agencies have been trying to keep undaria at bay through extraction, but data from the last few surveys show the population has been increasing as the new season's growth began. In February, 48 plants were found at Sunday Cove, including two mature plants; in March four more mature plants. The numbers kept climbing in April and May as the progeny of the mature plants developed – 13 in April and 253 in May.
Time was of the essence and, with a special permit awarded to the council by the Ministry of Fisheries to dispatch the kina, the operation, one of the longest undertaken, began on June 20.
It was a window of opportunity that could not be passed up, occurring at an important stage of the undaria life cycle.
Environment Southland biosecurity officer Tim Riding said it was a full-on operation to shift the kina from Saturday Cove to Sunday Cove.
Called in for the task were two skilled kina and paua free-divers, Rob Emmett and Kina Scollay, who worked at a staggering pace, pulling up between 50 and 80 kina on each breath.
Each kina-laden sack was quickly loaded on to a waiting dinghy, then to the main vessel, the Department of Conservation boat Southern Winds, for a short trip around the corner to their 1.5-hectare hunting ground, placed into the water and marshalled into position by another set of divers.
The frantic pace did not let up and, in Mr Riding's estimate, 20,000 to 25,000 kina were snared and moved in about seven hours.
Since then, the kina have been left to weave their magic.
Mr Riding's optimism is based on more than mere hope.
He is expecting success. His confidence is backed by field experiments that have already shown the beauty of kina as a tool.
Kina not only wiped out the undaria plants, it is also suspected they devour the microscopic stages, nipping future growth in the bud.
Where kina were found, there was no undaria; where kina was absent, there were up to 100 new plants, he says.
MAF pests and pathways manager John Randall says although using biological control in a terrestrial environment is relatively common, that same approach in the marine context is new and exciting territory – if it works.
There are plenty of questions that remain unanswered and should be revealed in followup surveys. Could kina, being a mobile species, be relied on to stay in the desired area? What would happen once they had depleted the food source?
As a technique, it was an attractive one, by using a species that could be found nearby and not introducing another foreign organism to do the work.
If the project was successful, it could be an effective tool for others. So the waiting game to determine the success or otherwise of the operation will loom large in the minds of those at the forefront of the operation.
D-Day for the next survey is August 1 and, following that, a close eye will be kept on the exercise, with a more intensive monitoring regime.
That would address the possibility of any effects caused by the kina, including whether their barrens impacted on other species that fell outside the target species.
The operation could have harvested up to 100,000 kina for the drop, but the decision was made to take a conservative approach, using only a quarter of the permitted number.
Kina numbers would also be controlled from predation by blue cod, crayfish and moki, all of which have a taste for the species.
"But the hope is before the kina get hammered by their natural predators, they'll do their job first."
- The Southland Times