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NIWA and Environment Southland have recently returned with stunning new footage of undersea sills in Dusky and Doubtful Sounds, brimming with sea life, corals and sponges. The footage was taken from a remote-operated vehicle (ROV), and is being used to assess 20 areas within Fiordland currently designated as anchoring sites for tourist cruise ships.
“The scientists were surprised with what is down there. It’s pretty amazing,” says NIWA’s Nelson Regional Manager Ken Grange. It’s believed the ROV footage has captured new species and previously undescribed habitats after only a week surveying Fiordland’s undersea sills.
“We know that the fiords are globally unique and have some of the highest marine diversity in New Zealand, but the discovery of these sill communities was outstanding. We can’t wait to get back and survey more of them,” says Grange.
“We found large areas of horny coral fans, rare and protected fragile red coral, sponges and sea pens. Large black coral trees, over a metre tall, were attached to the rocks and they provided shelter to large numbers of rock lobsters, while dense schools of fish, mainly butterfly perch, hovered above.”
“There were several dozens of things that are new to science: sponges, sea pens, corals, sea squirts and sea cucumbers. Prior to this trip, we didn’t know about these sill communities,” says Grange.
Ships’ anchors would be very destructive to such habitats. This year, 87 cruise ships will bring tourists to marvel at the spectacular scenery in Fiordland National Park. Next year there will be 90. Only a few of these ships drop anchor, but those that do can offload passengers in large numbers to sight-see in Zodiac boats.
In the past, Environment Southland and NIWA have scanned the Fiordland area using sonar to identify preferred areas where tourist cruise ships could anchor. Some of these areas include the sills that are now known to contain significant wildlife. Alternative anchoring sites will need to be identified.
The fiords were formed by glaciers some 20,000 years ago and are characterised by deep basins with one or more rocky sills that mark the seaward extent of the former glaciers. Some fiords have several sills along their length and, because they tend to be relatively shallow (some less than 50m), are potential anchoring sites. Cruise ships have to anchor in roughly 50 metres of water. The basins are up to 300 metres deep.
Some of the ROV footage was shown to the Fiordland Marine Guardians at their last meeting in late April. Their interest and support will assist NIWA in seeking additional funding to explore other sills throughout the fiords, and help manage these unique habitats.