There were a few nervous moments watching a giant piece of pioneering equipment go over the side of NIWA's new research vessel for the first time, but this game-changing marine science tool is a winner.
The ability for scientists to see what's on the sea floor just got a whole lot brighter with the invention of an underwater multiple-camera system - and some ingenious thinking - at the National Institute of Water and Atmospheric Research (NIWA).
The system, known as SwathCam, was the idea of NIWA marine ecologist Dr Mark Morrison and takes advantage of a new fibre optic cable installed on NIWA's recently commissioned research vessel Kaharoa II. SwathCam is essentially a nine-metre metal frame fitted with five downward-facing video cameras - and one forward-facing one - and an array of extremely strong lights to provide crystal-clear visibility in the dark depths of the ocean.
Suspended from Kaharoa II, SwathCam is towed through the water about two to three metres off the seabed, sending high-resolution live video back on board for
viewing in real time.
Most of NIWA's current imaging systems are fitted with single cameras with relatively narrow fields of view - the SwathCam provides up to 10 times that ability, both at fine spatial scales (seeing how individuals of different species associate with each other and their habitats) and broader spatial scales (how many fish are present in an area, how are they distributed across different habitats).
For Dr Morrison, this is a game changer, not only for estimating fish species abundances and sizes, but also in understanding what seafloor habitats are present and how fish interact with them.
"We can now get a lot more information when surveying for the same effort and money, with the much higher spatial extent of the imagery. You can also use the cameras seamlessly over reefs and protected or vulnerable seafloors you really don't want to damage. It is a really good way of looking at things like marine reserves.
"The more we can measure, the stronger the data support for statistics and modelling, and the greaterthe new knowledge gains.
"By using this camera system we're going to get up to six times as much spatial data overall for the same amount of tow effort, as well as being able to 'stitch together' at fine scales the five cameras' fields of view to create local image mosaics.
"These local image mosaics will allow us to ask questions about the fine scale associations of different species and their importance, which was not previously possible."
SwathCam was built by NIWA's Marine Technology Group, led by Will Quinn. During the design and build the team found some smaller and less-sophisticated cameras recently built overseas, enabling the team to build on some aspects of the simpler systems for the SwathCam.
"We've managed to improve on those overseas examples by adding more capabilities and video cameras on a much bigger frame," says Dr Morrison.
SwathCam has a variety of applications, with more likely to be discovered. For counting fish, it has 24/7 operability.
"Night-deployed SwathCam is particularly effective at counting and measuring fish species that sleep on the seafloor at night, such as snapper and tarakihi - which, during the day, are largely 'invisible' to towed cameras, as they actively move away and avoid being seen," says Dr Morrison.
SwathCam is less invasive than other methods of estimating fish abundance, like trawling, and is more able to distinguish between species compared to other technology such as echosounders, which bounce sound waves off different animals.
To keep the large SwathCam stable during tows, NIWA uses a bridle system with two cables off its wings and a solid weight in the centre.
Dr Richard O'Driscoll, NIWA's chief fisheries scientist, says knowing how many fish are out there is vital information for fisheries managers. "They need to know how fast a fish grows, how old it gets to and what its reproductive rate is," says Dr O'Driscoll.
"We also need to know what the standing stock is - how many sheep are in the paddock, if you like. That data and advice allow managers to set commercial quotas or recreational bag limits and understand what species need to be protected or whether we can catch more.
"When you know how many fish can be taken out of the system, you have a sustainable, productive fishery."
Testing SwathCam produced a couple of heart-in-mouth moments, with fears the huge bar would swing aroundin the water and keep on spinning.
"I think everyone was nervous when we went out and tested it for the first time. Looking at it on the deck, it's a big piece of kit and there was some concern it wasn't going to fly straight," says Dr O'Driscoll.
"But the crew of Kaharoa II and the technical team have worked out a way which means it's very stable when we tow it, and the images were really good."
Mr Quinn says he had many sleepless nights worrying about how SwathCam was going to perform in the water.
"It's a beast. Most things we deploy are much smaller and much less awkward, so this was a real challenge. We've used a bridle system that has two cables off the wings and a big solid weight in the centre, so that seems to keep it pretty much rock solid. It doesn't have a lot in the way of fins to keep it in the current, but it still manages."
The initial deployment trials took place in Wellington Harbour.
"We were really wanting to make sure that it flew right, that it towed correctly and as expected. I had a contingency plan, but it worked out really, really well."
A dynamic GPS tracking system also shows in real-time where SwathCam is behind the vessel, and how 'squareon' its nine-metre frame is relative to the survey vessel's track. This information is used by the survey vessel to make small adjustments such as counteracting water current and/or wind effects, using its bow thruster.
The high-precision GPS tracking data also allows later office-based analyses to accurately overlay SwathCam over other independent spatial data coverages, such as
high-quality multibeam sonar seafloor maps and water current models.
The SwathCam had its inaugural scientific outing in Tīkapa Moana Hauraki Gulf at the end of last year - also the first voyage for Kaharoa II. Scientists collected baseline information on habitats in the Hauraki Gulf Marine Park in a survey funded by Fisheries New Zealand, Seafood New Zealand and the Department of Conservation.
Almost 300 sites were surveyed over three weeks, delivering incredible imagery and a rich set of data.
"There was a lot of sand and mud down there but also an incredible diversity of habitats; the number of fish we saw was really promising," says Dr O'Driscoll.
Dr Morrison says scientists are expecting protected areas in the Hauraki Gulf Marine Park to change over time as the seafloor and the habitats it sustains recover.
"We expect the fish to respond to that habitat recovery positively as well.
"So, by using the SwathCam to capture both habitats and fish at the same time - and over time - we'll get a really good idea of how fish populations are benefiting (higher abundances, faster growth, better survivorship). Benefits which, in turn, flow on to us as well. Such knowledge will also help us in identifying where our best prospects lie for active habitat restoration."
SwathCam's multiple camera technology also enables the creation of 3D imagery using photogrammetry. Such imagery has strong potential for habitat and geological applications, such as quantifying how structurally complex different habitats are, and how different fish species respond to that complexity, or how soft sediment and reef seafloors are being shaped and changed by storm events.
"As a technological science organisation we're always looking to improve and develop our equipment. Here, we built on an internal new innovative NIWA staff idea with the assistance of some overseas parallels, and made it bigger and better," says Dr O'Driscoll.
"It's really exceeded our expectations."
