Alaska’s productive marine ecosystems provide livelihoods and support subsistence communities across the state. But Alaska seas are vast, remote, and deep. Ships, money, and time are limited. Collecting the biological and environmental information managers need to maintain productive, climate-resilient fisheries and coastal communities and healthy marine ecosystems is challenging. The Alaska Fisheries Science Center is advancing the use of remote sensing technologies to meet that challenge.
The center uses innovative tools including drones, remotely operated vehicles, eDNA analysis, and stereo camera systems to complement traditional ship surveys. These new tools increase sampling coverage while minimizing the environmental impact and cost of fisheries monitoring and research.
The stereo camera system, developed at the Alaska Fisheries Science Center, offers additional, unique capabilities.
“Stereo camera imagery reconstructs a 3D environment. The image quality is high enough to identify species. Together these allow us to collect a great deal of information from each sample,” said NOAA Fisheries Biologist Kresimir Williams, who developed the stereo camera system with colleague Rick Towler.
High-quality 3D stereo imagery enables scientists to count the number of animals per unit area. It lets them measure the size of animals and their height off the seafloor. It reveals how individual animals associate with other species and with seafloor features. It provides a powerful, versatile tool to collect essential data to inform ecosystem-based fisheries management.
Origin and Evolution of Stereo Camera Sampling
The development of the stereo camera system was driven by the need to make sure that fish sampled in survey trawls represented the population.
“One way to find out was to put a camera in the net,” Williams said.
Towler and Williams determined that 3D imagery would provide the information they needed. It would allow them to see how fish behaved in the trawl—how they were herded and how small fish escaped.
The earliest attempt debuted in 2007. Dubbed the “Pea Pod,” it consisted of a set of green floats with cameras in the middle.
“At that point it was a clunky, low-budget operation. We put commercial cameras in containers, like a ship in the bottle. There were wires everywhere,” Williams said. “But we got good data.”
From there sprung the idea for the CamTrawl, Williams said, “And our big-time leap into stereo camera sampling.”
Sampling Fish Populations—Without Catching Fish
The idea behind the CamTrawl was to use cameras to observe fish going through an open-ended net—without catching them.
“Alaska pollock will swim away from the camera if you just drop it into the water,” Williams explained. “The net provides a closed situation. They have to pass the camera.”
Towler and Williams worked together over 6 years to perfect the CamTrawl system. Williams was the idea guy, and handled funding, optics, deployment, and analysis. Towler was the expert on electronics, embedded systems, and software development.
As they developed the camera system, they partnered with experts at the University of Washington to develop artificial intelligence to automate image processing. This saved an enormous amount of tedious human labor and cost.
CamTrawl has been routinely used in surveys since 2012. Towler and Williams continue to refine the system, introducing new technologies to improve performance and extend capabilities. They built a second system as a backup, which they lend to other NOAA Fisheries science centers and other agencies across the nation. They also helped scientists at the Northwest Fisheries Science Center build a Camtrawl which they use during their West Coast hake surveys. “We can’t make them for everyone, but we made the recipe available so they can make their own,” Williams said.
The stereo camera system has since been adapted to meet an increasing array of research needs beyond the CamTrawl—from surveying untrawlable fish habitat to discovering deep-sea coral habitat on unexplored seamounts.
“Each camera system is more technical and more customized,” Williams said. “We’re able to create these adaptations because we’ve already developed the software. Rick developed a robust system that makes everything else possible.”
Untrawlable Habitat Surveys
The stereo camera system is able to sample steep, rocky areas that nets cannot. These “untrawlable” areas are important habitats for rockfish and other bottom-dwelling species. Unlike pollock in midwater that swim from the camera, most rockfish stay in their territory when the camera is dropped. 3D imagery provides the capability to estimate the number and size of fish in these habitats for more accurate stock assessments.
Deep-Sea Coral Research
The stereo camera played a key role in exploring and mapping deep-sea coral habitat on seamounts last summer. Stereo 3D images allow scientists to identify species, measure sizes, distances between animals, height from bottom, and how close other animals are to particular species of coral or sponge.
“The idea is to not just collect images, but to collect images you can collect data from,” Williams said.
The team has also designed eight small stereo camera units that have been deployed for a variety of research. They include observations of cod spawning grounds, sand lance behavior, and juvenile cod nursery grounds.
Picturing the Future
Williams and Towler are continuing to develop innovative versions of the stereo camera system to expand fisheries research capabilities in Alaska and beyond.
Among these is a camera trap, based on those used to sample rarely encountered terrestrial species. “We want to expand the camera trap concept into the midwater realm,” Williams said. “For that we need a camera that’s not lighting up, but waiting for fish to come to it.”
The team is developing small, ruggedized, next-generation CamTrawl devices for collaborative research with the fishing industry.
Also under development is a drop camera that will be used concurrently with a bottom trawl on groundfish assessment surveys. “When they get to untrawlable grounds, they will now, starting this summer, drop a camera,” Williams said.
A great deal of knowledge will potentially be gained through these innovations. But new information may also be gleaned from existing stereo imagery. “Photo datasets can be revisited many times with a different objective,” Williams said. “I recently went back to an old dataset to see how fish reacted to the approaching camera.”
In all of these endeavors, 3D imagery will provide valuable information. It also offers humans an experience that no other sampling technique can match.
“The camera lets us interact in a more personal way with this place where we don’t belong,” Williams said. ”It’s a way to immerse ourselves in it. It’s powerful stuff.”