Using an Autonomous Underwater Vehicle to Survey West Coast Habitat and Fish
Some ocean creatures are a challenge to study. They live in places that are difficult to get to or have complex life cycles. Sometimes scientists need unique tools to study unique creatures.
What is an Autonomous Underwater Vehicle?
Autonomous underwater vehicles, or AUVs, are uncrewed, untethered vehicles scientists use to conduct underwater research. AUVs are independent and unlike remotely operated vehicles (ROVs), which are tethered to a service vessel by an umbilical.
AUVs are either pre-programmed to conduct specific tasks during each dive or receive commands from an operator-controlled computer directing them where, when, and what information to collect AUVs carry a variety of equipment for sampling and surveying, such as cameras, sonar, and depth sensors. They can range in size from a few hundred to several thousand pounds.
Anatomy of an AUV
For years, scientists collected data by dragging trawl nets, but these methods are not effective where the sea floor is rocky and rugged. In 2005, NOAA Fisheries and the Woods Hole Oceanographic Institute (WHOI) collaborated to reconfigure the existing SeaBED AUV useful for surveying fish and their habitat in rugged areas.
The SeaBED AUV is unique because it "flies" a few meters above the sea floor instead of remaining in the water column like many other AUVs. The SeaBED AUV takes photographs every few seconds. These images provide a photographic record of fish and their habitat. This capability allows scientists to gather more information in rocky areas than ever before.
The AUV consists of two hulls connected by aluminum spars. The lower hull is negatively buoyant (it sinks). The upper hull is positively buoyant (it floats). This creates a stable platform, able to tolerate the ocean’s pitch and roll. Three carbon fiber propellers, initially designed for use in model airplanes, provide the thrust needed to propel the AUV down to the sea floor.
NOAA Fisheries’ West Coast Deep-Sea Coral and Sponge Research Program and its AUV, Popoki
Since 2010, the Northwest Fisheries Science Center’s (Center) AUV Team has joined scientists from NOAA, other federal agencies, and academia in a collaborative research effort to understand better the location, distribution, status, and health of deep-sea coral and sponge ecosystems and to inform conservation and management actions.
We named the SeaBED AUV used by the Center's team Popoki. Popoki means cat in Hawaiian. The name refers to the cat-like stealth of the AUV as it moves along the bottom.
Popoki can dive 2,000 meters deep. It will work underwater for up to 7 hours while sending information back to scientists onboard their research vessel. Some pieces of information are relayed to the ship via an acoustic micromodem. Most of the information from sensors is saved on the AUV’s internal computers. Then the information is downloaded after the AUV is back on board a vessel.
Popoki can cover a 5 to 10-kilometer transect in a single dive. Then we can analyze the AUV’s images to provide quantitative information on the abundance of deep-sea corals and sponges.
The thousands of pictures taken by Popoki can also be blended into larger photomosaics. These mosaics provide a more complete perspective of the ocean floor than is currently available. The information gathered by Popoki allows researchers to explore the relationship between fish, invertebrates, and their habitats.