Ocean gliders listen for whales off Oregon in test of new ways to count them
by NOAA Fisheries 8 Dec 2024 23:25 GMT
Three small autonomous underwater gliders called Seagliders crisscrossed the ocean off the Oregon Coast in recent months. They were listening to underwater sound in trial research to find new ways of tracking and counting whales and other marine mammals.
The research trial is funded through Inflation Reduction Act essential data acquisition efforts. It is a collaboration between Oregon State University and NOAA Fisheries Southwest and Pacific Islands Fisheries science centers. The underwater "gliders" soar through the ocean over long distances. They promise to supplement existing surveys conducted on research ships where scientists count marine mammals through binoculars.
"There is a very rich soundscape underwater, extending into frequencies we cannot hear," said Shannon Rankin, research scientist at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, California. "We can study a lot of things by recording them passively, and return to these recordings as we discover new sounds in the ocean."
The research funding promotes climate-ready fisheries by helping develop information and tools to adjust fisheries management in response to climate-driven shifts.
NOAA Fisheries surveys marine mammals to develop stock assessments that gauge their population size and trends. The data help inform management decisions about fisheries and other ocean uses that may affect marine mammals. For example, managers may use marine mammal and environmental data to help fishing fleets avoid waters where they may inadvertently entangle whales. Managers can also use this information to predict how those areas may shift with climate change.
Part of the current effort is to understand how data from autonomous vehicles can augment the data collected by research ships to aid in these management efforts. "Underwater gliders simultaneously collect marine mammal occurrence information by listening for their sounds and oceanographic data with onboard sensors. They provide a rich dataset that is relatively inexpensive to collect and can help us describe and monitor marine mammal habitat, as well as species range and relative abundance as the climate shifts," said Erin Oleson, Protected Species Division Director at NOAA Fisheries Pacific Islands Fisheries Science Center in Honolulu, Hawai?i, and co-lead on the project.
Gliders Join Ship Survey
The three Oregon State gliders were listening for whales off Oregon using passive acoustic monitoring, which records underwater sounds. Marine mammal observers from the Southwest Fisheries Science Center were also surveying waters off Oregon at the same time on a survey ship. Running the surveys simultaneously allows scientists to examine the two streams of data to determine how they could best collect the details they need on marine mammal populations.
"Passive acoustic monitoring may better detect some whales, for instance. Beaked whales make up a quarter of all cetacean species but dive deep after their squid prey for as long as 2 hours," said David Mellinger, a professor at Oregon State University who began using gliders about 15 years ago to listen for whales. The beaked whales do not display a prominent "spout" when they exhale at the surface, so are often hard to see. This means they may be undercounted in traditional visual surveys.
However, beaked whales use sound to hunt, which the gliders can hear and record. That gives the gliders some advantages in helping understand beaked whale distribution and behavior and their role in the marine ecosystem.
More Trials Planned
The gliders travel more slowly than ships but they can cover large areas over long time periods, relying only on battery power and buoyancy to move. "The research is part of a larger strategic initiative. We're exploring the use of passive acoustic monitoring and autonomous vehicles, such as gliders, to collect essential data on cetaceans that we have not been able to systematically collect in the past," said Selene Fregosi, research scientist at Ocean Associates, Inc, contracted to the Pacific Islands Fisheries Science Center.
"We are looking at the question of, 'How do we put this into practice?'" she said. "We want to go from research to an operational plan. How can we leverage the technology to get more data about cetacean stocks in the most efficient way."
Rankin, Oleson, Mellinger, Fregosi, and a large team of scientists across the two Science Centers are collaborating on the Oregon whale survey. It's the first stage of the project to explore autonomous technologies. The Oregon State University glider lab and Oregon Coast Aquarium assisted in preparing and deploying the gliders.
The NOAA Fisheries teams are planning a second ocean trial using gliders and a research ship near Hawai?i in February 2026. The Hawai?i project will again use the OSU Seaglider, as well as new Pacific Islands Science Center Seagliders and the Southwest Fisheries Science Center Slocum gliders to listen for whales and dolphins around the main Hawaiian Islands. A research ship will carry out surveys in the same study area. The larger project also includes two "Glider Rodeos" on the West Coast and in Hawai'i over the next 2 years. The rodeos will assess four different types of gliders and three different acoustic monitoring systems. The trials will help scientists understand the advantages of different gliders, which may inform future decisions on what systems NOAA Fisheries should use.
Species Identification in Near Real-Time
Fregosi doubts that autonomous gliders could ever completely replace research ships. However, they could supplement data between ship surveys and survey areas ships may not often go.
Scientists also wanted to know if the gliders could report the whales they are detecting in real time. While gliders typically "check in" via satellite, they cannot transmit much data. So scientists usually have to wait to retrieve gliders before examining their data.
However, Mellinger programmed the gliders to identify the signature sound of sperm whales and promptly report the detections. "We are trying to get smarter about the way we collect this data, so we're putting the resources and capabilities in the right place to make the most of what they can do," Mellinger said. The timely data could prove useful in cautioning fishing fleets to avoid areas where they might entangle whales.
Mellinger reports the gliders have been detecting a substantial presence of sperm whales off Oregon. One of the next steps is to determine how well gliders detect other species of whales and dolphins. Then we would develop statistical methods to use the glider data for NOAA's assessment of marine mammal populations. Work on this front is also funded by the Inflation Reduction Act.
Eventually we hope to continue routine passive acoustic glider surveys to monitor marine mammals in offshore environments. "In many cases the gliders hear animals more often than a ship sees animals at the surface," Fregosi notes. "That gives us access to a treasure trove of new information that we can use to ask and answer many more research questions."