Ocean going drones in the Bering Sea are helping researchers with the Alaska Fisheries Science Center gain new insight into the foraging habits of female northern fur seals, whose populations have been declining since the 1970s.
“This is really a test project for us,” says Carey Kuhn, an ecologist with the Alaska Fisheries Science Center, who has been blogging her observations online since the start of the 2016 Saildrone mission.
Kuhn and others with the Center have been reviewing early results from satellite tags on 30 adult female fur seals tracked by unmanned sailboats made by Saildrone technology. The autonomous surface vehicles are equipped with meteorological and oceanographic sensors and have the capacity to increase observational infrastructure in remote and hostile polar regions where ship time and human labor would be costly and potentially hazardous.
The ongoing development of Saildrones, NOAA researchers note, is a collaborative effort of researchers at the Pacific Marine Environmental Laboratory, the Joint Institute of Atmosphere and Ocean at the University of Washington, the University of Alaska Fairbanks, and Saildrone Inc. The wind-and-solar powered Saildrone incorporates the principles of sailing and scientific research with a nearly 20 foot high carbon fiber wing that speeds through water with a suite of high resolution sensors. The Saildrones can carry over 200 pounds of instrumentation, travel at speeds up to 16 miles an hour, and are quickly maneuverable.
The saildrone mission is unique because it allows for deep collaboration covering an expansive area over an entire summer, Center officials said. The female fur seals were tagged to learn more about their foraging habits and on walleye pollock, the seals’ main food source.
Kuhn said researchers are getting a better idea of the prey available to fur seals in summer months, which may help them unravel why this population continues to decline. Reduced prey availability is just one hypothesis for population decline, she said. Before any decisions are made on changes in fishery management, researchers need to understand what’s going on with the ecology of the fur seals, and have strong scientific backing for those observations, she said.
After reviewing early results from satellite tags, researchers learned that one seal travelled 165 miles for food, spending six days away from her pup, and that another female regularly travels just 50 miles, leaving her pup for three to four days.
Kuhn said researchers suspect there could be negative consequences for pups whose mothers are gone for extended periods, because the pups can’t nurse.
She has been closely monitoring limited real time data coming from tags glued onto the fur seals. Through Aug. 22, the two Saildrones involved in the project had already surveyed more than 1,700 miles within the fur seal foraging area. Devices attached to the unmanned boats are measuring and locating walleye pollock, the main food source of the fur seals.
Kuhn said she is really looking forward to going back to St. Paul Island to weigh the seal pups, measure their growth and recover the tracking instruments.
The Saildrones will also make a quick trip to the east to listen for critically endangered North Pacific Right whales, as there are just an estimated 30 left. Then both boats will head back to Dutch Harbor for the mission’s end.
It will take an estimated couple of months for Kuhn and her colleague, Fisheries biologist Alex DeRobertis to process all the information from several people.
Using saildrones we can focus surveys on pollock in the areas they use, and how their behavior changes in areas where there is abundance of no fish, sad Kuhn.
“We are looking at how long they spend at sea feeding,” she said. “How often do they have to dive?
“We are trying to link how much fish is there, how these animals behave in trip durations, and that it means for their pup’s health,” she said.
