Robot to track sharks
This summer, an underwater robot will start tracking white sharks to learn more about their habits. Biologist Chris Lowe from California State University Long Beach and engineer Chris Clark from Harvey Mudd College in Claremont, California, have been developing a shark-tracking robot for the past three years.
Marine scientists have used autonomous underwater vehicle (AUVs) to collect oceanographic data for decades, but the technology to simultaneously track a moving animal has only developed within the past three years. Other robots now follow marine mammals, but this is the first designed specifically to track sharks.
The team uses hooks, lines and nets to catch a shark in the wild, then attaches a transmitter tag to the shark’s dorsal fin and releases it back into the wild. Then the AUV follows along at up to four miles per hour, always remaining 300 to 500 meters behind the shark so as not to alarm the fish. “We have programmed the robot to not disturb the shark’s behavior,” says Lowe.
Two hydrophone receivers, situated on the front and rear of the AUV, pick up acoustic signals from the shark’s tag every second, and sends the signals back to a land-based computer that converts the signals into a map of the track. Physical and chemical sensors on the AUV send environmental data, such as dissolved oxygen, temperature, and salinity, to the computers, while an image sonar and a high definition camera collect snapshots of the path. “We know where [shark] hotspots are, but we don’t know what makes these spots special,” Lowe said.
Last summer the team tracked a leopard shark off the coast of Los Angeles. Since then, Clark and Lowe have refined their prototype to be more hydrodynamic and the software has been tweaked to allow two robots to work simultaneously. These adjustments will help conserve battery power — one of the main limitations of the project’ currently, their longest track is six hours, but they hope to reach at least 20 hours in the future. This summer, the team plans to use their robot to track a juvenile white shark off Southern California.
Meanwhile, at the Woods Hole Oceanographic Institute in Massachusetts, engineers are currently designing a similar shark-tracking robot for use on the East Coast, and hope to have it ready for the field this summer..
On the East coast, shark biologist Greg Skomal of the Massachusetts Division of Marine Fisheries has tracked basking sharks and white sharks using satellite telemetry, and is working with WHOI on their robot. He is optimistic about both the East and West Coast projects. “This is great, new, innovative technology that will allow us to do unmanned tracks,” Skomal said. “I think it’s healthy to pursue two different lines of development, see which works, and then ultimately take the best results from both.”