Underwater Robots Tail Sharks

A group of scientists and engineers in California is using underwater drones to track single sharks' movements. ->

Humans aren't good at following sharks. We're noisy in the water, need to breathe air and the animals generally get disturbed when we're around. So a group of California universities put together a project to use autonomous underwater vehicles, or AUVs, to do the job.

To track the sharks, the scientists first caught them and attached a tag to their dorsal fins. The tag sent out an acoustic signal, like a "ping" from sonar. The sharks were leopard sharks, Triakis semifasciata, which are typically less than five feet long, and generally aren't dangerous to humans.

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The scientists then dropped the robot in the water. The robot listened for the ping, and the on-board computer did a quick calculation as to where the shark is. It then followed the shark, needing no direction form its handlers. The research was published in the latest issue of the Journal of Field Robotics.

Christopher Clark, a professor of engineering at Harvey Mudd College in Claremont, Calif., and one of the co-authors of the paper, noted that the robot is designed to track individual animals. That can provide valuable information about their habits. "We're looking at fine scale movement," he told Discovery News.

The idea of using AUVs to follow sharks isn't unique - there is a similar project called the Oceanographic Telemetry Identification Sensor, or OTIS, out of the University of Delaware. Clark has collaborated with the teams using that technology, and noted that the difference is OTIS tracks large-scale conditions and movement - it's geared to tracking what regions sharks like to be in, rather than following an individual closely.

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One technique the California team tested was tracking the shark with two robots. One of the features of the technology Clark's team built is that the robots can communicate with each other, using a set of acoustic signals similar to the ones they receive from the shark tags. By programming one robot to send its location to another, the first robot can say "I am at this location, this distance from a shark. Please stay a similar distance away," using one of the AUVs as a reference point. The robots could then circle the shark, getting a much more accurate picture of where it was.

The sharks were tracked off the coast of California. Clark said the team hopes to do another set of experiments with bigger shark species, perhaps even juvenile great whites.

Image: Courtesy Christopher Clark