If it Looks Like a Fish
If is looks like a fish, swims like a fish and sounds like a fish, it must be a fish. Right? It works for ducks. It used to work for fish, but no more. Dr. Xiaobo Tan of Michigan State University and his students are developing a robot to use in Lake Michigan and the other Great Lakes that looks, swims and sounds pretty much like a live fish.
They aren’t just doing it for fun, or in a competition to see which university engineering department can develop the most animal-like or fish-like robo-creature. Dr. Tan believes a robo-fish or even a school of robotic fish swimming the Great Lakes can provide scientific answers to questions hard to come by using more traditional technology.
The problem is, for the most part, traditional technology - specifically the cutting edge tools used to track the movement of fish is basically static. The best available right now is the Great Lakes Acoustic Telemetry Observation Systems (GLATOS) in which a series of underwater receivers are deployed in what the researchers hope are strategic locations and the receivers capture signals from fish outfitted with internal transmitters when they swim by.
The transmitter-equipped fish move, the receivers are stationary. The fish have to be quite near a receiver for it to pick up its signal so naturally, in lakes the size of the Great Lakes there are far more areas where there is no receiver than areas where the equipment can pick up the presence of a marked fish.
What if the receiver could swim and just follow the transmitter equipped fish where ever it goes? The researchers would have some real meat to digest. In the case of a spawning fish, knowing where it lives most of the time and then where it goes to spawn unlocks vital information. Coded wire tag studies on king salmon show these fish wander all over the lake (or lakes, since Lake Huron fish show up in Lake Michigan and vice-versa.) Why is this? If a northern Lake Michigan fish spends a lot of its time in southern Lake Michigan what conditions exist to lure the fish so far from where it was expected to go.
Is it the availability of food? Is it lake currents, water temperatures or some other unidentified factors or combination or factors? Being able to “real time” track these fish with a robo-fish unit can help provide the answers - someday. These robo-fish, called GRACE by Dr. Tan and his colleagues aren’t quite ready for prime time. The name, GRACE stands for “Gliding Robot ACE.”
Most man-made machines designed to travel underwater are like submarines. They have a propellor and rudder. Some work like underwater personal water craft and have thrusters or some sort of jet propulsion. Like a fish, GRACE moves through the liquid environment with a powerful tail fin to propel it forward and the movement is further enhanced with a glider system with employing side fins (as do fish) and by changing its buoyancy by pumping up or reducing the amount of gas inside - something like a real fish uses its’ swim bladder.
GRACE moves through the water both by flapping its’ tail to propel itself forward and by ascending and descending through the water column and allowing the glider affect of its’side (pectoral) fins to move it along. This is an exceptionally efficient configuration, giving GRACE an enviable multi-week endurance on a single battery charge.
The original GRACE was basically just a test of the robot to see if, or how well, it moved through the water. GRACE, version 2.0, was out for testing last summer. This one had equipment loaded in it to scan and monitor its surroundings and to test the ability for the transponder to pick up readings from fish implanted with GLATOS transmitters.
Dr. Tan doesn’t envision being able to actually gather much useful data from a fisheries point of view until the third incarnation of GRACE is deployed sometime in the next year or so. Actually, once GRACE three is launched (stocked) in the lake, the next step is to go into production of additional G-3 models. Once there’s a school of these robo-fish dogging the salmon, lampreys, walleyes or other species of concern in the Great Lakes, major insights to fish movements and what they mean will soon follow.