The New Guy Looks Fishy

As a resident of Florida, I can tell you firsthand how incredibly annoying mosquitoes can be. And in other parts of the world, where malaria is endemic, the nasty little winged bloodsuckers are far more than just a nuisance. It is no wonder then that in many parts of the world, where the eastern mosquitofish is not native, it has been introduced into local ecosystems. As their name implies, these little fish love to gobble up mosquito larvae, which keeps populations of the pesky disease-spreaders under control without insecticide.

But before you run off to release these tiny aquatic heroes into every body of water within five miles of your home, and name your firstborn child Mosquitofish, a word of caution. They also have a nasty habit of chewing the tails off of freshwater fish and tadpoles, then leaving them to die. How very rude! Because these fish have been found to be so unneighborly and generally destructive to natural wildlife populations, many people are having second thoughts about having introduced them, and are looking for ways to reduce their numbers.

Unfortunately, there is no easy way to put the genie back in the bottle; no means of reducing eastern mosquitofish numbers without also harming other wildlife is presently known. Perhaps this situation is about to change thanks to some new research coming out of the University of Western Australia and New York University. They have designed a robotic predator that scares mosquitofish to the point that they have a reduction in fertility, which is expected to reduce their numbers as a result.

The creepy looking robot fish (who would not be scared of this thing?) was designed to mimic the largemouth bass, which is a natural predator of the mosquitofish. The current prototype robot is fairly simplistic, and not free-swimming. It is attached to a clear acrylic rod, and moved about an aquarium via magnetism. The movements, which are designed to mimic a real largemouth bass, are coordinated by an Arduino microcontroller and a set of three stepper motors.

A computer vision system was developed in MATLAB that allows for discrimination between mosquitofish and other aquatic creatures. Using this visual information, the robot was made to “attack” the mosquitofish closest to a tadpole at a frequency of one attack per minute. After a series of trials, eastern mosquitofish were found to show weight loss and changes in body shape, in addition to the aforementioned reduction in fertility. These effects were noted to last for several weeks, even after the attacks halted.

As it currently stands, the robot is too simplistic to operate in the wild. It would require a substantial additional effort to create free-swimming robots that could operate in natural environments for any length of time. The computer vision system would also need to be reworked to operate outside the confines of an aquarium. These are significant hurdles that will not be accomplished overnight, however, this prototype presents an interesting path for future research in controlling invasive species.