If you have been following our recent field notes posts, you are aware of efforts at FISHBIO to track salmon and bass throught California. These projects require us to place stationary hydrophones (acoustic listening devices) at several key points along rivers to ‘listen’ for tagged fishes. This way we will know if a tagged fish has left an upper stream reach and entered the Delta. It is relatively easy to set up an array of hydrophones in a river to ensure that all passing fish are detected. After all, you can see across most Central Valley rivers but what do you do if you are trying to track fish across the wide expanse of the oceans surrounding Alaska?
In the past, researchers have tried several techniques including lowering mobile hydrophones from ships; however, this requires a ship to be in the area, and it can be quite expensive to run a scientific vessel (i.e. gas, food for a hungry crew, salaries, etc.). Researchers at University of Alaska Fairbanks took up the challenge and have devised a creative solution. They propose to use remotely-operated, autonomous underwater vehicles (better known as ‘gliders’) to track tagged fish in the ocean. These gliders are about 5 feet long and look a bit like a cross between a yellow submarine and a torpedo. They move in a zig-zag motion between the surface and a set depth, over 3,000ft, and are generally used by marine scientist to gather data on oceanic conditions (i.e. temperature, salinity, pressure, and nitrate concentration). The gliders can cover thousands of miles and can be programmed to transmit resulting data to scientists at the surface the via satellite communication. To test this method the researchers planted tags underwater along a line of buoys and deployed the gliders with acoustic listening devices. In the future, gliders may even be programmed to follow tagged fish.
Video source: University of Alaska