here are some photos from two different occasions: electrofishing near braz, vorarlberg (for a fish population estimate), and river sediment sampling near pfaffenhofen, tirol (for zoobenthos estimates).
in both cases, it was my first time to the method being applied in the field. both proved to be very interesting, but it’s also exhausting to be standing in a river all day. :-)
electrofishing uses an effect called galvanotaxis: direct current causes muscle-contractions in the fish, making it involuntarily swim to the power source. there, they’re stunned and caught, later on measured, weighed, and released back into the water without being harmed.