Prey Location
Passive Electrolocation
Electric fish can use their ability to generate and receive electrical pulses as a method of predation. All marine animals emit small electric discharges, which are conducted well in the surrounding water. Electric fish detect these discharges from potential prey animals and use them to locate the prey. Fish can determine exactly where the prey is, how it is moving, and even how to attack most effectively (von der Emde 1999). Electrolocational predation has a number of advantages. It allows electric fish to survive on prey populations that they normally would not be able to hunt, such as prey that would be too well hidden without electrolocation. It also compliments other sensory modalities and provides the predator with a more complete picture of the prey, which can aid in capture.
Though sharks and rays are the most well-known electrolocational predators, a number of fish employ this technique. Below are some examples of electrolocational predators.
Paddlefish
Paddlefish. Image used with permission of Nature's Images.
Paddlefish (Polyodon spathula) are a freshwater species that feed on zooplankton. Adult paddlefish filter feed, but juveniles lack functional gill rakers that allow filter feeding, so they detect and capture zooplankton individually. Paddlefiah live in muddy water environments and have poor visual systems, so they use detect the zooplankton electrically (Wilkens et al.1997).
Dogfish
Hunting with electrolocation is especially adaptive to the smooth dogfish Mustelus canis. The dogfish feeds on small fish that move very quickly and sometimes hide in the sand to avoid predators. Using electrolocation, the dogfish can pinpoint its prey’s location very accurately, even through a small barrier of sand. Accuracy is essential to the dogfishs’ hunting strikes, as its prey moves away too quickly if the first strike is a miss (Kalmijn 1982).
Blue Sharks
Electrolocation of prey has been well documented in a number of shark, skate, and ray species. Studies with blue sharks (Prionace glauca) have shown that sharks preferentially attack electrically simulated prey over prey simulated by odor (Kalmijn 1982) .
NOTE: In passive electrolocation, the electric fish simple detects electric fields of other animals. In active electrolocation, the fish is both creating and detecting the electric field, and located objects by analyzing disruptions in the field.
This website was created as a part of a class project in the Animal Physiology Class at Davidson College.
