How Fish Use Electricity to Hunt and Communicate
All fishes produce a slight electric field as a by-product of the nervous impulses intrinsic to life. However, some species have harnessed and concentrated this ability to enable them to communicate among themselves, to locate prey and, in some cases, to deliver a powerful shock to subdue other animals.
Which fishes use electricity and what do they use it for?
Normal muscle tissue produces tiny electrical impulses with each movement -- this is why hospital monitors can detect the patterns of a human heartbeat. A number of fish species, such as the elephant-nosed fishes of Africa, the ghost knifefish of South America, and the knifefish of Asia and Africa, all live in dark or cluttered environments where vision is difficult or impossible. Instead, each has specialized muscle cells arranged along its flanks that produce electrical fields that spread a few inches around themselves, almost like an electrical radar. If an object is detected within this field, the fish is able to distinguish whether it is a rock, a clump of plants or an animal by its electrical conductivity - each conducts electricity differently because of its physical properties. This produces an electrical map of the immediate environment in the fish's brain, helping it to navigate with extreme precision and to find prey in its habitat
So is electricity used for hunting?
Very much so. Some fish, such as Xenomystus and Notopterus, which lack the ability to produce an electrical field themselves, are able to find hidden prey by detecting the minute electrical signature that all live animals produce, almost as if they were using X-ray vision. They can use this ability to find prey animals hidden deep within the substrate, where they are beyond the detection of most other fishes.
Do they use electricity for anything other than finding their way around?
As well as for navigation, elephant-nosed fish use their electrical abilities to communicate with one another. In the simplest example, if two of these fish are hunting in close proximity, one will switch its electrical output to a different frequency so that it does not jam the signal of the other. But the communication becomes much more sophisticated. Males of some species produce specific courtship "songs" during the mating season using electrical impulses to attract females, which can be detected up to 3 feet (1 meter) away.
Fights and aggression are also mediated through electrical communication, Aggressive individuals increase their rate of electrical discharges before they attack. If the intended victim wishes to signal its submission, it correspondingly decreases its rate of electrical emissions.
Can electric fish zap their prey?
A small number of fish, including the catfish, have taken the ability to generate electricity even further. They can generate considerable voltages, which they use to stun their prey before eating it and also to discourage any predators that might consider them as a meal.