main idea. A. Some fish have special organs that produce a weak electric field around their body and have receptor organs that allow them to detect disruptions to this field. B. Electrolocation is used primarily by fish who are blind, whereas electric communication is used by fish who are not equipped for acoustical vocalization. C. Research suggests that the effective range of communication by electric signals can reach a little over 1 meter, depending on water resistance. D. Distinctive discharge patterns allow fish with a weak electric system to identify each other by sex or species, or even recognize particular individuals. E. Most fish with a weak electric system have two forms of electroreceptors so that they can detect both very fast and very slow discharge rates. F. Fish can deliberately slow, speed up, or pause their rate of discharge in order to communicate and to avoid confusing their own signals with those of another fish.