ABSTRACT
Although all fishes have a mechanosensory lateral line system – a system of water flow detectors (neuromasts) in canals or free on the skin’s surface – particular behavioral functions are documented for only a few species. Work on lateral line use for feeding has focused on either cavefishes or night-active species (Montgomery, 1989). While surface-feeding fishes with well-developed eyes do use the lateral line to locate prey (Müller and Schwartz, 1982), it is generally assumed that diurnal/crepuscular fishes are visual predators. We show that a hydromechanical stimulus detected by the cephalic lateral line system in two sunfishes (Centrarchidae) can be the sole determinant of a strike trajectory. The response occurs without reinforcement and appears to be an unconditioned response. Green sunfish (Lepomis cyanellus Rafinesque) and largemouth bass (Micropterus salmoides Lacépède) are North American sunfishes that inhabit ponds, lakes and slow streams. Both species have diverse diets, including invertebrates and fishes (Carlander, 1977). These species and their congeners are active during the day; at night in field and laboratory they lie near or on the bottom and are lethargic (Neill and Magnuson, 1974; Helfman, 1981). Both species have cones and rods in the retina; the green sunfish visual pigments are characteristic of crepuscular mid-water fishes (Dearry and Barlow, 1987;
