ABSTRACT

Most fish species depend either on vision, olfaction, taste or tactile senses to find and ingest food. Initially, the sensory input that provides the most direct information to the central nervous system (CNS) leading to the potential target(s) has priority. Different species of fishes are specialized for different ecological niches. Specialization to a specific niche determines which sense organ is best for the detection, search, and location of the food (Valentincic, 2004). In clear water, vision provides predatory fishes with the most precise target location. Omnivorous fishes, in addition to vision, use olfaction and taste to detect and localize food. Vision enables a direct approach to the food, whereas olfaction merely signals its presence. Except at a very close range outside water currents, chemical senses do not provide directional bearings for the food site. In omnivorous fishes, chemical stimuli release food searching behavior resembling klinokinesis (Fraenkel and Gunn, 1940). Rapid swimming and turning behavior of the fish during feeding excitation greatly increases the chances of a direct encounter with the food. In fishes with barbels, such as catfish (Fig. 3.1), taste enables tropotactic location of food, which occurs generally over millimeter distances upstream and to the sides of the food item and at somewhat larger distances downstream.