Behavioral response of Nile tilapia to an allopatric predator

We investigated interaction of the Nile tilapia, Oreochromis niloticus, paired with either a predator, spotted sorubim, Pseudoplatystoma corruscans, or a nonpredator, threespot leporinus, Leporinus friderici. Fish behaviors were quantified 5 min before pairing and 15 min during pairing (a heterospecific fish introduced into the Nile tilapia aquarium). Distance from the heterospecific fish, frequency, and time spent in dorsal-fin display, and frequency of agonistic interactions were registered. Agonistic interaction occurred mainly between Nile tilapia and threespot leporinus. Pairing increased frequency and time spent in dorsal-fin display, mainly when tilapia was paired with the threespot leporinus. Tilapia kept further away from spotted sorubim than from threespot leporinus. We concluded that Nile tilapia discriminates a predator from a harmless nonpredator allopatric heterospecific, suggesting a genetically-based ability. The dorsal-fin display is interpreted as both anti-predatory (displayed to the predator spotted sorubim) and intimidator behavior (displayed to the threespot leporinus).