Visual cues during the alarm reaction of Gymnocharacinus bergi (Pisces, Characidae)

VICTORIA CORDI; SILVIA ORTUBAY; MARIANA LOZADA

Journal of Appied Ichtiology

Blackwell Verlag

Lugar: Berlin; Año: 2005 vol. 21 p. 487 - 491

0165-1587

Gymnocharacinus bergi (Pisces, Characidae), an endemic fish inthe headwaters of the Valcheta stream in northern Patagonia,displays a fright reaction. As this species inhabits a rapidstream, we hypothesized that the alarm reaction might besocially transmitted through visual information, because thedetection of alarm pheromone would be restricted to those fishlocated downstream from the releaser. Alarm substanceselicited a decrease in the swimming activity and a tendencyto remain at the bottom of the aquarium. Individuals thatobserved the fright reaction, but were not exposed to thepheromone, spent significantly more time at the bottom of theaquarium imitating the alarm response, and tended toapproach the others. Gregarious behaviour was observed;however, interactions (number of approaches) were strongerbetween those fish held prior to testing in the same aquarium;smaller fish in particular tended to get closer to bigger ones.Greater group cohesion was found between individuals thatwere exposed to the alarm pheromone.