Fright reaction in Gymnocharacinus bergi (Pisces, Characidae), a relic fish from Patagonia

MARIANA LOZADA; SILVIA ORTUBAY; V´ıCTOR CUSSAC

ENVIRONMENTAL BIOLOGY OF FISHES

Año: 2000 vol. 58 p. 227 - 232

0378-1909

Fright reaction, mediated by pheromones, is an antipredatory mechanism in the scale-less ‘mojarra’Gymnocharacinus bergi (Pisces, Characidae). The aim of this study was to characterise and quantify the frightreaction of this species and to analyse the alarm response to different doses of alarm substance. The alarm responseconsisted in a general decrease in the swimming speed and a tendency to remain at the bottom of the test aquarium.A threshold effect was induced by a very low dose of alarm substance, and the intensity of the fright reaction waspositively correlated to the dose concentration. The main characteristics of the alarm response appear to be consistentwith G. bergi’s environmental conditions such as: a higher predation risk in the upper stratum, the abundantpond-weeds of the stream and the great flow and fast speed of the clear waters.