Object discrimination and avoidance behavior of Polynemus multifilis (Perciformes: Polynemidae) observed in an aquarium

Abstract

Avoidance behavior of Polynemus multifilis (Perciformes: Polynemidae), following contact of the long pectoral filaments (separate rays of the lower part of the pectoral fin) with certain objects (concrete block, same species and carp), was observed in an aquarium. The avoidance rate (avoidance frequency/contact frequency) following contact with a concrete block was significantly higher immediately after the latter was placed in the tank (mean±SD, 68.7±15.4%) than3 days later (0%). The conspecific avoidance rate (10.4±2.7%) was significantly lower than that to carp (83.2±5.3%). Such evidence indicated that P. multifilis could discriminate between and selectively avoid objects by means of the long pectoral filaments.