The mating ritual and patterns of monopolar electrical pulses in Hong Kong catfish Clarias fuscus (Clariidae, Siluriformes)

Laboratory experiments were performed to compare the electrical activity and behavior in Clarias fuscus during spawning. Each of the multiple matings of the male and female was preceded by an amplexus - a mutual pose in which the male tightly covers the female’s head and remains in close contact with it until the end of mating. The spawning behavior of C. fuscus was accompanied by monopolar electrical pulses (MP) of two types: single MPs, similar to those observed in other behavioral situations (aggression, hunting) and specific MPs, observed only during spawning bursts of serial MPs (burst MPs), at intervals which are comparable with their duration. Each recorded burst MPs (71) corresponded to one mating, and each recorded single MP (63) corresponded to an attack of one fish on another. In different behavioral situations (matings and attacks), MPs differ significantly in amplitude and duration; and for MPs in bursts, in their degree of asymmetry. It can be assumed that the involvement of MPs in the spawning behavior of C. fuscus is similar to that studied earlier in Clarias macrocephalus, and is a common feature for Clariidae.