Flexibility in Reproductive Styles of Male St. Peter's Tilapia, Sarotherodon galilaeus (Cichlidae)

Abstract

This study examins the flexibility of the reproductive styles in St. Peter's tilapia, Sarotherodon galilaeus (Cichlidae). Three years of monitoring and filming 111 reproduction cycles involving 15 individually marked males, revealed their behavioural repertoire to contain 12 dominant groups of tactics (marked A to L), revolving around three parameters: territoriality (T) or non-territoriality (NT) during spawning; brooding-participating (Br) or non participating (NBr) in brooding eggs; and pairing (P) or not forming (NP) pair bond with the selected female. The males demonstrate an ability to select alternative reproductive styles (ARS) that presented various combinations of the three major parameters. The most dominant group comprised T (territorial) males, which tended not to brood eggs and to desert the female after mating. However, over various reproductive cycles the same males also altered their behaviour from one tactic to another. Territoriality was the most conservative tactic, while brooding or not brooding was the most frequently changed tactic. Some types of males remained with their selected mate for one spawning only, whereas others stayed for up to five cycles, showing a high tendency toward monogamy. In some instances the presence of additional females influenced the decision-making of the male, decreasing his fidelity to his mate. The rich variety of reproductive tactics in S. galilaeus males and their ability to change from one tactic to another, characterizes the high flexibility and adaptability of this species. These qualities could be used to describe ecobehavioural morphs, similar to descriptions of ecomorphological or ecophysiological phenotypes.