Post-spawning defence by male brook charr is linked to perceived paternity

Salmonine fishes are generally thought not to exhibit male parental care, although brief post-spawning mate-guarding by males is known for a number of species, often for populations where eggs are subjected to intense predation (egg cannibalism). Here, detailed in situ data on the spawning behaviour of male brook charr, Salvelinus fontinalis , from a naturally reproducing lake population is used to test whether post-spawning mate guarding (i.e. paternal care) is related to perceived paternity. From video records of spawning events ( n = 20), we documented a novel behaviour whereby the dominant male curtails spawning ahead of the female (by ~ 3 s) and immediately inspects the nest. Afterwards, the dominant male significantly reduces courtship behaviour (quivers) but aggressively defends the female with the same intensity as prior to spawning. The duration of mate guarding (range: 3–48 min), however, declined with increasing numbers of peripheral males that had rushed into the nest at spawning. Neither the number of active females present on the spawning grounds nor male body size influenced the amount of time dominant males spent mate guarding. Extensive revisitation (80% of visits) by males to spawning sites and to females during focal sampling bouts highlights the importance of a male’s ability to predict female readiness to spawn as a significant component of reproductive success. Thus, dominant males appear to guard females at a cost of acquiring other mating opportunities and adjust the time spent guarding depending upon their perceived paternity.