The mate-guarding behaviour of male kokanee Oncorhynchus nerka

The patterns of mate-guarding in kokanee (non-anadromous Oncorhynchus nerka) are analysed and discussed in relation to existing theory of precopulatory mate-guarding. Male salmon typically guard females prior to spawning events and aggressively exclude other males from their vicinity. Mate-guarding is thought to increase the likelihood of releasing gametes before other males (during a spawning event) and fertilising the greatest proportion of the clutch. The optimal duration of mate-guarding can be considered in a game context because the mate-guarding behaviour of other males influences the probability of finding an unguarded female if a male leaves a female in search of other opportunities. At the Meadow Creek spawning channel, males guarded females, searched for unguarded females, or joined groups of non-breeding males and females. In accordance with mate-guarding theory, males continued to guard the same females after presumed spawning events (but during her egg deposition period) more often than expected on the basis of random pairing. This prevented some males from ever pairing with females. Gaining familiarity with habitat features may confer a competitive advantage to mate-guarding males and may favour prolonged mate-guarding. Because of the importance of finding nesting females quickly, before other males, unpaired males may wait for pairing opportunities rather than occupy distant satellite positions to breeding pairs.