Kin discrimination in salmonids

Summary The data presented here suggest that significant selection pressures towards kin discrimination behaviour patterns result from kin-biased territorial defence behaviour patterns. Salmonids employ a phenotype matching recognition mechanism allowing individuals to discriminate unfamiliar kin. Kin discrimination abilities allow individuals to reduce the levels of aggression associated with territorial defence towards related conspecifics and to defend smaller territories near kin versus non-kin. This kin-biased territorial defence behaviour is observed in at least one species under a wide range of territorial quality conditions. Within kin groups, subordinate individuals obtain a greater number of foraging attempts, resulting in kin-biased foraging within the social group. As a result of this kin-bias, individuals within kin groups show significantly higher mean weight increases (increased direct fitness benefits) and reduced variance in these increases (increased indirect benefits). Since all individuals within the kin groups obtained higher, less variable weight increases, we can argue that individuals are increasing their inclusive fitness as a result of these kin-biased behaviour patterns.Based on these results, and on what is known about the life history of a variety of salmonid and non-salmonid species, we can formulate a number of testable predictions. By testing these predictions, we may be better able to understand both the proximate and ultimate causation of kin discrimination abilities in a variety of fishes.