Evidence of a novel reproductive tactic in female kokanee Oncorhynchus nerka

Body composition analysis confirmed that egg development and reproductive senescence were delayed in silver female kokanee Oncorhynchus nerka (a small proportion of female kokanee exhibit extreme prespawning waiting and are called 'silvers' because of their colouration) relative to that of red female kokanee (most female kokanee exhibit this 'normal' phenology and are called 'reds'). Silver females were also smaller and younger than red females. A simple life-history model with two size thresholds is proposed to account for the observed body size and age differences. Adoption of the silver tactic by small females is proposed as a means to minimize intrasexual competition.