High rates of consecutive spawning and precise homing in Sakhalin taimen (Parahucho perryi)

摘要

The frequency of reproduction and homing success are crucial in determining the lifetime reproductive fitness of iteroparous salmonids. We examined consecutive spawning and homing by Sakhalin taimen (Parahucho perryi), one of the least-studied iteroparous salmonids. The average consecutive return rate was 69.5%, the highest ever reported for an iteroparous salmonid. The consecutive return rates were highest for large spawners, females, and individuals with active inter-tributary movements in the preceding year. We estimated tributary-scale repeat homing rates to be 50-87%, which was significantly higher than expected by chance alone. The repeat homing rates were higher for spawners that entered tributaries with more abundant spawners in the preceding year, which is consistent with the pheromone hypothesis because the abundance of spawners in a tributary is expected to correlate to the concentration of chemical homing cues emanating from offspring in the following year. These extremely high consecutive return and homing rates likely facilitated local adaptation over evolutionary time scales and have contributed to population stability in this river system. These same traits, however, may impede species recovery following habitat restoration efforts within the species historic range (e.g. dam barrier removal or improved passage) due to their limited rate of dispersal.