The influence of hydrology and waterway distance on connectivity of Chinook salmon in a large river

Adult Chinook salmon navigate in river systems using olfactory cues that may be influenced by hydrologic factors such as flow and the number, size and spatial distribution of tributaries. Thus, river hydrology may influence both homing success and population connectivity. In this study, two methods of multivariate analysis were used to examine the extent to which four indicators of hydrology and waterway distance explained population structure of Chinook salmon in the Yukon River. A partial Mantel test showed that the indicators of hydrology were positively associated with broad scale (Yukon basin) population structure, when controlling for the influence of waterway distance. Multivariate multiple regression showed that waterway distance, supplemented with the number and flow of major drainage basins, explained more variation in broad-scale population structure than any single indicator. At an intermediate spatial scale, indicators of hydrology did not appear to influence population structure after accounting for waterway distance. These results suggest that habitat changes in the Yukon River, which alter hydrology, may influence the basin-wide pattern of population structure in Chinook salmon. Further research is warranted on the role of hydrology in concert with waterway distance in influencing population structure in Pacific salmon