Effects of life stage on the spatial ecology of Chinook salmon (Oncorhynchus tshawytscha) during pelagic freshwater foraging

Chinook salmon (Oncorhynchus tshawytscha) have been observed to spatially segregate based on body size in the marine environment. In their introduced range in the Laurentian Great Lakes, where Chinook salmon support important recreational fisheries, very little is known about their seasonal habitat use, including effects of body size on horizontal and vertical distributions. This study quantified the seasonal home ranges and distributions by depth and temperature of two size classes of Chinook salmon in Lake Ontario using pop-off data storage tags (pDST) from 2014 to 2016 and acoustic telemetry from 2017 to 2020. Moderate overlap occurred between immature (age classes 1 and 2) and sub-adult (age classes 3 and 4) individuals at the 50% home range level, a measure of horizontal segregation, with the greatest segregation during the fall and spring. Depth and temperature occupancy for two immature individuals in fall and winter also differed from those of sub-adults. This study is the first to examine the overlap in horizontal and vertical distributions between Chinook salmon size classes in the Great Lakes and contributes key information on their depth and temperature distributions.