Chinook Salmon and Rainbow Trout Catch and Temperature Distributions in Lake Ontario

We determined the distributions of Chinook salmon and rainbow trout by describing seasonal mean vertical and bathymetric catch depths from 1997 to 2005 using angler creel surveys. We developed and applied a cross-validated model of Lake Ontario temperatures to determine the water temperatures associated with these distributions. During April, Chinook salmon and rainbow trout were found nearshore at a bathymetric depth of 20 m. However, rainbow trout were caught at shallower vertical depths (4 to 6 m) than Chinook salmon (8 to 10 m). Both species moved deeper and farther offshore during May, June, and July. Vertical catch depths were similar, but rainbow trout were found further offshore (40 to 65 m bathymetric depth) than Chinook salmon (35 to 50 m bathymetric depth) during June, July and August. During September, Chinook salmon moved closer to shore (25 to 35 m bathymetric depth) and to shallower depths (9 to 12 m), consistent with river mouth staging associated with spawning. Rainbow trout remained offshore (45 to 60 m bathymetric depth) in deeper water (11 to 16 m). The species occupied significantly different spatial habitats during April, August, and September. Mean catch temperatures of both species were similar and increased seasonally to 13 to 14 °C during August and September. Rainbow trout were caught at cooler temperatures than Chinook salmon during June and July. The estimated temperature distributions agree with independent field studies but are different then previously assumed in bioenergetic models.