Benefits of an Offshore-Intake for Reducing Entrainment and Impingement in Lake Ontario

The potential reductions in entrainment and impingement of an offshore cooling water intake structure (CWIS) were estimated by comparing fish densities at multiple locations to those at an existing offshore intake.  The density of fish susceptible to impingement in a 2.5 km² nearshore area (3 to 36 m water depth) of Lake Ontario was estimated by 329 weekly echo-sounder surveys along twenty 1-km transects during the day and night of June-December 2009, April-November 2010, and April-December 2011.  Species and size of fish sampled acoustically were described from monthly gill net and mid-water trawl catches. Ichthyoplankton density was estimated from 2,678 Tucker trawl samples collected during the day and night of the same years at multiple depths and stations within this area.  Generally, the deepest samples in the water column at offshore locations more than 18.3 m in bottom depth had the lowest ichthyoplankton density, but also had the highest density of fish susceptible to impingement.