Impingement Rates at Four Intakes at Two Paper Mills Located on the Wisconsin River

An impingement study was conducted from 2012-2013 at two paper mills located in close proximity on the Wisconsin River.  Impingement sampling was conducted at four differently configured intakes over five consecutive days each month from October 2012 to September 2013.  Impinged organisms were collected every 24-hours and were identified to the species, weighed, measured, and their condition assessed (alive, prior-dead, etc.).  Both the rates of impingement and the total numbers impinged varied substantially between the intakes; two of the four intakes accounted for 99% of the fish impinged. Eighty percent were collected on two separate months (April and August).  Overall the most commonly impinged species was channel catfish (60%). Based on length, the majority of this species consisted of fish in the 1 to 2 year age classes.  Additionally, non-forage species in the early age classes were commonly impinged.  Results of this study indicate a high seasonality in impingement rates and suggest that intake configuration has a substantial impact on impingement rates.  Aspects of the different intakes that affect impingement rates will be considered.