Sea lampreys are aquatic invaders that contributed to the collapse of lake trout populations in the Great Lakes.  Control efforts have successfully reduced lamprey populations and their impact on fishery resources. 

John Netto, Green Bay Fishery Resources Office, presented a review of sea lamprey mortality in the 1836 Treaty Waters of The Great Lakes at the spring meeting of the Sea Lamprey Integration Committee in Ann Arbor, Michigan. 

As part of the stock assessment process in the 1836 treaty waters, biologists estimate sea lamprey induced mortality on lake trout.  This source of mortality is a major component of total lake trout mortality and has implications on the health of lake trout stocks and the fisheries they support. 

Netto’s presentation provided a review of how sea lamprey induced mortality is estimated from wounding data collected from fishery monitoring and survey data.  The presentation also reviewed sea lamprey mortality levels and compared this source of mortality to recreational and tribal commercial fishing mortality.  

Currently, sea lamprey mortality exceeds fishing mortality in Lakes Michigan and Superior.  In Northern Lake Michigan, sea lamprey mortality increased dramatically in 2003 and remains higher than levels observed over the previous twenty years. 

Sea lamprey mortality levels were very high in Lake Huron during the 1990’s, but they have been low since 1999 due to increased control activities in the Saint Mary’s River.