Parasitic Phase of the Sea Lamprey (Petromyzon marinus) in Lake Ontario

Abstract

Sea lamprey produced in other areas of Lake Ontario appeared to be responsible for significant levels of predation on target species of the eastern outlet basin. The life history of the lamprey is simple with only one parasitic generation present in the lake during the feeding period. Wound frequencies on gillnetted whitefish were influenced by season, fish size, gillnet set duration, and a large random error component which suggested a contagious distribution. Scar frequencies were influenced by fish age and indicated improved survival of whitefish when fish weight exceeded lamprey weight by 43 times. Lamprey impact on the whitefish stocks would probably have been more important at lower fishing intensities. The lamprey may have been prey limited, and size and species preference were probably such that lake trout and burbot were not buffered against sea lamprey by white suckers or whitefish. The analysis favored the view that lamprey were innocuous in 19th century Lake Ontario by reason of prey size and density, but climatic and other environmental effects could also have been important.Key words: sea lamprey, lake whitefish, Lake Ontario