Bottom Trawl Explorations in Lake Superior, 1963-65

Six exploratory fishing cruises, totaling 122 operating days, were made by the research vessel Kaho from November 1963 to October 1965. Most of the exploratory operations were in the central and eastern portions of the lake; however, limited surveys were made in the western area during 1965. This study is the first attempt to assess the potential for commercial bottom trawling in Lake Superior. Suitable bottom for trawling was found along about 65 percent of the south shore. Over 74 percent of the total catch by the Kaho were chubs (Leucichthys spp.) followed by American smelt (Osmerus mordax), 10 percent; suckers (Catostomus spp.), 6.5 percent; and lake trout (Salvelinus namaycush), 3 percent. Commercially significant catches, 250 pounds per one-half hour, of chubs were taken on every cruise and these fish, even if used mainly for animal food products, could apparently support a limited trawl fishery. Smelt, suckers, and common whitefish (Coregonus clupeaformis) were caught occasionally in commercially significant quantities and could greatly supplement production efforts. Most lake trout were caught in specific geographic areas and appeared to be segregated by size in specific depth zones. Abundant concentrations of small trout could easily be avoided after being located by fishing certain depths. With proper care, most trout were returned to the water alive. The alewife (Alosa pseudoharengus), which is now the basis of a growing trawl fishery in Lake Michigan, and lake herring (Leucichthys artedi) were not taken in significant amounts during the study.