After the collapse of the commercial fishery for lake trout (Salvelinus namaycush) in Lake Michigan in the late 1940's, the further decline of the population was traced by records of numbers of small lake trout (mostly 11 to 16 inches in total length and 3 to 5 years old) caught in small-mesh nets of the chub (Coregonus \[= Leucichthys\] spp.) fishery. By 1951 the estimated abundance of these lake trout in lower Lake Michigan was only about 4 percent of their abundance prior to the invasion of the sea lamprey (Petromyzon marinus). This remnant of the population declined severely in subsequent years to a point near extinction by 1955. In April-July 1955 only 8 lake trout were caught in 5 1/2 million linear feet of gill net.
Statistics of the lake trout and chub fisheries in State of Michigan waters of Lake Michigan for the years 1929–1954 give no indication that the destruction of small lake trout in the chub fishery had any effect on the later abundance of lake trout of commercial size, or that this destruction was a significant factor in the collapse of the lake trout fishery.
Lake trout were brought near extinction by lethal attacks of the sea lamprey and by the near or perhaps complete failure of natural reproduction in 1949 and subsequently.
Comparisons in 1949 and 1950 of numbers of legal-sized lake trout caught in large-mesh nets with numbers of small fish taken in chub nets showed that both large and small lake trout declined over the same period, and that by these years the decline may have been greater among small than among legal-sized fish.