The White Sucker Population of South Bay, Lake Huron, and Effects of the Sea Lamprey on It

Abstract

Information on ecology and dynamics of white suckers, Catostomus commersoni (Lacépède), in South Bay, Lake Huron, was obtained from experimental fishing over more than a decade and from a tagging program in 1955 and 1956. (A total of 1667 suckers were tagged and 8% of them were subsequently recovered.) The fish moved about extensively in the bay, minimal distance travelled averaging 3.8 km during a summer. Nevertheless, it was necessary to divide the bay into discrete fishing areas for calculating population and mortality estimates. The length–weight relationship of adult suckers in June was W = 5.883 × 10⁻⁴ L^2.92262; where W is weight in pounds and L is fork length in inches. Growth averaged only about 7.6 mm/year, and an annulus was not formed on the scales every year. In 1956 the population may have amounted to about 160,000 adult white suckers, or 23 fish per hectare or 17.5 kg/hectare, for the part of the bay less than 36 m deep. The exploitation rate appeared to be less than 2%. The annual survival rate of suckers larger than approximately 38 cm appeared to be about 70–75% decreasing with size of fish. Although it is not known if the size of the population has changed, the size composition changed between 1953 and 1964 through the loss of larger fish. Marked changes in the fauna of South Bay subsequent to the late 1940's include the invasion of the sea lamprey, Petromyzon marinus Linnaeus, and the alewife, Alosa pseudoharengus (Wilson), the disappearance of the lake trout, Salvelinus namaycush (Walbaum), and the decline of the population of the cisco, Coregonus (= Leucichthys) artedii LeSueur. The loss of the larger fish in the white sucker population was probably caused by the sea lamprey, for it occurred after the destruction of the lake trout population and corresponded with increased incidence of lamprey scarring of suckers.