A Case History of Sea Lamprey Control in Lake Michigan: 1979 to 1999

Abstract

The sea lamprey ( Petromyzon marinus) control program, along with the stocking of native fish species, the introduction of Pacific salmon, and the application of regulations controlling harvest, has allowed the socioeconomic and biological recovery of the Lake Michigan fishery which has been described as “spectacular.” The program is now instrumental in maintaining today's fish community structure. Initial treatment of Lake Michigan tributaries with the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) reduced the number of spawning-phase sea lampreys by 85% and resulted in a noticeable recovery of the Lake Michigan fishery by 1979. Prior to 1979, sea lampreys were present in 115 of the 511 tributaries of Lake Michigan. Sea lampreys were found in four additional streams between 1978 and 1999. The greatest number of parasitic-phase sea lampreys are produced in 34 streams tributary to Lake Michigan. Between 1960 and 1999, 730 treatments were conducted in 113 Lake Michigan tributaries. The six remaining streams were not treated because few sea lampreys were present. The average number of streams treated annually declined from 21 during 1970–1979 to 12 during 1990–1999. Thirty eight percent less TFM (active ingredient) was applied annually, on average, in 1990 to 1999 (192 kg/m 3 of stream discharge) than in 1960 to 1969 (310 kg/m 3 of stream discharge). Barriers specifically constructed or modified to block migrating sea lampreys are currently found on 12 Lake Michigan streams. An additional 27 potential barrier sites have been identified on Lake Michigan streams. The estimated numbers of parasitic-phase sea lampreys in Lake Michigan between 1977 and 1999 ranged from 32,000 (1979) to 105,900 (1998). The incidence of fresh sea lamprey wounds on lake trout ( Salvelinus namaycush) in Lake Michigan was generally less than five per 100 fish in most years since 1971. Sea lampreyinduced mortality increased steadily in the 1990s, especially among large lake trout. Most mortality was in northern Lake Michigan where lake trout are more likely to be attacked by sea lampreys because of the large sea lamprey population.