A contagious disease of salmon, possibly of virus origin
Production records for 1885, 1891–1908, and 1929–49, indicate cyclic fluctuations for several important species of fish. The average annual take (all species) of 3,582,000 pounds in 1929–49 was 3,503,000 pounds below the 1891–1908 mean of 7,085,000 pounds. Decline in the output of lake herring alone from 5,841,000 pounds in 1891–1908 to 1,070,000 pounds in 1929–49—a drop of 4,771,000 pounds—more than accounted for the decrease. For species other than lake herring the combined output increased from 1,244,000 pounds in 1891–1908 to 2,512,000 in 1929–49—a rise of 1,268,000 pounds. The 1929–49 fluctuations of abundance (as estimated from records of catch per unit of effort) were considerable for all principal species. In the late years of the period, lake trout were scarce as the result of sealamprey depredations, but the abundance levels of whitefish, lake herring, and walleyes were extremely high; at the same time the smelt was showing good recovery from the disastrous 1943 mortality. With certain exceptions, correlations between fluctuations of fishing intensity and the abundance of individual species were low, probably because most operations are based on several species and hence not ordinarily sensitive to changes in the abundance of a particular one. A combination of intensive fishing and high abundance of three principal species carried the production to 5% million pounds in 1947 and the modern record high of between 7% and 8 million pounds in 1948 and 1949. With this prosperity has developed a most difficult situation arising from friction between local commercial fishermen and newcomers from other areas and from the activities of sport fishermen and resort owners who believe that drastic restrictions on commercial fishing will insure a perpetual high level of abundance of walleyes. Statistics for 1950 are given in a supplement.