Fisheries Research Report No. 1715, 1966

Michigan Department of Conservation
Institute for Fisheries Research Report No. 1715, 1966
The Study of the Population Fluctutations of the Cisco, Coregonus artedi (LeSueur) in Birch Lake, Cass County, Michigan, with Special Reference to the Gill-Net Sport Fishery

By Michael D. Clady

      Introduction- The shallowwater cisco, Coregonus artedi (LeSueur) is found in many lakes of the Great Lakes region and the upper Mississippi River system and northward through the southern drainages of Hudson Bay (Hubbs and Lagler, 1958). This fish formerly was quite common in the Great Lakes themselves, and also is found in many deeper inland lakes where conditions are suitable for its survival. In the Great Lakes, where it is called the “lake herring,” the vertical distribution of the cisco is somewhat intermediate to that of the warmwater fish and the deepwater members of the whitefish family. However, in inland lakes it is a deepwater fish and inhabits the deepest and coldest water available, at least during times of the year when limnological conditions are favorable. The cisco is a pelagic spawner. In late autumn, the adults move out of the deeper water and onto shallow shoal areas where, apparently most at night, the eggs are broadcast over the bottom. The eggs hatch the next spring and the larvae begin to feed on plankton, which they will do for the rest of their lives. The species is relatively short-lived and individuals normally survive about 5 or 6 years.
      Morphologically, Coregonus artedi is a very plastic species, as are many members of the whitefish family. Meristic characters and body proportions vary greatly for the species from lake to lake and even from year to year within the same body of water. Variation is so great and widespread that a large number of populations, 24 to be exact, were recognized as distinct subspecies by Dr. Walter Koelz, who did much of the early taxonomic work with the coregonids in the Great Lakes region (Koelz, 1929, 1931). Later, Hile (1937) found that the differences upon which the subspecific separations were based too narrow, in view of the wide natural variation, and concluded that larger samples of ciscoes would have to be studied before the numerous subspecies could be justified. The present study does not include taxonomy of the cisco because sufficient material was not available. It is felt that the inclusion of this population in the typical inland deepbodied form is acceptable for the purposes of this study.
      Many authors have studied the sometimes violent fluctuations which the cisco populations of the Great Lakes have shown throughout the history of the fisheries there (Scott, 1951; Pritchard, 1931; Smith, 1956; Van Oosten, 1930). Others mention similar, though apparently less violent, changes of cisco populations in inland lakes (Carlander, 1943; Hile, 1936). This study of an inland cisco population deals with such fluctuations over a period of 25 years, with a few minor gaps during this time. The study suffers somewhat because the quality and quantity of data varies considerably over this extended period. Nevertheless, the study is justified simply because it apparently is the first investigation of the cisco which contains some population, growth, and life history data throughout the entire period of population change.