Ciscoes have a unique ecological role in the Great Lakes
Cisco is not a true herring but it is closely related to the lake whitefish.
The cisco, formerly known as “lake herring,” has historically yielded larger commercial harvests than all other species combined in Lake Superior. During the first half of the 1900s, ciscoes frequently constituted 25 percent to more than 50 percent of commercial production in the Great Lakes. From 192-1961, the average annual commercial catch of lake herring in Lake Superior was nearly 12 million pounds, contributing 62.4 percent of the total U.S. take for the Great Lakes. Since the late 1960s that number has been on the decline. The largest populations of lake herring in the Great Lakes are now found in Lake Superior. In recent years the Lake Superior cisco population has fluctuated between low and high class production.
The cisco can be found in water columns where it feeds on small aquatic animals called zooplankton. Early settlers of the Great Lakes region thought that because of its schooling nature, it was related to the ocean herring. Ciscoes are found in cold lakes throughout Canada and northern United States. The cisco is different from its cousin, the lake whitefish, because it filters water in the water column for zooplankton. The lake whitefish lives near the bottom and thus feeds on organisms near the bottom of the lake.
Overfishing, habitat degradation and invasive species were thought to reduce the abundance of cisco throughout the Great Lakes in the 1960s. Cisco were once an abundant fish in the Great Lakes that served as both a commercial and forage fish. In recent years the most abundant populations of cisco exist in Lake Superior and northern Lake Huron with remnant populations in Lake Michigan. When the cisco disappeared, the predominant forage fish that took its place was the non-native alewife. The alewife supported the salmon fishery in the Great Lakes but had negative qualities such as high levels of thiaminase which interferes with reproduction of trout and salmon. The alewife also preys on many of our native larval fish and thus retards recruitment.
The cisco, which is a native species, does not share these negative attributes of the alewife. In recent years the alewife population has dropped. This opens a window for the native cisco to be reintroduced into areas where it no longer exists. Some issues that need to be resolved are the development of hatchery facilities that can produce large numbers of cisco and what genetic lines should be used in this rehabilitation effort.
To partially address this concern, the Lake Michigan Committee of the Great Lakes Fishery Commission formed a Native Planktivore Task Group to scope out issues related to the restoration of native planktivores in Lake Michigan. The charge is to develop a “white paper” that articulates the candidate species for consideration, the impediments as well as opportunities for reintroduction or recovery, specific management actions that can foster both and a summary of research needs. Michigan Sea Grant and Michigan State University Extension serve on this task group and have contributed to the section on cisco.