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CHAPTER 4: ECOLOGICAL TRENDS OF SELECTED FAUNA IN THE UPPER MISSISSIPPI RIVER partly due to removal of paddlefish from the commercial species list by Iowa, Wisconsin, and Minnesota. Grass carp (Ctenopharyngodon idel/a), an exotic, was first observed in the Missouri portion of the Mississippi River in 1975 (Ras- mussen, 1979). By 1991, there were nearly 17,000 pounds of grass carp harvested commercially. Changes in age and species composition of commer- cial fish species are extremely difficult to document, espe- cially if commercial halVest statistics are used to discern changes. Although the total commercial catch of fish appar- ently has not changed significantly in the last 100 years, the abundance of several species has changed dramatically. The most significant change in tenns of abundance has been the increase in carp (C.vprinus carpio). Carp was not even reported from the Mississippi River until 1883 (Cole, 1905). In 1894, there were 453,000 pounds of carp (approximately 3 percent of the total harvest) harvested from the river, and by 1899 the carp catch had risen to 3.1 million pounds. For the 25-year period from 1953 to 1977, an average of 5,2 million pounds of carp (or 47 percent of the average total annual harvest) was harvested annually (Kline and Golden, 1979). The dramatic rise in carp was paralleled by a concur- rent decline in native buffalo (letiobus spp.) fishes. In 1894, buffalo made up 43 percent of the total catch. For the 25-year period (1953-1977) summarized by Kline and Golden (1979), buffalo made up an average of 22 percent of the total catch. Aside from the documented competition with carp, Coker (1930) theorized that reclamation of the adjacent floodplain for agricultural purposes eliminated large shallow pools used by buffalo for spawning. Harvests of carpsuckers (Carpiodes spp.), suckers (Catostomidae), sturgeons, paddlefish, and American eels have also declined markedly. There are several reasons for the decline of these and other noncommercial species. Con- struction of the Keokuk Dam in 1913 and the oavigation dams in the 1930's is thought to have blocked or impaired the spawning movements of such species as the skipjack herring (A/om chrysochloris), lake sturgeon (Acipenser fu/- vescens Rafinesque), paddlefish (Po/yadon spathu/a), and American eel (Anguilla rostrata). The manner in which these navigation dams were operated (Le., winter draw~ downs) in the 1930's and 1940's could also have contrib- uted to the diminished abundance of some species. The UMR paddlefish population could now be in jeopardy because dams blocked their movements and because of a lack of suitable gravel beds for spawning. The plight of pad- die fish may be indicative of the fact that juvenile paddlefish have not been readily collected in recent fishery surveys. The collection of a juvenile paddlefish, in the upstream pools particularly, is a rare occurrence. There are more than 3,000 river training structures (i.e., wing dikes, closing dams) on the UMR, which have drastically altered fish habitats. Their construction has led to a narrowing and deepening of the channel, thus degrading main channel spawning habitats for such species as suckers, 45 sturgeons, and paddlefish (U.S. Anny Corps of Engineers, 1974; Upper Mississippi River Basin Commission, 1981). Lubinski and others (1981) reported that some river areas had degraded by as much as I I feet after construction. Although there are no substantiating data, fishery biologists generally believe that the decline of the federally endan- gered pallid sturgeon (Scaphirynchus a/bus) is attributable to construction/channelization of the open river below St. Louis, Missouri. A comprehensive review of the status of UMR fishes perfonned by Smith and others (1971) and Van Vooren (1983) noted approximately 134 species of fish present on the UMR. The "Distribution and Relative Abundance of Upper Mississippi River Fishes," previously prepared by Van Vooren (1983). is now under way by the UMR Conser- vation Committee (Pitlo and others, 1995). Although the total number of fish species on the UMR may not have changed significantly, the abundance of many species has diminished in the last 100 years. Fish species historically found on the UMR main stem, and whose current status indicates a need for special attention, are listed in table 4-2. These UMR fish species have received special status either through the Federal Endangered Species Act, as amended, or through special State designation. CONCLUSIONS Most of the 39 mussel species recorded from the UMR main stem prior to human settlement are still present, but they have an uncertain future. Five species present at the turn of the century are no longer known to occur on the UMR. Long-tenn trends in mussel population indicate that additional mussel species are likely to disappear from the UMR mussel assemblage unless appropriate management actions are implemented soon. Poor water quality, stream- bed alteration due to navigation improvements, zebra mus- sel competition. and floodplain development are the preem- inent threats to maintaining a healthy mussel assemblage. These problems must soon be addressed on a systemwide scale if a healthy, self-sustaining mussel population is to be maintained. The majority of attention now given to UMR mussels is from a regulatory (i.e., commercial harvest) and impact perspective (i.e., pennit review under Section 404 of the Clean Water Act). Greater emphasis on monitoring and basic research is sorely needed in order to determine future management requirements. UMR fish populations remain healthy in spite of sig- nificant habitat changes over the last 100 years. Thus far, there has been no major extirpation of species. The most significant change in UMR fishes over the last century appears to have been a change in abundance for several spe- cies, Some species, such as lake sturgeon (Acipenser fu/ve- seens), are much less abundant. Competition from the common carp (Cyprinus carpio) has also been a significant