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Mitzner, L. (1994). Management of aquatic vegetation with grass carp in Iowa, 1973-1993. Lake and Reservoir Management. 9:99-100.

Diploid grass carp have been used in Iowa to control aquatic macrophytes for over two decades. Initial introduction occurred at Red Haw Lake in 1973 as part of a research investigation to study the feasibility of macrophyte control. Routine use of grass carp as a fisheries management technique in state-owned lakes commenced in 1975, and by 1979, the general public was permitted to buy and stock grass carp into public waters. Over 700 permits were issued to the private sector the first year the permitting system went into effect. Since 1973, grass carp have been stocked in over 40 state-owned lakes, and since 1979 approximately 2,000 private waters have been stocked. Stocking rate was initially 10 per acre (total lake surface), but more recently the recommended stocking rate was reduced to 5 or less per lake surface acre. Length of grass carp at stocking is recommended at >8 inches in waters containing largemouth bass. Partial control of vegetation by grass carp is rarely attained; normally there is an all-or-none response. At lakes with 100% control of vegetation, there are only minor changes in sport fish populations. For example, fisheries managers reported diminished bluegill recruitment at some lakes with 100% vegetation control. The most common complaint comes from bass anglers who perceive the "weedline" as being greatly reduced. Thus, according to anglers, bass are not nearly as vulnerable to hook and line at lakes with extensive macrophyte control. Overall, sportfishing has not been adversely impacted by grass carp introductions and in most cases catch has increased because of more available access to shore anglers fishing for bluegill and crappie. Grass carp reproduction has not been documented in Iowa waters; however, adults have been caught incidentally (60 lbs per pool) in commercial fishing gear in the Mississippi River bordering Iowa.