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Techniques to encourage wigeongrass growth in these impoundments were refined during the seventies and eighties. Wilkinson (1970) noted steadily increasing frequency of wigeongrass for 3 years in a newly constructed South Carolina impoundment, where brackish water was held at 0.61 m except during February, when it was drained. Morgan (1974) and Morgan et al. (1976) recommended raising water levels slowly during the growing season or taking in seawater during spring tides, draining ponds every two years, and keeping salinities around 8.75 to 17.5 g/L to discourage possible macrophyte competitors. Heitzman (1978) noted that, after several years of stable water levels, silt and detritus accumulations greater than about 4 cm will not provide a good rooting medium for wigeongrass, and expose stands to rapid elimination by wave action. At that time, it is necessary to temporarily drain impoundments to a moist-soil condition to compact and oxidize bottom substrates and restore productivity.

For ponds in the 5.0-20.0 g/L salinity range, Prevost (1987) recommended (1) lessening acidity by lowering water during March to May (for 2-8 weeks) to levels that keep the bottom saturated but free of surface water; (2) stabilizing soils and reducing turbidity by lowering water levels for 1-2 weeks in late spring or early summer to 25-46 cm below the bottom surface; (3) reflooding ponds to 15-20 cm; and (4) controlling algae by gradually raising water levels to 46-76 cm in summer and early fall while maintaining water circulation. For ponds with salinity in the 20.0-30.0 g/L range, he recommended similar techniques - but for ponds in this range that are dry for several years, he suggested trying to raise bottom substrate pH by changing water 2-3 times at 4-6 week intervals during the growing season. For ponds with > 30.0 g/L salinity, management involves tidal flooding in early spring and diluting with fresh water later in the growing season. Recent observations on wigeongrass in coastal California impoundments have indicated that acidity in heavy clay soils can best be reduced by very slow reflooding rather than a regime of rapid reflooding and flushing (B. Smith, California Department of Fish and Game, personal communication). Additional details are available on construction, management, and maintenence of coastal wigeongrass impoundments (Epstein et al. 1986; South Carolina Sea Grant Consortium 1987).

A different situation for wigeongrass management exists in the wetlands of the Great Basin, where soil salinities are often too high to support the plant. Here, Salicornia-dominated salt flats lying near sources of freshwater inflow are diked and flooded with 45-60 cm of fresh water. After an initial growth of Chara, impoundment water levels are maintained at about 35 cm to maintain wigeongrass and other submersed macrophytes that prosper under reduced soil salinties (Kadlec and Smith 1989).

At least in the southeastern United States, an added benefit of dewatering wigeongrass ponds to substrate levels is the growth of clumps of emergent hydrophytes that later reduce the destructive effects of wave action (Swiderek 1982). Heitzman (1978) noted that failure to harvest muskrats can result in total loss of such emergents but that far more damage to submersed macrophytes can occur when burrowing causes dike damage that drains impoundments.

Techniques to harvest and plant wigeongrass have been known for many years. To obtain drupelets, McAtee (1915) suggested gathering them from the upper part of plants to reduce unwanted material and allow for better air circulation. He also recommended wet cold storage if drupelets are not planted immediately and soaking them thoroughly before planting so they will sink. Terrell (1923) recommended planting 5 bu/acre (4.4 hL/ha), either rhizomes or whole plants, in brackish or saline water 0.3-1.5 m deep. Joanen and Glasgow (1965) stated that the general techniques of Martin and Uhler (1939) for harvest, storage, and planting of submersed hydrophytes will work for wigeongrass. Stands can be established by imbedding drupelets or leafy stems in clay balls and dropping them overboard (Steenis 1939) or by merely scattering plants on the water, preferably in spring (Neely 1962). Donnelly (1968) successfully planted wigeongrass with 15 cm^2 plugs of bottom substrate, presumably containing rhizomes, roots, drupelets, and portions of stems.

Gore (1965) noted good spring germination of fall-collected drupelets stored in brackish water in a refrigerator at 0.5 degrees C. Recent work by Seeliger et al. (1984) and Koch and Seeliger (1988) suggested that better germination of wigeongrass drupelets results when storage conditions are geared to the general environmental conditions of the wetland where the drupelets are collected and the life-cycle characteristics of the plants in that wetland.

Information on artificial or induced establishment of submersed hydrophytes was reviewed by Kadlec and Wentz (1974). They provided lists of plant suppliers, techniques for propagule harvest, storage, and planting, and methods for site preparation.

The impoundment of coastal wetlands to produce wigeongrass and other plants has created favorable habitat for many other organisms besides wintering waterfowl. Nevertheless, the desirability of impounding more tidal wetlands has come under increased scrutiny in some states because these habitats are unsuitable for certain economically important marine fish and other organisms (Gilmore 1987). Overall, however, it is likely that water pollution, dredging, and changes in water regimes caused by dam operations have been far more damaging to marine biota than have these waterfowl impoundments.