OPPORTUNISTIC RESPONSE OF A BENTHIC MIDGE (DIPTERA, CHIRONOMIDAE) TO MANAGEMENT OF CALIFORNIA SEASONAL WETLANDS

The effects of seasonal flooding on larvae of Chironomus stigmaterus S ay were studied in 12 managed wetlands of the Sacramento-San Joaquin R iver estuary, California. Six pairs of wetlands were flooded artificia lly on 5 and 19 August; 2, 16, and 30 September; or 14 October 1991. O ne member of each wetland pair was dominated by pickleweed, Salicornia virginica L., and the other by alkali bulrush, Scirpus robustus Pursh . Densities of midge larvae were significantly higher in wetlands floo ded earlier than later. The numerical patterns exhibited by C. stigmat erus populations suggest opportunistic responses. Midges thrived in ha bitats 1st flooded in August, yet such habitats would not naturally ex ist in the California Mediterranean climate because the rainy season d oes not begin until late autumn. Although this midge probably evolved in freshwater habitats, it readily colonized habitats dominated by pic kleweed, a salt march plant. Populations of the beetle Berosus ingemin atus d'Orchymont also were higher in pickleweed wetlands during autumn . Because C. stigmaterus larvae are an important food resource for dab bling ducks, their opportunistic response to the artificial conditions in California seasonal wetlands has benefits in terms of waterfowl ma nagement.