DISTRIBUTION AND ABUNDANCE OF AQUATIC MACROINVERTEBRATES FOLLOWING DROUGHT IN 3 PRAIRIE POTHOLE WETLANDS

We collected aquatic macroinvertebrates in a seasonal, semipermanent, and permanent pothole wetland in southwestern Manitoba, Canada to dete rmine their abundance and distribution following drought in relation t o the prelaying, egg-laying and brood-rearing periods of canvasbacks ( Aythya valisineria). We collected 26 taxa of nektonic macroinvertebrat es of which 6 major groups (Cladocera, Copepoda, Ostracoda, Culicidae, Dytiscidae, Gastropoda) collectively comprised >98% of the total numb er of individuals. The number of nektonic macroinvertebrates peaked du ring the egg-laying period, and crustaceans were the most abundant tax a in all 3 potholes during all 3 breeding periods. We collected 50 fam ilies of emergent insects and several unknown families in the orders C oleoptera and Diptera. Five major groups (Chironomidae, Culicidae, oth er Diptera, Coleoptera, Leptoceridae) collectively comprised >97% of t he total number. Insect emergence increased during the breeding season to a peak during the brood-rearing period. Chironomids were the most abundant emergent insect during all 3 breeding periods and were most a bundant in the permanent pothole. Chironomids collected on artificial substrates also were most abundant in the permanent pothole during all 3 breeding periods. The number of gastropods was greatest during the laying and brood-rearing periods. Following drought, it appeared that macroinvertebrates were abundant and widely distributed in the 3 potho les.