CANVASBACK MORTALITY FROM ILLEGAL HUNTING ON THE UPPER MISSISSIPPI-RIVER

To quantify the consequences of local hunting on illegal kill of canva sbacks (Aythya valisineria), we studied the behavior of hunters on a 6 46-ha area open to duck hunting (closed to canvasback hunting) on Lake Onalaska, Navigation Pool 7, Wisconsin, during the 1991 and 1992 wate rfowl hunting seasons. Law enforcement officers observed 258 hunting p arties for 419 hours. Of 94 hunting parties encountering canvasbacks, 41 (44%) shot at the ducks on 56 occasions, or 27% of 207 encounters o bserved, Based on a ratio estimator, there were 790 (95% CI = 376) att empts to shoot at canvasbacks on the Lake Onalaska study area during 1 991 and 837 (95% CI = 390) during 1992. Mortality of canvasbacks, excl uding crippling loss, was estimated to be 128 during 1991 and 166 duri ng 1992. Thus, total canvasback losses may be higher than currently es timated on a flyway or national basis. This estimating technique offer s a promising method for enumerating hunter take of protected and lega l species.