Components of hunting mortality in ducks : a management analysis

This study was conducted to evaluate waterfowl harvests on the Delta Marsh, Manitoba, under a variety of options utilizing a modified predator-prey model. The study involved monitoring of ducks and hunters to examine key components of waterfowl mortality. Seven hypotheses were formulated involving the relationships between duck vulnerability by species and hunter effort, factors determining effective bag size, hunter effort, effects of weather on kill, and whether or not hunters are selective. Aerial surveys and experimental hunts were conducted and kill statistics gathered on the Pasquia and Delta Marshes in Manitoba to evaluate predictions from the hypotheses. The analysis of field data revealed that duck vulnerability is negatively proportional to hunting effort and that ducks are most wary when hunter effort is greatest. Hunters were afield in largest numbers during periods of high duck density. Hunters did not shoot selectively and crippling losses approximated one-third of the birds shot. Weather had little influence on the kill; bird population size and hunter effort were more important determinants of hunter success. Distribution patterns of ducks were clumped relative to hunting areas, and the probability of mortality for an individual duck was observed to decrease with increasing flock size. Handling time per bird downed did not limit achieved bag size whereas time between encounters was found to be independent of population size and resulted in a non-linear, kill-density relationship. Field results were incorporated into the predator-prey model and management schemes involving population size, hunter effort, and season length were evaluated. Simulation results revealed that Mallard and Lesser Scaup harvest are not greatly affected by increased hunter effort and that season length and population size strongly influence harvest. Shortened seasons are recommended if kill reductions are desired for Mallard. Lesser Scaup require no special regulations whereas Canvasbacks require short seasons (less than 2 weeks) during times when populations exceed 5000. The predator-prey model is recommended for in-depth analysis of local regulations whereas multi-variate statistical models may be more useful in forecasting yields on a regional level.Science, Faculty ofZoology, Department ofGraduat