Adaptive line transect survey for harbor porpoises

When surveying for animals that are rare and spatially clumped, adaptive sa mpling has been shown to be theoretically more precise than non-adaptive me thods because the increased number of sightings enables model parameters to be estimated more precisely. Adaptive line transect sampling, developed by Pollard and Buckland (1997), is a technique that permits additional survey effort in areas of high animal density. Computer simulation studies indica te this method is unbiased and more precise than traditional line transect methods. To field test this method, shipboard surveys for harbor porpoises (Phocoena phocoena) were conducted in the Gulf of Maine/Bay of Fundy during August 1996. Both adaptive and traditional line transect surveys were cond ucted on the same day over the same track lines. This field experiment demo nstrated that adaptive line transect sampling was easy to implement and res ulted in more precise and lower harbor porpoise density estimates as compar ed to traditional line transect sampling.