Trackline detection probability for long-diving whales

Long-diving whales such as dwarf and pygmy sperm whales (Kogia spp.) and be aked whales (Mesoplodon spp., Ziphius cavirostris, and Berardius bairdii) a pe often missed on visual line-transect surveys because they do not always surface within an observer's field-of-view. I develop a simulation model to estimate the probability of detecting these species. This model differs fr om similar models in that it more completely considers parameter uncertaint y. Search parameters are estimated from data that were collected on the beh avior of observers using 25x binoculars during cetacean surveys. Whale dive times were estimated from visual observations. Conditional detection proba bilities (given that a previously undetected animal is at the surface withi n an observer's field-of-view) were fitted to observed distributions of rad ial sighting distances. The probability of detecting a whale on the trackli ne, g(0), was estimated from the simulation model. For the given methods (> 50 m ship, 25x binoculars, etc.), the estimates of g(0) are 0.35 (CV=0.29) for Kogia spp., 0.45 (CV=0.23) for Mesoplodon spp., 0.23 (CV=0.35) for Ziph ius cavirostris, and 0.96 (CV=0.23) for Berardius bairdii. These estimates are most sensitive to estimates of vessel speed and the duration of long di ves.