Density estimator for strip transects when animals show directional movement and observation speed is slow

A strip transect population density estimator and its variance are presented. These take into account stochastic survey velocity as well as stochastic swimming velocity and non-random swimming direction of the surveyed animals. The estimator is mainly of interest for surveys of animals with a directional swimming behaviour and swimming velocities similar to the survey velocity, such as those carried out by divers or remotely operated vehicles.