Correcting for Visibility Bias in Strip Transect Aerial Surveys of Aquatic Fauna

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Abstract
We develop methodology for correcting for visibility bias by calculating and applying survey-specific correction factors in strip transect aerial surveys of aquatic fauna and incorporating their associated errors into the population estimate. The technique is applicable at all densities of the target species. Perception bias (the proportion of groups of the target species that are visible in the transect yet missed by observers) is corrected for using a modified Peterson estimate calculated for each of 2 teams of 2 observes with 1 team on either side of the aircraft. Within a team, each observer reports their uncolluded observations into a separate track of a 2-track tape receptor, so that after the survey, each group can be characterized as being seen by only 1 (specified) or both members of the team. A correction factor is also suggested to standarize for the proportion of animals that are unavailable to observers because of water turbidity.