Using satellite telemetry data to estimate loggerhead availability to aerial observers in the poorly-understood northern Northwest Atlantic Ocean

Availability bias occurs when turtles are not available to be seen by aerial survey observers, and it can be a substantial source of bias. Without explicit consideration of availability bias, survey line transect methods may be unacceptably biased for sea turtles and other marine animals. In preliminary analysis we estimated loggerhead availability bias from satellite tagging data, and the estimates of availability bias were extraordinarily influential in the estimation of loggerhead abundance from line transect data. We were able to build a robust availability dataset for Long Island through Florida, but we do not have availability data to correct the aerial surveys that are currently being flown from Long Island through Nova Scotia. Satellite-tagging turtles from both directed captures and Canadian pelagic longline bycatch will allow us to collect in-water data on appropriate temporal and spatial scales to estimate stage-specific regional and seasonal abundance and movement rates; and collecting blood for testosterone analysis will allow us to estimate stage-specific sex ratios for this under-sampled population segment.

The objective of this proposal is to collect surface availability data on loggerheads in Southern New England and Southwestern Canada.