The covered area given for each stratum is calculated from a strip width equal to the maximum distance at which a sighting wasreported and multiplied by the average probability of detection over that strip, g(x). The estimated coverage is calculated from a strip width equal to the maximum distance at which any sighting was reported in each year, minus the left truncation distance. The strip is then multiplied by the linear survey effort (km) and the average probability of detection over that stratum, g(x), to give the approximate survey coverage.