Gray whale visual sightings from shore 2014-2015

Original provider:
Regina A. Guazzo, Scripps Institution of Oceanography

Dataset credits:
National Oceanic and Atmospheric Administration, Southwest Fisheries
Science Center

Abstract:
During the eastern North Pacific gray whale 2014–2015 southbound
migration, acoustic call recordings, infrared blow detections, and visual
sightings were combined to estimate cue rates, needed to convert
detections into abundance. The gray whale M3 acoustic call rate was 2.3–24
calls/whale/day with an average of 7.5 calls/whale/day over the entire
migration (southbound and northbound) and showed a positive trend from
30 December–13 February. The infrared camera blow rate averaged 49
blows/whale/hour over 5–8 January. With a call rate model, we estimated
that 4,340 gray whales migrated south before visual observations began on
30 December, which is 2,829 more gray whales than used in the visual
abundance estimate. This finding highlights the usefulness of cue rates to
increase precision in abundance estimates. We suggest that visual
observers increase their survey effort to all of December to verify gray
whale abundance corrections. Probability of detection of a whale blow by
the infrared camera was the same at night as during the day. However,
probability of detection decreased beyond 2.1 km offshore, whereas visual
sightings revealed consistent whale densities up to 3 km offshore. We
suggest that future infrared camera surveys use multiple cameras
optimized for different ranges offshore.