Southern right whale survey in the South Pacific

WorldView-2 archived images at a resolution of 0.46 m/pixel of August 2020 were used for the survey.

In a first step, the SPACEWHALE algorithm scanned the satellite imagery for the presence of whales.

Subsequently, experts verified whether objects detected by the algorithm were in fact whales to exclude confusion with for example boats, rocks or waves.

Boat-based surveys of whales in the area were carried out twelve hours earlier.

Not only adult whales could be detected and identified in the satellite imagery but also calves. Overall 113 definite adult southern right whales and 58 calves were counted on 17 August 2020 in the survey area.

The number of whales detected by both methods were equivalent despite the 12-hour difference between the time of data collection. The number of calves detected by satellite was slightly lower than determined in boat-based surveys. This was likely due to the algorithm missing calves that were completely concealed by their mothers during the snapshot survey. Use of higher resolution images (~ 0.30 m/pixel) may improve detection of calves that are not fully hidden under their mothers.

The study at Port Ross could prove that satellite-based surveys are well suited to count large whales in remote areas. They may serve to complement existing data and to investigate and fill existing data gaps.