HeardMap: Tracking marine vertebrate populations in near real time

We developed a computer program (HeardMap) to receive, manage, visualise and analyse Argos location data and synchronised archival dive data. This program was used to acquire a relative intensity scale of areas of foraging and non-foraging activity of marine vertebrate predator populations around Heard Island in near real time during the austral summer of 2003/2004. Foraging and non-foraging areas were determined by using HeardMap, and trawl and acoustic samples were collected using the research ship Aurora Australis to measure the prey characteristics in those areas. A total of 226 meso-pelagic predators were tagged on Heard Island over a 2-month period. Most of these animals foraged in an area to the east of the island. The use of HeardMap demonstrated that large numbers of predators of various species could be tracked simultaneously and near-real-time estimates of foraging intensity could be derived. The inclusion of dive data in the data display provided a measure of behaviour embedded in the spatial distribution of the animals.