Tracking marine animals

Deploying a net from the trawl deck of the Aurora Australis
Deploying a net from the trawl deck of the Aurora Australis (Photo: Steve Nicol)
Female fur seal tracks around Heard Island for 20 individuals for a single foraging trip each between the 20 December 2003 and 11 January 2004. Dots represent the Argos locations with the temporal sequence shown by linking the dots with straight lines.Area usage grid of the tracks displayed in the left hand figure. The relative amount of time that a number of animals spent in a given area is represented by the colour where blue is low and red is high.

Building a picture of who is eating whom in the Southern Ocean and how much is being eaten — a food web — will help us to better manage fisheries resources.

In the summer of 2003–04 an expedition to Heard Island used software called HeardMap to do just this.

HeardMap looks at two data sets at the same time:

  1. The movements of seals and penguins tagged with satellite transmitters to identify their foraging areas in near real time.
  2. The diving location of seals and penguins using dataloggers which record diving behaviour.

HeardMap then gives precise locations and depths in near-real-time of the key prey species in the diet. Trawl and acoustics samples are then collected from a research vessel.

Data collected in near-real-time allows scientists to examine and compare foraging and non-foraging areas for a number of seals and penguins. From these data we will be able to improve our predictions of how fisheries might affect the predators that are also dependant upon these resources.

The use of HeardMap shows that large numbers of predators of various species can be tracked simultaneously and near-real-time estimates of foraging intensity can be predicted. The inclusion of dive data provides a measure of behaviour embedded in the spatial distribution of the animals.