We recently read this interesting paper on understanding the population structure of blue whales in the southern hemisphere using acoustic data to identify the areas they use.
In order to inform management and conservation decisions, we need to know about the population structure, range and distribution of the species of interest. However, for many species of marine mammal, it is difficult to obtain information on population structure. In the southwest Pacific Ocean the movement and distribution of blue whales is largely unknown. A feeding area has been previously identified off the west coast of New Zealand, but where blue whales go during the winter remained a mystery.
This paper provides some insights on blue whales in the southern hemisphere by monitoring their vocalisations. This involved using passive acoustic monitoring (PAM) devices placed throughout the southeast Indian Ocean and the southwest Pacific Ocean, set to record the frequency range of Australian and New Zealand blue whale calls. The results showed that the two call types occurred in different areas, with almost no overlap. The Australian call type was detected off the west and south coast of Australia while the New Zealand call type was detected off the east coast of Australia and off Tonga. These data suggest that there are two acoustic populations, which are separated by the Australian continent.
This is the first study that has detected blue whale calls in the Tasman Sea and off Tonga and the first to detect the New Zealand call type outside of New Zealand waters. It also identifies potential migration routes in the South Pacific Ocean and in the South Indian Ocean (see image below) which is a great step forward toward better understanding the population structure and range of blue whales in the southern hemisphere.
You can read the full paper here to find out more.