In order to sustainably manage the commercial fisheries in the waters surrounding the Heard Island and McDonald Islands (HIMI) Marine Reserve, it is necessary to understand the HIMI marine ecosystem and ‘food web’.
An understanding of the food web and the factors driving it will enable managers to make informed decisions about finding a balance between the needs of marine predators and the demands of commercial fishing activities.
The HIMI food web
Understanding how the food web functions requires information about:
- the life cycles of the fish species targeted by the fishery (Patagonian toothfish and mackerel icefish) – their life expectancy and how many eggs and young fish are produced each season;
- the marine mammal and bird species eating those fish – how much they require to feed themselves and their offspring; and
- where the fish occur, and where the feeding activities of marine mammals and birds take place.
In an attempt to obtain such information, an ambitious 'ecosystem-scale' study, involving concurrent terrestrial and marine research, was undertaken at HIMI over the summer of 2003/04.
The aim of the study was to gain information about the feeding habits of the key predators based on Heard Island – those that consume the most food from the surrounding waters – macaroni penguins, king penguins Antarctic fur seals.
A land-based team placed tailor-made miniaturised electronic tags, processors and loggers on over 250 animals, allowing their movements to be tracked via satellite, and providing a picture of their foraging activity.
Specialised software developed by the Australian Antarctic Division (AAD) provided close to real-time access to this foraging data, allowing a marine team aboard the marine research vessel Aurora Australis to take biological samples and measure physical characteristics of the feeding areas shortly after the seals and penguins were there.
Faeces samples were collected when the animals returned to the island to give a comprehensive assessment of diet, which will be determined using a new genetic technique developed by AAD scientists.
Black-browed and light-mantled sooty albatross were also tracked over the summer, to determine whether their foraging range overlaps with areas fished by longline vessels. The albatross were observed to travel thousands of kilometres in week-long foraging trips from Heard Island.
The vast amount of data collected during the study is being analysed, and will be used to help direct fishing activities in the region, to ensure that the local ‘fishers’ (the birds and seals) are not given a raw deal.
Read Who eats whom around Heard Island [PDF] in the Australian Antarctic Magazine for more details.