Bird vomit to help gauge sardine abundance
Greater crested tern (Sterna Bergii), D'Estrees Bay, Kangaroo Island
Fisheries researcher Dr Lachlan McLeay has developed an approach to gauging sardine abundance through looking at the diet, health and population dynamics of crested terns – by studying their vomit.
“Crested terns are a small fish-eating seabird living in marine waters of South Australia,” explained Dr McLeay, who works at the South Australian Research and Development Institute (SARDI).
“My data shows that information collected from crested terns can be used to monitor marine ecosystem health, such as the abundance of sardines in the ocean.”
The number of sardines in Australian waters is currently estimated by weighing up the active biomass – based on the production of eggs by female adult fish – against fisheries catch data. However, this technique does not take into account the ecological interactions sardines have with many species, including terns.
To develop a new approach to measuring fish abundance, Dr McLeay focussed on two major sardine mortality events of the 1990s, when approximately 70% of adult sardines in South Australian waters died due to a virus. He found that terns rely on sardines in their diet (that’s where the vomit comes in) and that tern chick survival is related directly to sardine abundance.
Using GPS tracking devices, he also found that adult terns have a restricted foraging range, making them particularly vulnerable to losses in local sardine numbers.
“My data shows that we can use terns to help us inform conservation strategies and manage marine resources better,” Dr McLeay says.
He hopes that terns will provide a tool for enhancing management practices for Australia’s largest fishery, the South Australian Sardine Fishery.