Earthcare volunteers plucked around 5,000 pest seastars from St Kilda harbour today. The group has conducted similar culls since 2006, recording the numbers collected and their size. The aim is to gain a better understanding of the seastar population’s seasonal behaviour, as well as protect the native species that live in the St Kilda Harbour seagrass beds.
Predator-proof pests?
Four North Pacific seastars (Asterias amurensis) were recorded in Port Phillip Bay in 1997, probably arriving in ship ballast water. Within just 10 years the species was believed to make up around a third of the entire biomass in the Bay. A range of factors contribute to this population explosion. NPS consume almost any animal tissue they can catch. A single NPS can produce 10-20 million eggs a year. As their natural range extends over coasts in northern China, Korea, Japan, and Russia, they have few natural predators in Port Phillip Bay.
In the absence of proven methods to limit the impact of these pests, people power is the best defence available. The Earthcare volunteers are well aware of the enormity of the task. They can’t cover the whole Bay. But at least they are removing the pests from the St Kilda area, to the benefit of the native species. Perhaps other groups around the Bay might take up the fight in their local area too?
