The beautiful, but destructive North Pacific Seastar (Asterias amurensis) first arrived in Port Phillip Bay in the 1990s in ship ballast water. As they eat practically anything live or dead that they can climb onto, they thrived in the local conditions where they have few natural predators. In less than 10 years they became the most common animal in the Bay. The fact that that the females are estimated to produce over 20 million eggs could have something to do with it! Naturally, there are concerns that they could out-compete native seastar species.
North Pacific Seastar - it's own worst enemy?
NPS’s tend to spend the summer months in the deeper, central Bay waters, and move nearer to shore in winter. Over the past 5 winters Earthcare volunteers have taken advantage of this seasonal migration to remove thousands of these pests from St Kilda harbour. The most recent cull, conducted today, found hundreds compared to the usual thousands; and young native seastars were noted.
Along with this promising result, several divers have reported not seeing NPS’s in the south of the Bay over the past year. Have they disappeared altogether, or simply eaten themselves out and moved to another area? Baykeeper is keen to hear any reports of NPS’s from around the Bay. Have you seen more or less this winter?
