North Pacific Seastar population decline?
July 25, 2010 by BayKeeper
Filed under Featured, Wild Things
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 sea star 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?
Hi Baykeeper
Re: the Northern Pacific Seastar. I’ve seen plenty of these ghastly pests on McCrae and Rosebud beaches this winter. Maybe as many as in previous years.
I’m sorry but I have to take issue with you saying they are beautiful. I hate the sight of them. Perhaps, as with other pest plant and animal species, once I know the destruction they can cause, their “beauty” completely disappears – for me anyway. I just picture them munching up the native scallop populations, which they apparently do with ease, as the scallop does not recognise the NPS as a predator and just stays in dangers way until too late. And, I hear they first arrived in the Derwent River from Japan in ships arriving to fill up with our Tasmanian native forest woodchips. From there they quickly arrived in PPBay in the 1990s in ballast water. That they have become the most common creature in the Bay in that short time doesn’t help my opinion of them (or the shipping industry) either.
That’s good news those pesty North pacific Seastars are diminishing.
As mentioned, there are promising signs, but there’s still a question mark as to whether they actually are declining. There is a real need for an ongoing systematic survey around the whole Bay.