Seastar survival strategy

Curiously, the Magnificent Biscuit Seastar Tosia magnifica is reported as relatively common in waters up to 5m in Victoria and Tassie, but is only found in deep water (to 200m) in South Australia. Just one more of those marine mysteries! But it may well be that this ability to use a range of depths will be the key to the species survival in the face of competition for food from the introduced pest North Pacific Seastar Asterias amurensis.

As Susie Inglis’ pic from Hobsons Bay shows, the Magnificent Biscuit Seastar is a dainty little critter. At around 45mm wide they’d be no match in an arm wrestle with the much larger and more abundant North Pacific Seastar. Lets hope their choice of depth is SA may give them safe haven from these unwelcome pests.

NP Seastars came to Port Phillip Bay in ship ballast water in the mid 1990′s and rapidly became the most abundant creature in the Bay. The fact that they’ll eat practically anything (living or dead) that they find on the seabed is a big part of their success. Whereas Magnificant Biscuit Seastars, believed to graze on living plants, aren’t so easily pleased.