Evasterias is a predacious carnivore.  Its diet consists primarily of bivalves such as the Pacific Blue Mussel (Mytilus trossulus), Butter Clam ( Saxidomus gigantea), Pacific Littleneck (Prothaca staminea), Arctic Hiatella (Hiatella arctica), and the Pacific Falsejingle (Pododesmus cepio).  Barnacles are also a part of Evasterias’s diet and include the Northern Rock Barnacle (Semibalanus balanoides ), Crenate Barnacle (Balanus crenatus), Common Acorn Barnacle (Balanus glandula ) and small Thatched Barnacles (Semibalanus cariosus ).  Evasterias also preys upon the File Dogwinkle (Nucella lima), Sitka Periwinkle (Littorina sitkana), Puppet Margarite (Margarites puppilus) Strigate Limpet (Lottia strigatella), Shield Limpet (Lottia pelta), and Rough Keyhole Limpet (Diodora aspera).

Evasterias catches its prey by using its strong tube feet to pull prey from rocks and pry apart the shells at a rate of 1 mm per minute.  They then evert their cardiac stomach which can fit into spaces as small as .1mm. The stomach can extend a distance equal to half the length of one of the rays.  The stomach releases digestive enzymes that start devouring the flesh of the prey.  The prey eventually dies and is consumed. Evasterias is a top predator and doesn’t therefore have many predators itself.  Once in awhile aSunflower Star (Pycnopodia helianthoides), Glaucous-winged gull (Larus glaucescens) Red King Crab (Paralithodes camtschaticus) or the Sea Otter (Enhydra lutris) have been observed consuming Evasterias.

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