Winter feeding by asteroids on a subtidal sandbed in British Columbia

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Abstract
The winter feeding of the asteroids Mediaster aequalis, Luidia foliolata, Pisaster brevispinus and Pycnopodia helianthoides on a subtidal sandbed in British Columbia is reported. Bivalve predation and experiments with the latter three species examining size-related predation, sand as a prey refuge and prey escape behavior are reported using the cockle Clinocardium nuttallii. M. aequalis is a small species with a very broad diet and mainly a microphagous feeder which may graze recently settled bivalve larvae. L. foliolata is a burrowing species which specializes in swallowing small infaunal bivalves whose size usually cannot exceed its disc (mouth) diameter of 40 mm. P. brevispinus is large and grazes barnacles on hard substrates, and on sand specializes in excavation of larger bivalves such as the geoduck clam Panope abrupta and the jacknife clam Solen sicarius. P. helianthoides is a large, highly opportunistic predator which grazes epifauna on hard substrates, excavates larger bivalves from sand, and, after encounter, pursues exposed prey such as large cockles. Thus, the different asteroid feeding modes vary in effect on different sizes and species of bivalves. All bivalves to 40 cm depth in the sand are potentially available prey for one or more of the asteroid species.