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TOchre Sea Star
Pisaster ochraceus
The ochre sea star
or purple sea star is a commonly encountered starfish on
rocky beaches from Baja California to Prince William
Sound, Alaska. It has also been found in water up to 100
meters in depth. The ochre sea star is a major predator
of California, edible and bay mussels, and barnacles,
limpets and snails among other species. It comes in a
variety of colours. In the protected waters of Puget
Sound and the Strait of Georgia, the ochre star is
predominantly purple coloured but in other areas, a
bright orange and almost yellow phase is also found. It
is a very rigid sea star to 25 centimeters across. The
ochre star opens its prey using hydrostatic pressure via
hundreds of tiny tube feet to latch on to the shells of
its prey, tugging until they open, and then extruding
its stomach into the opened shells. The ochre star
feeds mostly in summer and moves into deeper water to
estivate in the winter. Gonads begin to grow in January
and spawning occurs from May to July in British
Columbia. A 400 gram sea star can release up to 40
million eggs that then become larvae in the plankton for
up to six months. The same filter feeding mussels that
it will eat as an adult sea star could dine on the
larval sea stars if it were not for an offensive tasting
chemical defence produced by the larvae. Sea stars
mature at about 5 years of age and live for 20 or more
years. In 1988 a parasitic ciliate Orchitophyra
stellarum originating from the Atlantic was found to
be castrating male sea stars in British Columbia.
Further Reading
Kozloff, E. N. 1993. Seashore life of the northern
Pacific Coast. University of Washington Press, Seattle.
Lambert, P. 2000. Sea stars of British Columbia,
southeast Alaska and Puget Sound. UBC Press, Vancouver,
B.C.
(written July 2004)
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