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Family: Asteriidae

Group: Marine Invertebrate, Species

Scientific NameCommon NameSummary
Evasterias troscheliiMottled starThis common starfish looks somewhat like the even more common Ochre star (Pisaster ochraceus), but its arms taper a little as they near the central disk. Also, Evasterias is less heavily calcified than Pisaster (it is smoother and less rigid), and it lives deeper in the intertidal zone. In the frost-free months, Evasterias troschelli is regularly found several feet above the zero level, but never quite as high as Pisaster. It is also more tolerant of soft substrates than Pisaster, and tends to be more green, brown, or ochre (ironically) than the normally orange, purple, or mixed orange-purple Pisaster.
Orthasterias koehleriRainbow starThis beautiful starfish is only found at very low tides, and is especially common on steep rocky shorelines just south of Sitka. Its dramatic pale spines, striped pink color, skinny arm, and often large size make this species an almost impossible one to mistake.
Pisaster brevispinusGiant pink starThis huge, dramatic starfish is primarily a subtidal species of quiet sandy or muddy bottoms. Although ocasionally found by terrestrial explorers during extreme negative tides, it is more readily observed from small boats in winter when the water is clear. Its incredibly long "reach" with its tube feet and even stomach means that it can stick its tube feet down into the bottom about as far as its arms are long, and then extract the hapless bivalve at the other end. This species is essentially impossible to confuse with any other, thanks to its huge size, short but stiff dorsal spines, and pale pink color.
Pisaster ochraceusOchre starIt is very rigid, heavily calcified, and has broadly triangular arms. This species typically eats Pacific Blue Mussel (Mytilus trossulus) and barnacles (Balanus spp.)
Stylasterias forreriFish-eating StarThis is a subtidal species, which is unlikely to be found by beachcombers. It looks a lot like a cross between Mottled star (Evasterias troscheli), with which it can share color, and Rainbow star (Orthasterias koehleri), which has similar spines. Essentially, a black or brown starfish with prominent white spines is going to be this species. There is another subtidal species in our region which looks like this one, Lethasterias nanimensis, but it has black-tipped spines. In white specimens where the color isn't helpful for distinguishing between this species and Rainbow star (Orthasterias koehleri), look at the pedicellariae (the little "grabber pincers" around the base of the dorsal spines). Those of Orthasterias koehleri are straight like pliers, whereas those of Stylasterias forreri are crooked like mandibles. This is so that this starfish can capture the occasional sculpin or other small fish that may be foolish enough to try and settle onto its back, which is a secondary feeding method for this primarily snail-eating predator.