Ochre Sea Star
Pisaster ochraceus
Ochre stars come in a variety of colors and have many small spines on their bodies that form a net-like shape on their central disc. They are a keystone species, keeping coastal tidepools in balance by controlling mussel populations. This helps the entire tidepool stay diverse and healthy.
These sea stars have been heavily impacted by sea star wasting disease, which causes tissue decay and eventual death of the sea star.
Originally published: March 14, 2025
Last updated: May 04, 2026
Credit: iStock.com | Ken Canning
SPECIES IN DETAIL
Ochre Sea Star
Pisaster ochraceus
CONSERVATION STATUS: Not evaluated
CLIMATE CHANGE:
Geographic Distribution
These sea stars are found between Alaska and Baja California.
Habitat
Ochre stars live in intertidal zones and rocky shores, generally occupying the same habitats as mussels, which they eat in great abundance. After their larval stage, juvenile ochre stars tend to stick to crevices and hide under rocks.
Physical Characteristics
Ochre sea stars have five stout arms fanning out from their central disk. Their upper sides have many ossicles or small spines that feel rocky and hard to the touch. The ossicles, part of the endoskeleton that provides structure and protection to the sea stars, form a netlike or pentagonal pattern on their central disks. These sea stars have a wide range of colors, including purple, orange, yellow, reddish, and brown.
Size
Ochre stars can grow as big as 35 centimeters (14 inches) across.
Diet
In their larval stages, these sea stars are filter feeders that consume mostly plankton. As adults, ochre stars feed on mussels, which is crucial to keeping that population in check. Adult ochre stars also eat snails, barnacles, limpets, and small crustaceans.
If prey is too big to eat whole (like mussels), the ochre stars can pry the shells open with their tube feet. They evert their stomach (turning it inside out so their stomach is outside their body) to begin the digestion process.
Reproduction
Ochre stars reproduce by broadcast spawning. Females release eggs while males release sperm into the water column. Upon fusing they then go through several larval stages and eventually settle and grow into adult sea stars.
Behavior
Ochre stars tend to stick to areas that offer them refuge from environmental stressors and predation risk. They seem to prefer shaded areas over sun-exposed ones, even when they’re not in harm’s way from thermal stress.
Adaptation
Ochre stars fluctuate their weight cyclically depending on food availability. When mussels are plentiful, ochre stars tend to grow much larger.
Sea stars use their sticky tube feet to move around their environment as well as hold onto their prey.
When an arm is lost, they can regrow one slowly, taking several months to up to a year to complete the process.
Longevity
Ochre stars can live up to around 30 years.
Conservation
The population trends of ochre stars has not been assessed by the IUCN. However, their population has been heavily impacted by sea star wasting disease with a 75% to 100% mortality rate at 80% of sites studied. Sea star wasting disease causes tissue decay and often death in affected sea stars. Researchers are also concerned with the potential future impacts of the loss of ochre star genetic diversity caused by this loss of life.
Ochre stars face natural predation from sea otters and seagulls. They are also collected by humans for the seashell trade.
Special Notes
To eat tightly-closed mussels, ochre stars can evert (turn inside out) a small portion of their stomach or even just some digestive juices into very narrow openings in mussels. Ochre stars can use their very strong tube feet to pry open the mussels the rest of the way, ensuring that they get their meals.
SPECIES IN DETAIL | Print full entry
Ochre Sea Star
Pisaster ochraceus
CONSERVATION STATUS: Not evaluated
CLIMATE CHANGE:
These sea stars are found between Alaska and Baja California.
Ochre stars live in intertidal zones and rocky shores, generally occupying the same habitats as mussels, which they eat in great abundance. After their larval stage, juvenile ochre stars tend to stick to crevices and hide under rocks.
Ochre sea stars have five stout arms fanning out from their central disk. Their upper sides have many ossicles or small spines that feel rocky and hard to the touch. The ossicles, part of the endoskeleton that provides structure and protection to the sea stars, form a netlike or pentagonal pattern on their central disks. These sea stars have a wide range of colors, including purple, orange, yellow, reddish, and brown.
Ochre stars can grow as big as 35 centimeters (14 inches) across.
In their larval stages, these sea stars are filter feeders that consume mostly plankton. As adults, ochre stars feed on mussels, which is crucial to keeping that population in check. Adult ochre stars also eat snails, barnacles, limpets, and small crustaceans.
If prey is too big to eat whole (like mussels), the ochre stars can pry the shells open with their tube feet. They evert their stomach (turning it inside out so their stomach is outside their body) to begin the digestion process.
Ochre stars reproduce by broadcast spawning. Females release eggs while males release sperm into the water column. Upon fusing they then go through several larval stages and eventually settle and grow into adult sea stars.
Ochre stars tend to stick to areas that offer them refuge from environmental stressors and predation risk. They seem to prefer shaded areas over sun-exposed ones, even when they’re not in harm’s way from thermal stress.
Ochre stars fluctuate their weight cyclically depending on food availability. When mussels are plentiful, ochre stars tend to grow much larger.
Sea stars use their sticky tube feet to move around their environment as well as hold onto their prey.
When an arm is lost, they can regrow one slowly, taking several months to up to a year to complete the process.
Ochre stars can live up to around 30 years.
The population trends of ochre stars has not been assessed by the IUCN. However, their population has been heavily impacted by sea star wasting disease with a 75% to 100% mortality rate at 80% of sites studied. Sea star wasting disease causes tissue decay and often death in affected sea stars. Researchers are also concerned with the potential future impacts of the loss of ochre star genetic diversity caused by this loss of life.
Ochre stars face natural predation from sea otters and seagulls. They are also collected by humans for the seashell trade.
To eat tightly-closed mussels, ochre stars can evert (turn inside out) a small portion of their stomach or even just some digestive juices into very narrow openings in mussels. Ochre stars can use their very strong tube feet to pry open the mussels the rest of the way, ensuring that they get their meals.