Studies in San Juan Islands, Washington suggest that sea stars may be important predators of sea cucumbers Psolus chitonoides, but not fishes, possibly owing to the presence of aversive chemicals.  Observations in the field of over 100 feeding sea stars show the proportions feeding on Psolus.

Dermasterias imbricata        39%
Pycnopodia helianthoides     19
Solaster stimpsoni                 8
Solaster dawsoni                   8              

Time to digest a Psolus varies from 3d for Dermasterias to 1-2d for the other sea-star species.  Bingham & Braithwaite 1986 J Exper Mar Biol Ecol 98: 311.

The chief sea-star predator of holothuroids on the west coast is Solaster stimpsoni.  One of its prey is the small holothuroid Pseudocnus lubricus, a species often found growing in virtual monoculture in areas of the San Juan Islands, Washington and elsewhere (densities exceeding 400 individuals ^. m^-2).  Although the sea star readily eats Pseudocnus in the field, in laboratory tests 2 other holothuroid species are preferred, Eupentacta quinquesemita and E. pseudoquinquesemita.  Both of these species show escape responses to Solaster, while Pseudocnus does not.  Also, both Eupentacta species are thought to compete for space with Pseudocnus.  The author speculates that S. stimpsoni may contribute to the maintenance of natural monocultures of P. lubricus by preferentially consuming or driving away the Eupentacta species that are competing for space with Pseudocnus.  Engstrom 1988 p. 445 In, Echinoderm biology (Burke et al., eds) AA Balkema, Rotterdam.

NOTE  in Puget Sound, Washington this species is recorded as having a diet of 100% holothurians, including Pseudocnus lubricus (Cucumaria lubrica), and Eupentacta sp., Psolus chitonoides, and Cucumaria miniata. Mauzey et al. 1968 Ecology 49: 603

NOTE  in preference tests, even if the biomass of Pseudocnus is doubled relative to that of Eupentacta, there is still a clear selection for the 2 Eupentacta species

Patchy distribution of sea cucumbers Pachythyone rubra in the Channel Islands, Californiais attributed by a University of California, Santa Barbara researcher to spatially variable, but intense, predation by sunflower stars Pycnopodia helianthoides.  In the western part of the archipelago, cool phytoplankton-rich water provides good conditions for growth and reproduction, but pockets of sea stars take their toll (see map).  In the eastern region of the Channel Islands, the water is warmer and has less phytoplankton.  This leads to less growth and reproduction in Pachythyone, but sunflower stars are absent, so the patches of sea cucumber are more stable over space and time.  Laboratory tests with other potential predators show that only 2 species consume P. rubra: sunflower stars P. helianthoides and spiny lobsters Panulirus interruptus (see graph on Right).  Long-term data from the Channel Islands National Park Kelp Forest Monitoring Program, moreover, show that distributions of the 2 predators do not overlap with patches of P. rubra.  Persistent high percentage cover of P. rubra occurs only at Santa Cruz Island where the 2 predators are in low abundance. Eckert 2007 J Exper Mar Biol Ecol 348: 121.

NOTE  some patches on Santa Rosa Island exceed 4000 individuals ^. m^-2

NOTE  field tests with pelleted dry flesh of Pachythyone show that fishes find something distasteful in them and are deterred from eating