Predation of newly settled Dungeness crab by juvenile sunflower sea stars

Sunflower sea stars (Pycnopodia helianthoides) are voracious, generalist predators that consume a wide variety of benthic invertebrates across intertidal and subtidal zones (Duggins, 1983; Shivji, 1983; Sloan IUCN, 2020). As one of the largest and fastest sea stars, P. helianthoides are capable of actively pursuing and capturing highly mobile prey, a trait that distinguishes them from many other sea stars. This capacity for active predation mirrors patterns seen in kelp forest consumers, which often derive substantial portions of their diet from both pelagic and benthic sources (Elliott Smith et al., 2021). While numerous studies have documented P. helianthoides trophic interactions and ecological roles (Burt et al., 2018; Galloway et al., 2023; Shivji, 1983), previous work has focused on adult stars, and the diets of juvenile P. helianthoides, and the consumption of pelagic-sourced production in general by this key predator remains unexplored. Here, we define “juvenile” P. helianthoides as stars with a radius of 1% to 10% of the identified prey in these studies. While P. helianthoides is a known generalist predator and scavenger with broad diets, meaningful predation on early life stages of decapod crustaceans has not been previously reported, except for an observation of one megalopa of an unknown crab species found in one P. helianthoides in Central California (Herrlinger, 1983). The finding here that juvenile P. helianthoides can eat ~5 juvenile crabs per day suggests that this predator could exert direct top-down control on crabs soon after their benthic settlement and recruitment, potentially influencing population dynamics of M. magister at local scales. Miles E. Rough: Conceptualization; data curation; formal analysis; investigation; methodology; writing original draft; writing review and editing. Aaron W. E. Galloway: Resources; supervision; formal analysis; writing original draft; writing review and editing. We would like to acknowledge that collections of specimens were conducted on the traditional lands of the Tututni people, part of the Confederated Tribes of Siletz Indians, who have stewarded this region since time immemorial. We thank all the staff at the Oregon Coast Aquarium specifically Tiffany Rudek, Steve Vogel, and Jim Burke. We would also like to thank Sarah Gravem, Ian Kittell, Talia LaForte, Katie Rumsey, Aubrey Taradash, Kersten Schnurle, Caroline Rice, and Faith Townsend for instrumental diving support and field assistance. This work was partially supported by the Oregon Kelp Alliance (NOAA Restoration Center Cooperative Agreement NA25NMFX469C0012) and The Nature Conservancy (P119034) awarded to Aaron W.E. Galloway. The authors declare no conflicts of interest. Data (Rough & Galloway, 2026) are available in Figshare at https://doi.org/10.6084/m9.figshare.31403556.v2. Appendix S1. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.