Diet and Feeding Behavior of the Deep-Water Sea Star Rathbunaster Californicus (Fisher) in the Monterey Submarine Canyon

Diet was determined for 98 specimens of Rathbunaster californicus (Fisher), a deep-water sea star, collected with a Remotely Operated Vehicle (ROV) between 380 and 650 m depth within the Monterey Submarine Canyon, California. Gut content analysis revealed at least seven phyla among the prey items, with crustaceans (especially benthic-dwelling caprellid amphipods) predominating. The presence of large decapod shrimps, hyperiid amphipods, other midwater crustaceans, siphonophore parts, and a tomopterid polychaete in stomach contents indicated that R. californicus can catch highly mobile, midwater animals swimming close to the substratum. Such active predation was seen directly via the ROV's video system, which showed R. californicus catching euphausids, sergestids, and a myctophid fish. In the laboratory, the sea stars engulfed dead food items such as squid and smelt and used their pedicellariae to catch mobile prey such as brine shrimp. These data show that R. californicus in Monterey Bay is an opportunistic predator and scavenger and is one of few sea stars reported to be capable of catching midwater prey.