Copper Rockfish as a den associate: Octopus facilitation of rockfish feeding

Abstract

Rockfish are a predatory fish often found in the rocky terrain and quick currents of the San Juan channel. They are an active area of study for marine scientists, many seeking to know their food sources for commercial and ecological purposes. The populations of rockfish have been on the decline in the Salish Sea. However, since they are a predatory fish, their trophic interactions are much more difficult to study for conservation purposes. One possible interaction to observe is with a well‐known species of octopus, the giant pacific octopus (Enteroctopus dolfleini). The largest of the octopus species, the GPO (giant pacific octopus) is found in the colder habitats of the northern Pacific, living and hunting in rocky areas. They often bring the prey back to their dens or hunt very close to their dens, creating a flurry of prey tissues and juices, leaving behind midden piles full of leftover food for scavengers. When feeding, the GPO will inject paralyzing venom, liquefying the prey as they rip it apart. The octopus pushes out the pile of rubbish and prey remains from the den to keep its area clean. This flurry of feeding activity creates a prime food source for multiple scavengers and potential prey of the rockfish. Larger fish (such as rockfish) often hunt the scavengers eating among the midden piles; preferring benthic crustaceans, and shrimp. Our aim is to observe whether rockfish take advantage of this phenomenon. We hypothesize that rockfish have a direct feeding relationship with GPOs, using the octopus den as the hub of feeding activity.