Interactions of juvenile Octopus vulgaris with scavenging and territorial fishes

Juvenile Octopus vulgaris were often approached or accompanied by fish (<15cm distant), mainly the scavenging slippery dick and the territorial dusky damselfish. Fish were significantly more often near octopuses (56/60 min) when the latter were foraging across the rocky bottom, compared to 26/60 minutes or less when the octopuses were stationary. Octopuses generally ignored fish (83%), although they sometimes changed colour (9%) or made an overt body action (7%), especially when fish attached. The slippery dick caught prey escaping from octopuses and fed on remains of food left in octopus middens. The damselfish attacked foraging octopuses and may have benefited by excluding octopuses who could compete for shelter or eat their eggs. The octopuses excluded from potential foraging areas were made more localizable by predators due to the presence of slippery dicks. These common interactions are another manifestation of Cephalopods’ competition with fish in the marine environment.

Key words:

• Octopus
• behaviour
• fish
• predation
• interaction