Abstract
This study highlights for the first time individual differences in ethology and vulnerability of Octopus vulgaris (i.e. body postures, movements and skin displays) facing passive baited traps. Common octopus exposed to a baited trap during three consecutive first-capture tests exhibited diverse behavioural and body pattern sequences resembling when the octopus searches for and hunts its wild prey. Overall, they first visually recognized new objects or potential preys and rapidly moved out of the den, exploring, grabbing and approaching the trap with the arms (chemotactile exploration), and capturing the bait with the arms and feeding on top over long periods inside the trap. Simultaneously, O. vulgaris displayed diverse skin textural and chromatic signs, the regular pattern being the most frequent and long-lasting, followed by broad mottle, passing cloud and dark patterns. All individuals (n=8) caught the bait at least once, although only five octopuses (62.5%) entered the trap in all three tests. In addition, high variability among individuals was observed regarding behaviour and body patterns during the first-capture tests, which might evidence different individual temperaments or life-history traits. Differences in behavioural responses at individual level might have population consequences due to fisheries-induced selection, although there is a high necessity to assess how behavioural traits might play an important role in life-history traits of this species harvested by small-scale trap fisheries.
Highlights
The common octopus (Octopus vulgaris Cuvier, 1797) is a cephalopod species of high ecological and economic interest worldwide
Summary: This study highlights for the first time individual differences in ethology and vulnerability of Octopus vulgaris facing passive baited traps
Common octopus exposed to a baited trap during three consecutive first-capture tests exhibited diverse behavioural and body pattern sequences resembling when the octopus searches for and hunts its wild prey
Summary
The common octopus (Octopus vulgaris Cuvier, 1797) is a cephalopod species of high ecological and economic interest worldwide. It is mainly distributed throughout the Mediterranean Sea and in central-eastern Atlantic waters, though morphological and genetic differences have been described among populations in its distribution range (Jereb et al 2015, De Luca et al 2016, Amor et al 2017). Landings from coastal artisanal fisheries have high local economic and social importance in Southern Europe, but overall common octopus landings have declined since the mid-1980s (Pierce et al 2010). Direct underwater observations by visual censuses have been successfully applied to directly assess individual activity and specific ecological and behavioural traits of O. vulgaris populations in shallow coastal waters More detailed behavioural studies are difficult to perform in natural conditions, so experimental studies in captivity are sometimes a good tool for determining where to make the first steps and fill the gaps in existing knowledge
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