Potential limiting factors to the growth of Octopus vulgaris

Introduction and Aims Octopus vulgaris is a highly valuable food resource and good candidate for marine aquaculture. Over the past years, more than a hundred of published papers have been devoted to increase the growth performance of captive octopuses and overcome the problems associated with the adaptation of these animals to farming conditions. Despite this effort, the farming of O. vulgaris is still far from being a large-scale, economically profitable activity due to high costs, heavy losses in terms of mortality and inadequate growth. Malabsorption syndrome due to parasite load, and competition for food due to elevated territoriality of animals in the cages have been considered as the main limiting factors for a successful ongrowing of O. vulgaris. Approaches and Results In order to explore possible factors limiting growth of animals, historical long-term data on the growth of O. vulgaris in standardized uniform maintenance conditions have been correlated with confounding factors such as season, temperature, genetic factors, parasitic infections. In addition, effect of habituation to a social context have been applied to increase the willingness of octopuses to actively feeding on administered prey items. We show that parasitic load is not directly correlated with decreased growth, but to metabolic factors linked to genetic differences and possibly to changes of temperature in the holding conditions. Habituation to a social condition, allow subordinate individuals to re-equilibrate the feeding hierarchy and reduce the competition for food, thus also increasing the chances for a more uniform growth of animals held in the same cage. Standardized Fulton Condition Index confirm the view that inter-individual differences in animals\u2019 growth are largely linked to metabolic and genetic factors Conclusions Non invasive strategies to facilitate selection of individuals for the rearing are suggested, thus to maximize animals\u2019 growth. In addition, improvement of aquaculture success is presented through the application of a behavioral-welfare approach