Common octopus settled in human-altered Mediterranean coastal waters: From individual home range to population dynamics

Abstract

A spatially explicit capture-recapture (SCR) model was applied to estimate simultaneously population parameters and individual activity (i.e. home range size) of O. vulgaris, based on experimental mark-recapture data in a human-altered Mediterranean coastal area. Seventy-two octopuses were captured, tagged with subcutaneous PIT-tags and released. Nineteen tagged individuals were recaptured (recapture rate: 26.4%) in the same area over the study period, which spanned over 6 months. Population sizes and densities decreased over the study period, from 337 octopuses (8 ind. ha -1) in September-October to 105 octopuses (2.5 ind. ha -1) in February-March. The highest recruitment probability was estimated to occur at the beginning of the study but it clearly decreased over time, while mortality probability during a fishing period slightly increased. Mean specific growth rate was 0.82 ± 0.11 day -1. Individual home range or activity area ranged from 2.8 ha to 7.3 ha (median home range radius: 121.8 m). Overall, these results suggest that human-altered coastal habitats, which are characterized by abundant shelters, abundant food and absence of predators, can act as settlement and growth areas for juveniles and adults of O. vulgaris. Furthermore, the methodologies applied in this study are recommended as innovative tools to improve management actions of coastal resources.