Habitat, distribution, and abundance of the commercial octopus (octopus insularis) in a tropical oceanic island, Brazil: Information for management of an artisanal fishery inside a marine protected area

Abstract

The spatial distribution, abundance and habitat of a population of a shallow-water octopus, Octopus insularis, subject to some fishery pressure,was studied in the Fernando de Noronha Archipelago, a marine protected area off northeastern Brazil. Three techniqueswere used: visual censuses in fixed quadrants and in roving-diver and catch per unit of effort (CPUE) of the commercial fishery.We had two hypotheses, that the species had a nonrandom distribution, related to substrate and body size, and that relative abundance outside the national parkwould be lower than within, possibly due to fishery pressure.We found a patchy distribution over all, with octopuses almost confined to substrates with a large proportion of hard surfaces. Therewere seasonal and depth effects on distribution of the very small octopuses found mainly in shallow water (intertidal to 5m depth) during the dry season. Abundance was similar inside and outside of the national park, which suggests that the octopus fishery is not a threat to the abundance of O. insularis at this present level.