Mollusks Found Inside Octopus (Mollusca, Cephalopoda) Pots in the State of Ceará, Northeast Brazil

ABSTRACT

The fishery of octopus in the State of Ceará is being carried out in the coast of Fortaleza, Redonda Beach (Icapuí) and Itarema where 2 species can be found, Octopus insularis and O. vulgaris. The objective of this study was to investigate which prey species of mollusks were found inside the pots used in the octopus fishery. Unbaited octopus pots were set in Redonda Beach at 30 meters depth, in Fortaleza at 27 meters depth, and in Itarema at 30 meters depth. The species found inside the octopus pots that were consumed by Octopus vulgaris and O. insularis were mainly gastropods and bivalves. It was found 32 species of mollusks, being 17 of gastropods and 15 of bivalves. Redonda Beach presented the higher number of mollusk species in the octopus pots, with 85% of the total. The most preyed gastropod species was Aliger costatus (35.6%) and the most preyed bivalve species was Anadara notabilis (54.5%). Among the gastropods, 54% had a bore hole, the majority on the spire in the ventral side of the shell. This location is probably due to the presence of the columelar muscle, where it can inject the poison. Only 4.3 % of the bivalves found inside the octopus pots presented bore holes. Empty shells were censured in the field to indicate the magnitude of octopus predation relative to other sources of mortality and the percentage of empty shells with octopus drill holes ranged from 14% to 69%.