Cannibalism assessment of jumbo squid Dosidicus gigas from the Gulf of California

Abstract

In the jumbo squid Dosidicus gigas has been reported a high incidence of cannibalism. The majority of the stomachs reviewed for determining squid diet have been obtained from fishery areas, therefore cannibalism in squids may be overestimated. In this study, a total of 236 Dosidicus gigas stomach contents were analyzed, these were taken from both fishing and non-fishing areas in the Gulf of California and San Carlos (west coast of the Baja California Peninsula) onboard seven cruises carried out between 2005 and 2010. Stomachs were analyzed following the standard methodology and the remains of squid (mantle pieces, suckers, beaks and eye lenses) were separated and weighted and that was called cannibalism weight (% W). Squid mantle length varied from 7 to 86 cm. Bigger sizes were found in fishing areas where cannibalism had major values of cannibalism. The cannibalism weight percentage (%W) and total weight of stomach content (TW) was high in fishing areas, but no significant difference in the frequency of occurrence (%FO) between areas and sex where found. Females presented a higher value of %W than males. The largest sizes had a greater %FO. Results suggest that fishery activities have an important influence in the cannibalism behavior on Dosidicus gigas, therefore this bias should be considered in diet studies when samples are taken from areas where fishing occurs.