Dynamics of shallow-water populations of Octopus dofleini

Octopus dofleini (Walker) is a common inhabitant of shallow subtidal communities in the Northeast Pacific. The abundances of octopuses at two sites monitored since 1977 have fluctuated greatly during this period. The populations reached high abundances in mid-summer and, during some years, mid-winter. The highest abundances at the two sites did not coincide. There was a constant influx of new octopuses into both study sites, with the greatest immigration occurring in early summer. The octopuses captured spanned a wide range of weights every month, with no clear size classes or seasonal trends in size. The weights of newly-captured octopuses, however, did differ between the sexes and seasons: males weighed more on the average than females, and male weight decreased from winter to fall while female weights did not change O. dofleini appeared to recruit throughout the year; the smallest octopuses occurred between May and November and the greatest number of small octopuses was found in July and August in most years. Females predominated at both study sites throughout the year. However, males predominated among octopuses caught in traps at nearby locations, suggesting that the skewed sex ratios were due to behavioral differences between the sexes.