How do we identify octopuses seen from the submersible or released live after weighing and measuring?
We rely on field id characteristics as detailed in Roland Anderson's "Field key to live common west coast octopuses" (unpublished) to identify octopuses in the field. Additional field characteristics were described by Ian Gleadall.
Only three species of octopus are supposed to occur in our study area (Prince William Sound and Cook Inlet, Alaska) - the Giant Octopus (Enteroctopus dofleini, previously Octopus dofleini), the Red Octopus (Octopus rubescens) and Benthoctopus leioderma (Enteroctopus and Benthoctopus following Hochberg 1998). Of these, only rubescens and dofleini are supposed to occur in shallow water. As a bonus, leioderma doesn't look anything like the other two, so even if we stumbled across one, we would know something was different.
Note that these characteristics are suitable to seperate the Giant Octopus from the Red Octopus (Octopus rubescens), as these are the only two common species likely to be confused in Gulf of Alaska waters. However, in the southern portions of its eastern Pacific range (i.e. Californian waters), the Giant Octopus may also co-occur with Octopus micropyrsus, O. bimaculoides, O. bimaculatus, and O. californicus. The information here has not been checked for ability to discriminate among these species nor among species that co-occur with the Giant Octopus in western Pacific waters.
Also note that on this page, the common name Red Octopus refers to Octopus rubescens in the eastern north Pacific, and not to Enteroctopus megalocyathus in the eastern south Pacific & south Atlantic (i.e. in Chilean & Argentinan waters). Enteroctopus megalocyathus is also refered to as "pulpo colorado" or the red octopus.
Note that in live 1-10 kg Giant Octopus, all these characters are only intermittantly visible. See the Anatomy page for a photo showing paddle-like papillae, the central white spot and white streak, and bars down the arms. Finally, while crawling around out of water, dofleini is bright red and rubescens is muddy brown.
