2015 Assessment of the Octopus Stock Complex in the Gulf of Alaska
February 21, 2015
Octopuses are marine mollusks in the class Cephalopoda. The cephalopods, whose name literally means head foot, have their appendages attached to the head and include octopuses, squids, and nautiluses. The octopuses (order Octopoda) have only eight appendages or arms and unlike other cephalopods, the octopus lack shells, pens, and tentacles. There are two groups of Octopoda, the cirrate and the incirrate. The cirrate have cirri (cilia-like strands on the suckers) and paddle-shaped fins suitable for swimming in their deep oceanic pelagic and epibenthic habitats (Boyle and Rodhouse 2005) and are much less common than the incirrate which contain the more traditional forms of octopus. Octopuses are found in every ocean in the world and range in size from less than 20 cm (total length) to over 3 m (total length); the latter is a record held by Enteroctopus dofleini (Wülker, 1910). Enteroctopus dofleini is one of at least seven species of octopus (Table 1) found in the GOA. Members of these seven species represent six genera and can be found in depths from less than 10 m to greater than 1500 m. All but one, Japetella diaphana, are benthic octopuses. The state of knowledge of octopuses in the GOA, including the true species composition, is very limited.
In the GOA, octopuses are found from subtidal waters to deep areas near the outer slope (Figure1). The highest species diversity is along the shelf break region of the GOA, although there is a high abundance of octopuses on the shelf. While octopuses are observed throughout the GOA, they are more commonly observed in the Central and Western GOA (areas 610-630) than in the Eastern GOA. The greatest numbers of observations are clustered around the Shumagin Islands and Kodiak Island. These observations are influenced by the distribution of fishing effort and may not reflect true spatial patterns. Octopuses were caught at all depths ranging from shallow inshore areas (mostly pot catches) to trawl and longline catches on the continental slope at depths to nearly 1000 meters. The majority of octopus caught with pots in the GOA came from 70-110 meters; catches from longline vessels tended to be in deeper waters of 200-400 fathoms (360-730 meters). AFSC survey data also demonstrate the presence of octopus throughout the GOA and also indicate highest biomass in areas 610 and 630. Octopuses are also common in the eastern Bering Sea and throughout the Aleutian Island chain.