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Researchers to Use Pots, Tags, and Divers in Study of Alaskan Octopus

figure 4, giant Pacific octopus
Figure 4.  The giant Pacific octopus (Enteroctopus dofleini).  Photograph © the Seattle Aquarium.

Research at the AFSC includes not only targeted fish species but also other species that form important parts of the food web and are taken incidentally in U.S. fisheries.

Researchers from the AFSC's Seattle and Kodiak laboratories are preparing to study octopus in the nearshore waters off Kodiak Island in the central Gulf of Alaska and Dutch Harbor in the Bering Sea starting in winter 2010. Funding for the study has been provided by the North Pacific Research Board (NPRB).

The main focus of the study is giant Pacific octopus (Enteroctopus dofleini), which is the largest octopus in the world (Fig. 4) . While seven or eight species of octopus occur in Alaska waters, giant Pacific octopus are the largest and are most likely to be encountered by fishers and divers.

Giant octopus captured in crab or groundfish pots often weigh 50 lbs, and individuals over 100 lbs have been documented. Like all octopus, they have eight arms lined with sucker disks, swim by forcing water 'jets' through a muscular funnel, and can change skin color and patterns to blend in with their surroundings. Their only hard part is a parrot-like beak that allows them to eat mollusks, crabs, and fish.

One important goal of the research is to document the reproductive biology and seasons of octopus in Alaska waters. Researchers need to gather more information about octopus in order to be prepared to provide advice for an ecosystem approach to management of these species, in case a target fishery is developed.

Although there have been some investigations into commercial octopus fishing in the past, there is at present no commercial octopus fishery in U.S. waters off Alaska. Octopus caught incidentally in groundfish fisheries may be sold, but directed fishing for octopus is not permitted.

In state waters (within 3 miles of the coastline), directed octopus fishing is allowed only with a special commissioner's permit from the Alaska Department of Fish and Game (ADF&G). Increasing global markets for octopus have led to increasing interest in retention and sale of octopus over the past few years.

Researchers have posted information with local dive shops and media asking SCUBA divers near Kodiak, Dutch Harbor, and Juneau to watch for octopus. If one is sighted, divers are asked to report the location, time, and date of the sighting, and whether there are egg clusters present in the octopus den. Once octopus dens are located, researchers will revisit the sites monthly from the late summer or fall of 2010 until the early spring of 2011 to determine when the eggs hatch and the octopus larvae leave the den.

AFSC scientist Christina Conrath will be examining reproductive organs of octopus captured in routine bottom trawl surveys, as well as octopus provided by cooperating commercial pot fishermen and fisheries observers, in order to determine when the octopus are ready to mate and lay eggs.

As part of the study, researchers will also be testing and developing 'habitat pot' gear specifically designed for catching octopus. A variety of sizes and materials will be used to build small unbaited pots that serve as artificial dens for octopus; a similar gear is currently used in Japanese octopus fisheries.

The research also includes a pilot tagging study in Dutch Harbor by University of Alaska scientist Reid Brewer. This study will use tiny, bright, flexible tags that will show through the octopusí skin after they are implanted. Both tagging and habitat pot fishing are being developed as techniques to use in future studies to be used for octopus management.

The NPRB grant will provide funds for building habitat pot gear and for chartering commercial fishing vessels for tagging and pot studies. The ADF&G will also participate in the study by providing octopus specimens and helping to build and test habitat pot gear.

By Elizabeth Conners

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