Alaska's next fishery?

Researchers study the Giant North Pacific Octopus

Posted: Sunday, August 12, 2007

Charismatic mollusk are not words that are generally used together, but that's exactly how researcher James Browning describes the giant north Pacific octopus. Browning and other Alaska biologists are exploring the potential for a commercial fishery for these fast-growing, short-lived and abundant creatures.

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The giant north Pacific octopus is the largest octopus in the world. The animals grow to 70 or 100 pounds in their three-to-five year life span. It's unusual to find a larger animal, but one caught in British Columbia in 1967 weighed 156 pounds and was almost 23 feet from arm tip to arm tip.

Juneau anglers occasionally catch the octopus when bottom fishing, and crabbers nab them in crab pots. The giant octopus is found in Southeast waters and in coastal waters of Southcentral Alaska west through the Aleutians.

The octopus, Enteroctopus dofleini, inhabits the waters of the continental shelf. Its range extends in an arc from southern California up the west coast, over the north Pacific and then south to Japan. They may be in the intertidal region to depths of 2,000 feet.

Alaska scuba divers are familiar with the animals, as they are often in fairly shallow water.

"They are masters of camouflage," said Jeff Mondragon, a Juneau-based underwater photographer. "You'll see one on sand and it blends perfectly, then it'll swim over to the kelp and completely change color, really fast. It'll even start swaying in the current like it's part of the kelp."

Mondragon said they have excellent vision. They are active day and night, but often den up by day.

James Browning spent decades studying salmon with the commercial fisheries division of the Alaska Department of Fish and Game. He now works with the Alaska Fisheries Development Foundation. He served as a principal investigator in a recent study on the octopus in Lower Cook Inlet and Prince William Sound.

"It's been such a treat to work with octopus," he said. "To be around them, to hold them, tag them and learn about them. They're just tremendous animals to work with."

Browning described a 50-pound octopus with a basketball-size head escaping off the deck of the research vessel. The octopus spied the scupper - a hole two inches tall and 10 inches wide that allows water to drain off the deck - crossed the deck and squeezed out.

"If one arm finds the scupper hole, within one minute it will ooze its whole body through and drop to the water," Browning said.

Giant octopus accounts for roughly 35,000 pounds of annual bycatch taken in state waters during the Lower Cook Inlet cod fishery. The octopi are sold as bait for cod and crab, and in 2006, they netted $26,000 for fishermen.

The University of Alaska Southeast, Alaska Pacific University and Alaska Fisheries Development Foundation cooperated on a study to learn more about octopus in Kachemak Bay, Lower Cook Inlet and Prince William Sound. They hoped to gain stock information about giant octopus to determine if a small boat fishery is feasible. In addition to assessing the resource, researchers wanted to learn more about how to best study octopus.

Researchers included biologists Sherry Tamone and David Tallmon, with student Patrick Berry of the University of Alaska Southeast; and Dr. David Scheel and student Jamie Grund of Alaska Pacific University.

The researchers initially tried to capture animals in June of 2006. After three weeks, soaking 100 traps, they had caught just four animals. Fishermen explained that summer was a poor time to catch octopus, and the researchers decided to return to Lower Cook Inlet in October. They upped the number of traps to 250, and used a combination of custom-made plywood octopus pots (lair pots), shrimp pots, black cod pots and Korean hair crab pots, some baited and others unbaited. Octopus can be caught in unbaited pots because they seek out cavities for shelter.

The difference in timing was profound. "We pulled up to our first string of lair pots and there were 11 octopus in 16 pots," he said. "Another string had 14 out of 18. We went on to tag over 100 animals."

Browning said the researchers returned in December and caught another 100 animals, including three recaptures. The recaptures gave them a sense for the total number of animals in the area. Using telemetry, they were also able to track five animals, which left the area for deeper water after just a few days.

The animals were caught around Yukon Island and Sadie Cove, near where Kachemak Bay joins Lower Cook Inlet. Browning said they generally did not find them in less than 40 fathoms of water (240 feet), and usually between 40 and 80 fathoms.

Browning said he doesn't know why the animals were so scarce in the summer and so abundant in the fall, but it seems they are moving into deeper or shallower waters.

Giant octopus mate in the spring, and the male dies within a couple of months. Females lay 20,000 to 100,000 eggs, tend them throughout incubation (five to seven months), and die shortly after the eggs hatch. Only about one percent of the planktonic larvae survive, but once settled to the sea floor, they grow rapidly and have a significantly higher survival rate.

Browning said although the stock assessment work was done in a limited area, results indicated there were thousands of animals present. "It was very rough, but findings indicate there are lots of octopus, and that's borne out by the high catch by cod fishermen. The resource is there."

Browning said the octopus is well-suited for commercial exploitation. It is fecund, has a high growth rate, is short lived, abundant, and reproductively secretive.

Besides commercial uses, octopuses are valued by artists for their ink, as a traditional food, and by people of all ages who are interested in these remarkable sea creatures for their many intrinsic qualities.

• Riley Woodford is the editor of Alaska Fish and Wildlife News and producer of the "Sounds Wild" radio program. Kim Donohue provides administrative and technical support to the Kachemak Bay Research Reserve in Homer.

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