Understanding the Elusive Giant Pacific Octopus
See underwater footage of octopus swimming and egg hatching and learn how scientists are tracking and tagging octopus so we can learn more about them.
To learn more about the octopus, read the “Top 12 Weird Facts About Octopus.”
Voice over: They can change shape, texture color and size. They can walk on the bottom of the ocean swim in the water column and mimic other animals. Octopus are about 90 percent muscle and are a source of protein for fish and other mammals. They feed on crabs, bivalves and fish.
They are about 300 specices of octopus in the world but only seven to eight are found in Alaska, the location of a new study designed to help scientists understand the largest species in the world, the giant Pacific octopus.
Liz: The project came about because of fisheries management issues. There are a lot of things about octopus that we don’t know. To set proper catch limits for octopus you want to know two things, how much there are and how fast does it grow.
Voice over: Getting the answers to these questions would require catching the giant Pacific octopus. Traditional trawling methods only catch small octopus so scientists would need to develop another method. They know that local fishermen tend to bring them up in their fishing pots and they also have some behavioral insight that could help them develop an effective catch method.
Liz: One of the things we know about octopus is that they like to have a den, a place to hide when they aren’t actively feeding .So one of the ideas behind the fishing gear is to give them an artifical den that we can attach to a line and haul to the surface.
You would think that when we start to pull the pot back in the octopus would run, but apparently the octopus behavior when it’s disturb is to hold on. They can easily get in and out of these pots, but they don’t. So the gear we’re working with is just a regular fishing longline string, but instead of having hooks on it it has these artifical dens on it.
We’ve tried a lot of things, plastic boxes, plywood boxes, old scrap tires, plastic buckets and plastic water containers and pieces of pipe.
Voice over: Once the octopus is captured, it’s measured, weighed and tagged. However traditional tagging methods weren’t going to work for this eight-legged mollusks, so a new tagging method needed to be developed and tested.
Liz: We can’t use standard tags on octopus because the octopus will grab it and yank it out. The tagging method is basically a brightly colored inert plastic that he injects just under the skin and that tallows us to uniquely ID that octups. Then they let that octopus go, and the fishermen in that area all know to check any octopus they catch to see if they have colored spots in them and when they find one they write it down.
Then Read has the information that that animal that was released on this date and this location was recaptured on that date in that location.
Voice over: This information will tell the scientists if the octopus move around seasonally, their growth rate, and it can be used to determine the number of octopus within an area.
Liz: We’ve gotten very clear results in two areas of the study. The tagging method works very well. The plastics don’t work very well but the plywood boxes work. We’ve learned how big they are, when they start to reach sexual maturity, how many eggs a female produces, we’ve learned a bit about seasonality of reproduction throughout the year.
Real science is about finding out things that nobody knows the answers too. You have to think hard about how to look for it and how to find it. It’s not only do we want to find more about this really neat animal, it’s also directed at what we need to know to manage the species properly.
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