Sunday, December 7, 2014

The Notorious B.I.G.

"Where does everyone keep getting that number!" I shouted irritably one day while doing some research for the Seattle Aquarium. I was profiling the giant Pacific octopus (Enteroctopus dofleini) and the number that kept coming up was 272Kg/600Lbs. Don't get me wrong, giant Pacific's are well named. They're the largest octopus species in the world, and they can be massive. The largest animal I ever encountered was an octopus named Roland who weighed over 90 pounds and he had an arm span above ten feet.

Giant Pacific octopus also grow incredibly fast. They're short lived, only lasting 3-5 years in the wild, and they go from the size of a grain of rice to broader than a man's height in that time. It's been estimated that they average a gain of 1-2% of their body weight every day. They literally grow exponentially. A well-fed octopus gets bigger today than it got yesterday, and will get bigger tomorrow than it got today.

What had me so flustered about that 600 pound claim is that most giant Pacific octopus never get any bigger than 70 pounds, and the reliable accounts of extremely large animals only weighed around 120 pounds. I found article after article that referenced that size, in both the popular press and the peer-reviewed literature. Six hundred pounds is so far off from what's normally their maximum that I began thinking fish stories might not always be about fish. Many articles even acknowledged that any account above 120ish pounds was probably unreliable.

"I swear it was like two people across!" (Person in this example is defined 
as one elementary aged child) 
Courtesy LAZLO ILYES via Flickr

     Of course it's not not unheard of for a population of animals to shrink over time due to human influence. For example, the dusky grouper (Epinephalus marginatus) from the Mediterranean, is thought to be much smaller than before modern fishing pressure. In ancient Roman murals dusky grouper are portrayed as almost as large as a man, now they rarely get bigger than around 50cm (about 19 inches). Giant Pacific octopus on the other hand haven't really been a targeted catch thanks in part to their chewy texture. It could be that pollution has affected the health of these species, but the reports of truly giant octopus were claimed to be from Alaska where human impact is less significant.

Alright, so where did this number come from? Well lucky for our quest to discover the origins of the "super giant Pacific octopus, TM" , science has a spectacular convention of citation. At the end of every peer reviewed article the authors are expected to cite previous research that informs their experiment and is the basis of their prior knowledge. You can think of it as a built-in BS alarm.

Statistical analypus thinks you should have used an eight tailed test.
Courtesy canopic via Flickr

So I took the opportunity to put on my detective cap and dig around some scholarly research! I have friends I swear, they're humans and everything. Anyway after a little leg work (keyboard work?) I managed to track down the source of the 600 pound octopus in the room. It turns out that in 1975 William High wrote a summary of knowledge about giant Pacific octopus for the National Marine Fisheries Service's annual report. This article was cited by almost every paper I had been looking through, so I suspected it was what I needed. Thankfully the good folks at NOAA keep an online archive of these reports.

In High's summary he discusses how large these animals can get and even he doesn't totally buy the hype at first. He states: "Much larger ones (octopus bigger than 100 pounds) have been reported, but like the Loch Ness Monster, these usually elude the careful photographer or scientist." which is basically the scientific paper equivalent of "cool story bro." But then just a few lines later he goes on to say: "In the late 1950's I interviewed a Canadian commercial diver Jock MacLean... He reported capturing an immense creature weighing 600 pounds and measuring 32 feet from arm tip to top. MacLeans photographs, unfortunately, were of poor quality. Smaller animals, to 400 pounds, were occasionally taken..." Seriously!? Poor quality photos and the testimony of a guy whose job it was to go and get narc'd all the time are all we're going on. You'll have to forgive me if I remain skeptical.

"No you can't be real! The scientific literature doesn't substantiate 
your existence!" -The ship's naturalist
 "Denys de Montfort Poulpe Colossal" by Pierre Denys de Montfort († 1820)
 - Ellis, R. 1994. Monsters of the Sea. Robert Hale Ltd. Licensed under Public domain via Wikimedia Commons  

Sadly it looks like the reports of "super giant Pacific octopus ™" have been exaggerated, even among those who try hardest to avoid hyperbole. Although I can't help but wonder; why is a giant octopus such a universal story? From the legends of the kraken to the creature that supposedly lives under the narrows bridge in Tacoma, Washington; monstrous octopus just capture our imagination. Maybe long ago there were octopus large enough to destroy a ship, or maybe having no frame of reference in the vastness of the ocean led to exaggeration. Either way the real giant Pacific octopus is a huge, magnificent creature that deserves our respect.


Cosgrove, James, & McDaniel, Neil, "Super Suckers: The Giant Pacific Octopus and Other Cephalopods of the Pacfic Coast.", Harbour Publishing, March 2009

High, William, "The Giant Pacific Octopus", Marine Fisheries Review, Vol. 38 No. 9, Sept. 1976
Accessed via:

Guidetti, Paolo, & Fiorenza, Micheli, "Ancient Art Serving Marine Conservation", Frontiers in Ecology and the Enironment, 9: 374-375, DOI 10.1890/11.WB.020

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