Release the Kraken

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

Making headlines today (like the one above) is a new paper by Zoë Doubleday and colleagues documenting an increase the population of cephalopods (octopuses, cuttlefish, and squid) over the past 61 years.  The authors, after assembling a data set of historical catch rates, note that this population increase, rather than being limited to a few localized areas, seems to be occurring globally.

End of analysis.

From then on its speculation.

And the authors speculate that human-caused climate change may be behind the robust cephalopod increase. After all, the authors reason, what else has had a consistent large-scale impact over the past six decades? No analysis relating temperature trends (spatially or temporally) to cephalopod trends, no examination of other patterns of climate change and cephalopod change, just speculation.  And a new global warming meme is born—“Swarms of octopus are taking over the oceans.”

There is an overwhelming tendency to relate global warming to all manner of bad things and a great hesitation to suggest a potential link when the outcome is seemingly beneficial. We refer to this as the global-warming-is-bad-for-good-and-good-for-bad phenomenon. It holds a great majority of the time.

In the case of octopuses, squids, and cuttlefish, the authors are a bit guarded as to their speculation of impact of the increase in cephalopod numbers—will they decimate their prey populations or will they themselves provide more prey to their predators? Apparently we’ll have to wait and see.

No doubt, the outcome will be a complex one as is the case behind the observed population increases. Depletion of fish stocks, a release of competitive pressure, and good old-fashioned natural environmental variability are also suggested as potential factors in the long-term population expansion. But complex situations don’t make for great scare stories. Global-warming-fueled bands of marauding octopuses and giant squid certainly do. 

Reference:

Doubleday, Z. A., et al., 2016. Global proliferation of cephalopods. Current Biology, 26, R387–R407.