octopus

Image courtesy of Flickr/DaugaardDK

First a moment to celebrate Octopus Chronicles' 100th post! Little could I have imagined when I started this blog in November 2011 that there would be so much amazing octopus research to cover—and so many wonderful readers. Thank you!

But one thing I have learned in following the field so closely is that we have so many more things to learn about these strange and amazing animals. For one: We have no idea how many octopuses there are out there in the ocean. Not even really an estimate.

In the past several decades we have gotten much better at tracking populations of large fish and marine mammals. Now we can keep better tabs on the numbers of cod or tuna or dolphins as their numbers rise and fall.

But solitary, reclusive octopuses are not so simple to track and count as schooling fish. Add to that that they are nearly impossible to tag, and you have a fisheries management nightmare.

Up through now, the most common way to estimate the size and health of a local octopus population is to see how many local fishermen are catching. But that method has its problems. First, not all species are, of course, of interest—or are accessible—to fisheries. For example, many deep-sea species or smaller shallow-water species aren't worth the trouble to haul in. Second, although their methods might stay relatively stable, fishermen are not out there to get a scientific sample. Perhaps they spend more hours out fishing or change their bait or net size from one season to the next.

So, particularly for the species that are often caught for food, such as the common octopus (Octopus vulgaris), local populations are of keen interest not just to ecologists, but also to fishers, locals and economists. "Although common octopus catches are increasing globally, lack of information on the species biology and fishery has been a major concern in its management," wrote the authors of a recent paper. And when hauls start to turn up empty as they have at various times in Greece, Japan and different costal countries in Africa, governments often intervene to impose fishing restrictions at least until populations appear to have recovered. Even that, however, remains an inexact science.

But we know even less about the details of those species that aren't frequent culinary commodities. It is rare enough for a deep-sea dive to spot an octopus out there in the vast darkness—let alone comprehensively monitor a particular species' population dynamics. And until recently we didn't have much of any way to determine an octopus's age (beyond estimating by weight, which can vary wildly depending on water temperature and diet). So even sampling populations was not an effective way to take stock of changes.

Many forces are at work shaping octopus populations—fishing (we humans have been catching them for thousands of years), predator numbers (including sharks, fish, eels and other octopuses), prey availability (they insist on live meals), ocean temperature (a rise in which is already causing documented octopus species migrations) and water pH (to which octopuses are very sensitive—as are many of their shelled prey).

So although octopuses are primed to be fast adaptors—with short lifespans, generally prolific reproduction and some even being able to edit their own RNA—we have yet to learn just how well they are weathering the storm of human ascendency.

They have, however, been around for at least 300 million years, surviving multiple mass extinction events. So there is a chance they might even outlive us here on Earth.

Or else the octopus robots will.

For more about the past, present and future of the octopus, check out Octopus! The Most Mysterious Creature In the Sea, now also out in paperback!

Illustration courtesy of Ivan Phillipsen