Tuesday, November 8, 2016

The not so common octopus

Madako, which means 'common octopus,' is a name well known in Japan and, for over a century it referred to the species Octopus vulgaris. The name Octopus vulgaris was first used for the European common octopus, which was long thought to be cosmopolitan with a global distribution.

Molecular studies showed that Octopus vulgaris is actually a mixture of several distinct, though closely related, species. One of these is now recognized as Octopus sinensis, which is found throughout warm seas on the continental shelf of East Asia, including the main islands of Japan which means Madako is not Octopus vulgaris after all.

A new study used morphology and DNA barcoding and the results allow a clear distinction of the two species. The impact of this finding is significant because the growing popularity of octopus as food resource is putting intense pressure on marine resources.

A steady decline in catches of common octopuses around the world is causing concern. Imports of Octopus vulgaris have been masking the decline in Octopus sinensis catches in Japan. And off Europe and Africa, Octopus vulgaris is in trouble, too. The Moroccan octopus fishery collapsed several years ago, while stocks off Mauritania continue to be heavily exploited.

Until recently, the declining numbers caused little concern, as it was assumed that all common octopuses belong to a widely available global species. But now that it's been proven that there are several independent species of common octopus within the Octopus vulgaris group, and that the numbers are limited, researchers are calling for more focus on local fisheries management policies, in order to make sure that each species can be fished sustainably.

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