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Monday, August 16, 2010

King Rat: the spotted ratfish will outlive us all

Behold the glory of Puget Sound: the spotted ratfish. 

"I'm the glory of the what now?"
Photo: Wikimedia Commons
I've been planning on doing a blog post on these guys, but the Seattle Times beat me to it with an article that puts the little-known spotted ratfish into the limelight. And rightfully so: ratfish are the dominant vertebrate life form in Puget Sound, and one of the most dominant in the state of Washington: the article mentions that Puget Sound holds an estimated 30 ratfish for every single human in the state!

(An aside: this means big trouble if the ratfish are successful in their attempt to get voting rights, folks. Ratfish are notoriously partisan. They vote as a bloc. So if they do get suffrage, expect to see them ram through the only two items on their agenda: adoption of the 'mollusc standard' for U.S. currency, and an official proclamation that salmon are 'way overrated'. You have been warned, people of Washington).

With a body shaped like a dustbuster, the teeth of a mean rabbit, and eyes that seem to stare past you and into Hades itself, the ratfish isn't immediately attractive. Plus, neither you nor anybody else eats them: they have chicken-gristle cartilaginous skeletons and, according to the Seattle Times article, flesh that is "mushy, with an unpleasant tang" that even seagulls, with their notoriously relaxed palates, find offensive. As if that's not bad enough, they have a poisonous spine and, according the Times again, they are known to bite - with jaws that have the highest leverage ever measured for cartilaginous fish (which, you know, includes sharks). 

So, while by all rights the spotted ratfish should be the state fish of Washington, you'll never even see one on an ad for a fishing charter. Why then should we care about ratfish? 

Well, you should know about them because it's looking like they're doing mighty well for themselves. The Seattle Times article states that in many locations off of northern California, Oregon, and Washington, populations of ratfish doubled during from 1995 to 2006. Why the increase? Nobody's quite sure, but fisheries and changing water conditions are possible culprits. Researchers have documented a widespread shift in fish populations in the U.S. Pacific during the past quarter-century, with populations of long-lived rockfish species declining and fast-growing flatfish and cartilaginous fish (such as ratfish) increasing.

This trend, if it is indeed occurring on the U.S. west coast, bears an unsettling resemblance to the shift that has occurred back east, on the famous Georges Bank fishing grounds. There, decades of intense fishing pressure have been implicated in the widespread ecological shift away from dominance by cod, haddock, flatfish, and other tasty fish to dominance by skates and the truly hated (by fishermen, at least) spiny dogfish. In other words: on Georges Bank, the ecosystem has shifted away from commercial fish towards less-valuable cartilaginous fish, and fisheries are widely implicated as the main driving force of this shift.

Which brings us back to the Pacific and our rabbit-toothed friend, the ratfish. Despite the fact that it's commonly caught and discarded in the B.C. groundfish bottom trawl fishery, there are no stock status reports for the species, and no other publicly-available analysis of ratfish population trends in the Canadian Pacific. It's something that would be interesting to see. While there is no evidence of which I am aware that ratfish populations in Canada's Pacific region are increasing due to the effects of fishing on other species, they do seem to fit the profile of a generalist 'trash' species that expands when other species are removed, and trends in their numbers might indicate broader ecosystem shifts that we would do well to avoid.

So, who knows? Perhaps we are unknowingly clearing the way for ratfish dominance. Or, perhaps it is as the well-known artist Ray Troll has imagined, and the ratfish is simply biding its time for us to go away.

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