Porbeagles Continue to Rebound in Canada

It’s been quite some time since the last time I’ve written about porbeagles.  This cold-water shark is encountered relatively often off the coast of New England, where it is both a respectable sportfish (albeit one not fished as often as others because of its tendency to be most abundant in winter) and a pest to longline and gillnet fishermen.  As a member of the Lamnidae family, it’s closely related to great whites and makos, and as a result tends to be overshadowed by its more famous cousins.

The mighty porbeagle. Photo by Andy Murch (elasmodiver.com).

The cool thing about the porbeagle is that it’s one of the few sharks that is a cold-water specialist.  Like the great white and mako, the porbeagle has a system of closely aligned blood vessels called the rete mirabile that transfers heat generated by the swimming motion of its body back into its bloodstream, essentially making the porbeagle a warm-bodied animal.  This allows these sharks to be fast, active predators in an environment where most of the elasmobranchs are fairly sluggish skates and dogfish.

Porbeagles are also the target of a directed fishery in Canadian waters.  Though critically overfished (porbeagles were up for a CITES listing last year), there is some evidence that proactive management of this species has allowed porbeagles to rebound off of Canada.  This article sums up the whole situation nicely (via Underwater Times).  Is it possible that these sharks are capable of rebounding faster than originally expected?  Or could the original amount of decline have been overstated?  Either way it’s good to see this unique species continue to make a comeback.

4 comments

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  3. Jordan · February 5, 2011

    Thanks for the post Chuck! If you read the whole article on Underwater Times, though, you see that there’s no real evidence that the population is ‘rebounding.’ That’s just an anecdote from one fisher who’s seen a lot this year – the actual population assessments show a potentially reversed decline with a recovery trajectory several decades long.

    I agree that it would be great to see porbeagle make a comeback, but it’s far too early to say. More sightings in this case could even just be caused by warming waters.

    • Chuck · February 5, 2011

      Thanks for the comment Jordan. According to the article the porbeagle population is still dramatically below historical levels and with any shark you’re looking at a scale of decades for a full recovery. That said, there have been multiple reports over the last year or so of increased porbeagle presence in the Gulf of Maine (I’ve got a few linked under the “porbeagles” category here). It may be too early to tell if there is a true rebound going on or if the population is just shifting due to climate change or some other factor, but it’s at least been consistent over two years.