During a recent kayaking excursion near Alaska's Berners Bay, resident Bjorn Dihle encountered a pile of pale remains on a local beach. As photos of the find began circulating online, the guesses streamed in. Giant squid? Perhaps a lump of valuable ambergris? Maybe the intestines of some kind of whale? That last suggestion, it turns out, was pretty close ... but no cigar.
Stretched out, the fleshy blob reached almost two meters (about 5ft) in length, and while its strange "tentacles" do bring to mind the boneless form of the giant squid (Architeuthis), what you're actually looking at is the bi-lobed liver of a Pacific sleeper shark (Somniosus pacificus).
Pacific sleeper sharks can be found in waters from Japan to Baja California, and at the southern tip of that vast range, they're known to dive down at least 2,000 metres deep. This preference for extreme habitat means the animals are only rarely seen by humans. Curiously, though, this isn't the case in Alaska.
Dr Dave Ebert, director of the Pacific Shark Research Center at Moss Landing Marine Laboratories, explains that the species is common in Alaskan waters, but there's also another reason behind the frequent local sightings: the animals use this habitat quite differently.
"They occur in shallower water in Alaska than they do, say, off California, where they are usually quite deep," he says. After reviewing Dihle's photos, Ebert feels confident that the "AWOL" organ once belonged to a Pacific sleeper shark.
University of Copenhagen shark scientist Julius Nielsen, who studies the closely related Greenland shark, agrees. "It looks very similar to a Greenland shark liver, so if it is from Alaska, then Pacific sleeper shark sounds like a good guess."
Some online commenters have suggested that the organ may have washed up after the shark was killed by an orca or some other predator, but this scenario doesn't seem very plausible. For starters, killer whales will very happily eat shark livers. "I have no idea how the liver would have ended up in such good condition if [the shark] had been attacked," adds Ebert.
Local fishermen also think it's unlikely that the animal was harvested for food, and the entrails left behind. Some Alaskan peoples do prepare fermented fishes, but this shark usually isn't one of them. "Sometimes people catch them [in Alaska] because they are large, but usually let them go since the meat is pretty bad," says Ebert. "Everyone I know who has tried it had the same perception."
The meat of Pacific sleeper sharks is consumed in Iceland, but only after it's fermented for weeks underground, and then cured into a jerky-like product known as Hákarl. The dish isn't for everyone: the shark flesh is high in ammonia, and produces an odour that's often compared to the smell of household cleaning products. The flavour, on the other hand, is sometimes likened to blue cheese – only much, much stronger and with hints of fish and urine. If cured improperly, meat from the sleeper-shark family is also toxic, and eating it can induce symptoms that mimic extreme drunkenness.
If not food, then what about for catching food? Is it possible that a fisherman had used the animal's meat as bait? It's not likely. The flesh of Pacific sleeper sharks is extremely soft and mushy (a trait shared by many deep-sea animals, including the impressively flabby "sofa shark"). This makes it a poor choice of bait for anyone hoping to catch something more readily edible.
So, just how did this lonesome liver turn up on shore seemingly untouched by humans or marine predators? We might have to look to what the sharks themselves like to eat for an answer.
Unlike their Atlantic kin (who mostly dine on fish, mammals and carrion), Pacific sleeper sharks love to gobble down cephalopods like squid and octopus – the very same invertebrates used as bait by many longline fisheries. Both sleeper and Greenland sharks are master plunderers of longlines, and while a dangling free meal is hard to resist, such raids can be risky business.
If accidentally hooked on the fishing lines, these hefty animals can easily become entangled, or destroy the equipment in the process of trying to get free. In some cases, fishermen are able to release them:
This Pacific sleeper shark was successfully released by Juneau resident Jesse Walker after it became accidentally hooked on his personal-use cod set. The shark swam away in good condition, much to the excitement of everyone on board.
Many snared sharks aren't this lucky, however. And if a hapless animal becomes tightly tangled up and dies, cutting into it is sometimes the only way to free a snarled line. In this scenario, the liver of a cut-up shark may well float ashore with the tide. (Shark livers are rich in oil – it's what makes them so appealing to predators – and the precious liquid they hold is key to maintaining buoyancy.)
Of course, this is just a plausible hunch, and it's certainly odd that a fatty, calorie-rich organ would fail to attract at least a nibble before ending up on land. According to Dihle, just a few seagulls appeared to have pecked at the liver by the time the kayakers arrived on the scene.
If you happen to live in Alaska and have intel on this peculiar sighting, let us know in the comments or drop us a line here. Want to learn more about Pacific sleeper sharks? We've got you covered:
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Top header image: NOAA Photo Library/Flickr
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