Shark on the beach

I usually find something new on my beach walks, but this morning was a big one — a thresher shark. Beached Thresher Shark by CM ParsonsIt was in pretty good shape for being dead and beached. My guess is that it washed ashore with the high tide around sunset last night. It didn’t have obvious wounds and there’s wasn’t much damage from gulls or vultures, yet. But it was fairly bloody (warning for later pictures).

Thresher sharks are beautiful swimmers and easy to identify. This shark group has a very distinctive tail (caudal fin) with the upper lobe about as long as the entire shark. The long caudal fin is for tail-slapping schooling fishes. This stuns or kills the fish, which the shark then eats. In addition to feeding on fishes, threshers also eat squid, of which there are swarms in the bay right now. Beached Thresher Shark2 by CM ParsonsThe beached shark was likely a common thresher (Alopias vulpinus) and about 9 feet (nearly 3 m) long from snout to tail tip. They can grow to 20 feet (6 m).

There’s a fishery for thresher shark meat. Those caught off our coast are considered a “good alternative” on the Monterey Bay Aquarium’s Seafood Watch list. According to NOAA’s FishWatch, not much is known about the current population in the eastern Pacific, but based on their analysis, the species isn’t overexploited. Worldwide, the three species are considered vulnerable on IUCN’s Red List.

Beached Thresher Shark3 by CM ParsonsAs I watched, the tide was rising and it looked as if the body would be washed away by morning’s end. The shark was a great treat for me after so many weeks of tideline crab carapaces and snail shells.

For more about thresher sharks in Monterey Bay, visit the Pelagic Shark Research Foundation. For details on their status worldwide, visit The IUCN Red List of Threatened Species.

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