Sharks
Pelagic Thresher Shark
Alopias pelagicus · Cartilaginous fish — family Alopiidae
The pelagic thresher looks like a shark designed by a calligrapher — huge liquid eyes, a small mouth, metallic lavender-gray flanks, and a tail that streams behind it in an impossible ribbon. At dawn over Monad Shoal, divers kneel behind rope lines in blue half-light until one rises from the deep and begins its slow carousel around a cleaning station, tail arcing with every turn. It is among diving's most graceful sights and one of its best-managed: local rules on distance and lights have kept the sharks coming for two decades. Elsewhere the species exists mostly as bycatch statistics, which the Endangered listing reflects.
どこで・いつ見られるか
「常駐（Resident）」とは、そのダイビングスポットでのほとんどのダイブで遭遇できることを意味します。「季節限定（Seasonal）」とは、記載された月に確実に見られることを意味します。それ以外の出会いはボーナスであり、計画の前提にはなりません。
| 目的地 | 信頼性 | 月 | メモ |
|---|---|---|---|
| MalapascuaPhilippines | Resident — seen on most dives | 年間を通じて | |
| Brothers, Daedalus & St John'sEgypt | Occasional | 年間を通じて | |
| Marsa Alam & the Deep SouthEgypt | Occasional | 年間を通じて |
ベストな月、一目でわかる
理解を深める
ハビタット: Open ocean and deep seamount flanks; rises to shallow cleaning stations at dawn, one of the few predictable windows into its world
分布域: Indo-Pacific pelagic waters from the Red Sea and East Africa to Mexico; the reliable diver encounters are at Philippine seamounts
生態・行動: A shy, wide-eyed deep-water hunter that visits cleaning stations in the dim early morning, circling patiently while cleaner wrasses work its skin and gills. The tail-slap hunting technique — confirmed on video off Cebu — is unique theater: the shark lunges, brakes, and snaps its caudal fin overhead like a whip.
食性: Small schooling fish and squid, stunned with whip-cracks of the enormous tail before being picked off
サイズ: 目安は 3.0 m; 確認済みの最大記録 3.8 m (total length — the scythe-shaped upper tail lobe accounts for roughly half of it).
出会ったときの正しいふるまい方
Follow the Malapascua protocol that made these dives sustainable: stay behind the viewing lines, no flash where prohibited, minimal movement and noise, and let the shark control its circuit of the cleaning station.
保全
Endangered — slow reproduction (usually two pups) collides with heavy longline and gillnet mortality across the Indo-Pacific. The Philippines' protection of its cleaning stations is a working model of encounter-based conservation.
目撃情報で知られるダイブサイト
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Sink or Swim? with Monét X Change | Monterey Bay Aquarium
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