Sharks
Grey Reef Shark
Carcharhinus amblyrhynchos · Cartilaginous fish — family Carcharhinidae
Grey reef sharks are the metronome of a healthy atoll pass: compact, counter-shaded, white-edged tail flicking as they hold station in ripping current, waiting on the tide. Drift into a Fakarava or Palau channel on the incoming flow and the school materializes ahead of you — first ten, then fifty, then a wall of gray bodies layered from the coral to the surface. They are more assertive than their blacktip and whitetip neighbors and enforce personal space with a famous arched-back display, one of the clearest pieces of body language in the shark world. Their abundance on protected atolls masks steep losses on fished reefs.
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 |
|---|---|---|---|
| PalauPalau | Resident — seen on most dives | 年間を通じて | |
| North & South Malé AtollsMaldives | Resident — seen on most dives | 年間を通じて | |
| Tubbataha ReefsPhilippines | Resident — seen on most dives | Mar–Jun | |
| FakaravaFrench Polynesia | Resident — seen on most dives | Jun–Jul | |
| RangiroaFrench Polynesia | Resident — seen on most dives | 年間を通じて | |
| Coral Sea & Osprey ReefAustralia | Resident — seen on most dives | 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: Current-swept passes, channel mouths, and outer-reef drop-offs; hangs in the flow where baitfish concentrate
分布域: Indo-Pacific — Red Sea and East Africa through the Maldives, Southeast Asia, and Micronesia to the central Pacific atolls
生態・行動: The channel specialist. Greys stack in current like kites on strings, holding formation off atoll passes by the dozen or, at Fakarava, by the hundred. When genuinely cornered the species performs a distinctive agonistic display — back arched, pectorals dropped, exaggerated swimming — which is a clear instruction to back away slowly.
食性: Reef fish, squid, and octopus, mostly hunted at night or in pass currents
サイズ: 目安は 1.5 m; 確認済みの最大記録 1.9 m (total length).
出会ったときの正しいふるまい方
Hook in or hold position at the pass edge rather than drifting into the school's core, keep out of the current line the sharks are working, never chase a displaying animal for a photo, and follow local rules on reef hooks.
保全
Assessed Endangered in 2020; strong site fidelity makes populations easy to fish out and slow to recolonize. Large no-take atolls in French Polynesia, Palau, and the Coral Sea now hold a disproportionate share of the species.
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