scubaseason

Scalloped hammerhead

Sphyrna lewini

Sighting evidence at Bajo Alcyone, Cocos Island

Scalloped hammerhead

Photo: Peter Geithner · © all rights reserved

Iconic for their laterally-extended cephalofoil — the hammer-shaped head that improves electroreception and manoeuvrability — scalloped hammerheads are pelagic schooling sharks most often encountered at seamounts and offshore pinnacles. Schools of dozens to hundreds form at depth during the day, dispersing at night to hunt. The hammer provides a 360-degree vertical field of vision, making them acutely aware of divers. Critically endangered; fins are among the most traded shark products globally, and populations have collapsed at many historical aggregation sites.

Evidence at this site

58 records within 50 km

Confidence: medium · Schooling behavior strongest at Bajo Alcyone seamount but varies with current.

Seasonality

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How is this calculated?

Sighting evidence is compiled from iNaturalist observation records within a set proximity radius, filtered for quality-grade observations. “Last confirmed” is the date of the most recent research-grade record. Record count covers a rolling 24-month window. Confidence reflects record count, recency, and consistency of seasonal signal.

Also seen at other sites