Basking Shark

Cetorhinus maximus

Sighting evidence at Rathlin Island, Ireland

The world's second-largest fish congregates around Rathlin from May through September, drawn by dense zooplankton blooms in the tidal fronts of the North Channel. Individuals reach 10 metres and feed by cruising slowly with their cavernous mouths agape, filtering up to 2,000 tonnes of water per hour. Rathlin is one of the most reliable basking shark encounter sites in the entire British Isles.

Evidence at this site

No confirmed records on file at this site

Basking Shark is listed as a curated species here based on historical reports.

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.