Sei whale

Balaenoptera borealis

LENGTH 12–14 m / 39–46 ft

DORSAL FIN Slender and erect; less than 2/3 from front of body

APPEARANCE Blue-grey, dark grey or black back; blowhole and dorsal fin visible simultaneously when surfacing

BEHAVIOUR Narrow, cloud-like blow; rarely exposes tail flukes

Photos by A. Phillips, C. McMillan, J. Towers, J. Ford. Illustrations by A. Denbigh, not to scale.