Baltic Herring Identification Guide

Key identification features

• Small, slender-bodied herring, usually well under 20 cm and noticeably smaller than oceanic Atlantic herring
• Bright silvery flanks with a blue-green to steel-blue back
• Single dorsal fin set at mid-body, above or just ahead of the pelvic fin origin
• Deeply forked tail fin
• Smooth belly with only a moderate keel of small scutes, less pronounced than in sprat
• Slim overall build reflecting growth in low-salinity water

Common look-alikes

• Oceanic Atlantic herring: grows noticeably larger and deeper-bodied than the Baltic form, though the two share the same species-level features.
• Sprat: sprat's dorsal fin sits clearly behind the pelvic fin origin and its belly keel reaches farther forward, while Baltic herring's dorsal fin lines up above or just ahead of the pelvic fins.
• Baltic sprat schools: mixed schools require checking fin placement, since Baltic herring and sprat overlap closely in size in this brackish sea.

Where you'll see one

Baltic herring is the local, low-salinity-adapted population of Atlantic herring found throughout the brackish Baltic Sea, from the Danish straits to the Gulf of Bothnia, where reduced salinity limits its growth compared to ocean-dwelling herring.