Harbour porpoises in the Little Belt

Harbour porpoise (Phocoena phocoena) — one of the world's densest populations; harbour seals. Lillebælt (Middelfart – Fredericia), Naturpark Lillebælt; Fjord&Bælt Kerteminde, Denmark.

Best time: 1 Jun – 31 Aug (June to August). Where: Røjle Klint / Middelfart Søbad, Old Little Belt Bridge (Gamle Lillebæltsbro), Fjord&Bælt, Kerteminde (Denmark). Time of day: Calm early mornings from sunrise for 3 h and the 2 h before sunset from the shore.

• You can go on your own
• Free
• Binoculars helpful
• Sound 3/5

Open it in the interactive calendarSunrise and sunset listening times for the day you pick, and the map.

When is the best time?

Peak: 1 Jun – 31 Aug. June to August (calves, calm water); present all year

Active from 1 Apr to 31 Oct (April to October) in a typical year.

Time of day

Calm early mornings from sunrise for 3 h and the 2 h before sunset from the shore; whale safaris sail by day (check times).

• Morning: sunrise → 3 h after sunrise
• Evening: 2 h before sunset → sunset

What will you hear?

Porpoises are silent to the ear (their clicks are at 130 kHz) — a hydrophone with a wideband recorder gets the click trains; audibly, the sharp puff of a surfacing blow a few metres off the rocks at Røjle Klint, and the Old Little Belt Bridge traffic.

Binoculars?

Binoculars helpful. Porpoises surface a few metres off Røjle Klint; binoculars help pick out fins in the current under the bridge.

Where to go

• Røjle Klint / Middelfart Søbad — Shore watching; porpoises feed in the current under the cliffs; the whale-safari boats leave from Middelfart harbour. Map
• Old Little Belt Bridge (Gamle Lillebæltsbro) — The narrowest point; tidal current concentrates porpoises; rail and road traffic above. Map
• Fjord&Bælt, Kerteminde — Research centre with porpoises in a sea-pen (University of Southern Denmark); hydrophone demonstrations; reference sound. Map

How to go on your own, and what it costs

Shore watching is free: Røjle Klint from the Middelfart Søbad path, or the footpath under the Old Little Belt Bridge at Middelfart (train to Middelfart). Whale-safari boats from Middelfart harbour are paid; Fjord&Bælt in Kerteminde is a paid research centre with sea-pen porpoises for reference.

Cost: Free from the shore; Fjord&Bælt €20 adult (2026); boat safaris (check current prices).

Field-recording notes

To record porpoise clicks you need a hydrophone and a recorder sampling at 384 kHz or more (or a dedicated click detector) — a normal hydrophone chain will give you only the boat and the bridge. The Little Belt is a shipping and leisure channel; the Fredericia refinery and the two bridges are constant. Early mornings in June are calm. Denmark's porpoises are protected (Habitats Directive); whale-safari boats follow a 50 m code. Fjord&Bælt is the place to learn what the clicks look like before going wild.

Sources

• Naturpark Lillebælt – the porpoise
• Fjord&Bælt

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More: all spectacles in Denmark · whales, dolphins and seals · Denmark in June · Denmark in July · Denmark in August