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Government of

Information and public services for the Island of Jersey

L'înformâtion et les sèrvices publyis pouor I'Île dé Jèrri

Protecting and monitoring marine life


There are a few species of dolphin that grace our shores, but it is the bottlenose dolphin that is common to Jersey waters. They are pale to dark grey in colour and reach a size of three to four metres. It's thought that approximately 100 individuals inhabit Jersey waters.

Monitoring dolphins

As part of international obligations, Jersey is required to monitor dolphins found in local waters to ensure it maintains a favourable conservation status.

Marine mammal data collating is done by the marine biology section of The Jersey Biodiversity Centre.

Report a wildlife sighting on The Jersey Biodiversity Centre website


Although not a common species to Jersey waters, harbour porpoises have been sighted here. They generally grow from between 1.4 to 1.9 metres in length and weigh between 61 and 76 kgs. They are dark grey in colour, with speckled sides.

Harbour porpoises feed mainly on small fish, including herring and sprat.

Report a wildlife sighting on The Jersey Biodiversity Centre website

Basking sharks

The basking shark is a highly migratory species and is occasionally sighted in Jersey waters. 

They are one of the largest known sharks, reaching six to eight metres long. There are a number of distinctive features of the basking shark, including a large mouth which contains gill slits to filter feed on zooplankton. They have a pointed snout and are either:

  • dark brown
  • black
  • blue

These sharks are slow moving creatures, and are harmless to humans if left to their own devices. 

Report any sightings of basking sharks with The Jersey Biodiversity Centre.

Report a wildlife sighting on The Jersey Biodiversity Centre website

Code of practice for watching marine mammals

​You should always follow the marine and coastal wildlife watching code:

  • on sighting marine mammals, vessels should gradually slow down to a speed no greater than five knots (or no wake speed) and keep a distance of 100 metres
  • when encountering dolphins whilst moving or if they choose to bow-ride, continue on your intended course, avoiding any unpredictable or erratic movements
  • move away slowly if you notice signs of disturbance, eg hasty dives, changes in breathing patterns, attempts to leave the area or move away from the vessel, erratic changes in speed and direction, lengthy periods underwater, and aggressive behaviours, such as tail slaps and trumpet blows
  • avoid groups of marine mammals with young and never come between a mother and her calf
  • never drive deliberately between groups of marine mammals. Allow them to remain together
  • if safe, switch off all sonar equipment when near dolphins as this can affect their communication and navigation
  • if you discover a solitary dolphin, try to avoid interacting with the animal by maintaining a steady speed in the direction intended. If you are followed into a harbour or marina by a dolphin, contact the Harbour authorities

Jersey marine and coastline wildlife wat​ching code

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