Dolphins, porpoises and basking sharks
Dolphins
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 3 - 4 metres. Dolphins breathe at the surface through their blow holes and swim in pods of 2 - 25 individuals. The bottlenose dolphin hunts for mackerel and cuttlefish using echo-location. It is 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 Société Jersiaise. If you would like to tell us about a dolphin sighting please use the form below.
Report a marine life sighting on Société Jersiaise website
Porpoises
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. Please report any sightings of porpoises.
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 6 - 8 metres long. There are a number of distinctive features of the basking shark, including its very large mouth which contains gill slits to filter feed on zooplankton. They have a pointed snout and are either dark brown, black or blue in colour. These sharks are slow moving creatures, which are harmless to humans if left to their own devices. Please report any sightings of basking sharks.
Code of practice for watching marine mammals
- on sighting marine mammals, vessels should gradually slow down to a speed no greater than 5 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, such as: 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
Download Jersey marine and coastline wildlife watching code (size 591kb)