Biodiversity: Marine Mammals

The southern North Sea is home to several species of marine mammal, such as the harbour porpoise (a small species of dolphin), the common seal and the grey seal. Groups of white beaked dolphins are also frequently observed in the area. The bottle nose dolphin, the type found in dolphinariums, is all but extinct in the North Sea and is only rarely seen. Any species of marine mammal that would normally be found in the north eastern Atlantic is quite likely to stray towards our coastline. For example, recently there have been the strandings of a humpback whale, a common rorqual and several sperm whales. However, northern fur seals, such as the bearded seal, harp seal, ringed seal, hooded seal and walrus are very rarely seen in our coastal waters.

Common seal

In recent years sightings of seals and porpoises have become more common in our waters. In our neighbouring countries seal populations have increased, and a southward population shift is the most likely explanation for the general resurgence of the porpoise in the southern North Sea. The reasons for this are still unclear.


Marine mammals are legally protected: this means that they mustn't be deliberately disturbed, captured or killed, and that measures have been put in place to prevent people inadvertedly disturbing or killing them.

The OD Natural Environment coordinates the study of any marine mammals that are washed ashore. Of those marine animals that do end up on the beach, a number are selected for further study, such as autopsy. 

The information gained through autopsy tells us a great deal about the animals themselves, the general health of the population and the problems they face. Such problems include pollution by oil, pesticides, heavy metals and PCBs (polychlorinated biphenyl), overfishing and getting caught in fishing nets.


The collections held at our museum and other scientific institutes contain a selection of skulls and skeletons for study and teaching. Sightings and strandings of marine mammals are recorded in a database which is available online.



Besides marine mammals and seabirds the legislation protects sea turtles and a number of marine fish, such as the sturgeon, the sea lamprey and the twait shad (Royal Decree of 21 December 2001). Along with marine mammals and sturgeon there are several other species which fishermen have a duty to report if they unintentionally catch them. Any instances of seabirds washed ashore are routinely investigated by INBO.


What should I do if I observe a protected marine animal, find one beached or inadvertently catch one in my nets?

If you see the carcass of a marine mammal or a turtle, or a live dolphin or turtle, the best thing to do is to inform MUMM as quickly as possible:

  • 059 70 01 31 (office hours)
  • Police or Fire brigade (outside office hours)


Observations of live marine mammals can be reported to MUMM:

Fishermen sometimes report the matter if birds or marine mammals have become caught up in their nets. These reports are treated with complete discretion where necessary.

If you find a live seal in distress (ill, weak, wounded), you can report this directly to Sea Life Blankenberge (050 42 43 00, 24/7). They are responsible for the rehabilitation of these seals.

During the summer months, young and weak common seals may be washed ashore along the Belgian coast. Without human intervention, these animals would not survive. A small seal in distress looks thin and lifeless. It can be approached relatively easily. In a situation like this, follow these rules:

  1. Do not cause any unnecessary stress. Allow the animal to come ashore and make sure members of the public keep their distance.
  2. Do not touch the animal. It may bite and transmit germs to humans.
  3. Inform Sea Life Blankenberge.

A seal on the beach does not necessarily need assistance. Healthy animals look for a place to rest in the daytime. Common seals are born on sand banks or beaches. If you see a clearly healthy seal, the first thing is to make sure that you do not disturb the animal. Observe it from a distance.

Info brochure 2013 (in Dutch): What should I do if I observe a protected marine animal, find one beached or inadvertently catch one in my nets?

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