Yearly stranding reports

As part of the implementation of the Royal Decree on marine species protection in the Belgian national waters, the institute produces annual reports on observations and strandings of marine mammals in Belgium. These reports are available in Dutch and French on this web page (previous reports only in Dutch). Printed copies can be requested at

Report of 2023

In 2023, 26 harbour porpoises washed up in Belgium: the lowest number in the past 20 years. Most of these animals were in an advanced state of decomposition. The reason for the declining number remains subject to speculation.

A comprehensive analysis of the data collected during aerial surveys (2009-2022) indicates that porpoises mainly occured in high densities in our waters in spring. They preferred the northern and western parts, and seemed to avoid shipping routes.

48 dead seals washed ashore in 2023. Ten of them are believed to have died in fishing nets. Sealife took seven Grey and 17 Harbour seals into care. Almost half of the animals didn't make it.

In the port of Antwerp, a dead fin whale was brought in on the bow of a ship. The autopsy confirmed that the animal had died as a result of the collision.

Some rare dolphins for our country washed up in 2023: a Common dolphin and two very decomposed Common or Striped dolphins.

The most notable cetacean was a Orca: at first the animal moved slowly along the coast, eventually ending up stranded. It died very shortly after the stranding. So far, it could not be determined which population the animal came from. It has been since the mid-19th century that strandings of Orcas were recorded in our country. We have tried to unravel the information about those long-ago strandings. We also pay tribute to the man to whom we owe the fact that we can still admire the remains of these animals, now more than 175 years old.

Some sea turtles also washed ashore in 2023. A dead Leatherback Turtle died from traumatic causes, while a Loggerhead Turtle that stranded alive was the first confirmed stranding of this species in Belgium.

Report of 2022

Which dead or dying marine mammals washed up on our beaches? Which causes of death could be identified? What are the trends of marine mammals in Belgium? How many seals did Sealife take in? Which rare species were observed? These are the questions to which one can once again find the answers in the marine mammal report, this time focusing on the results from 2022.

In 2022, 45 Harbour porpoises washed up on our beaches, the lowest number since 2004. Four of these stranded alive, but all died on the beach or during attempts to rescue them. One of the animals was pregnant. Aerial surveys over the Belgian part of the North Sea in March and October resulted in estimates of over 11,000 and over 2,000 Harbour porpoises. The March number was the third highest number documented since surveys began in 2009. A Harbour seal was probably born on the right bank of the IJzer estuary at Nieuwpoort: a first for our country as no records of seal births in Belgium in the 20th or 21st century are known.

With 54 seals washed ashore dead (18 Grey, 10 Common and 26 that could not be identified to species), 2022 was good for the second highest number of dead seals in the time series. Only 2021, when 101 dead seals washed ashore, had more. A large proportion of these appeared to be victims of fishing with passive gear. 12 Grey seals and three Harbour seals ended up in the shelter of Sealife Blankenberge.

Two Humpback whales were seen in Belgian waters and there were two sightings of groups of White-beaked Dolphins. The solitary Bottlenose dolphin, social towards humans, was still present in the border area with France. Also a dead Bottlenose dolphin washed ashore, as did a living Sowerby’s beaked whale. Also a living non-identified beaked whale was seen, while a dead Fin whale drifted along the Belgian coast before finally washing up in the Netherlands.

Boxed sections take a closer look at 30 years of ASCOBANS (Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas), a project to avoid collisions of ships with whales, the role of the North Seal Team in protecting seals and measures related to the avian flu virus, which also affected marine mammals in a number of places around the world in 2022.

Report of 2021

Also for 2021, the Royal Belgian Institute of Natural Sciences coordinated a report 'Strandings and sightings of marine mammals in Belgium in 2021', that summarises the results of monitoring and scientific research on marine mammals in Belgium.

In 2021, only harbour porpoises and seals stranded in Belgium. However, this involved a lot of work, as the number of dead seals doubled to more than 100, compared to an almost constant number in the 2018-2020 period (44 on average). Determining the cause of death proved to be a real challenge. As many of the dead seals appeared to be 'decapitated', much commotion and speculation arose. In the end it turned out that many of the animals concerned had died in fishing nets.

With 74 stranded Harbour porpoises, 2021 was a rather moderate year. The cause of death could be determined for 30 porpoises: 15 fell prey to Grey seals (which is a remarkable number), 12 died of infectious diseases or starvation and 'only' 3 drowned in fishing nets.

Four live Harbour porpoises also stranded, all of which unfortunately died soon after stranding. Aerial surveys showed almost 3,000 Harbour porpoises in our waters during June and September.

Sealife Blankenberge took in eight Grey and 10 Common seals in 2021. Bite wounds (of unknown origin), injuries caused by the nylon rope of a fishing net, and other waste at sea (rubber ring), were at the basis of the need for rehabilitation. Six Grey seals and seven Harbour seals could be released. In contrast to the past, young Grey seals are now more often left lying on the beach: they become more numerous and they do not need our help most of the time.

The annual report also devotes attention to the death of Grey seal Oscar. This very old seal spent his last years on our coast and in 2021 became the mascot of the voluntary seal guard and received a lot of press attention. The solitary Bottlenose dolphin, which has been turning up regularly in our waters for many years and often seeks out the company of divers, also makes an appearance in the report.

2021 marked the 75th anniversary of the International Whaling Commission. Whether there is a reason to bring out the champagne, you can read in an opinion piece.

Report of 2020

As usual, the Royal Belgian Institute of Natural Sciences (RBINS) has published an annual report on strandings and observations of marine mammals and other protected marine species in Belgium. It summarises the results of research and monitoring in 2020.

In 2020, 65 harbour porpoises washed ashore, a relatively low number compared to most recent years. Since 2002, only four years had less, and in some years there have been more than 100 washed up specimens. Some live porpoises died shortly after being stranded. The main cause of death of the animals that were studied was predation by the grey seal, a phenomenon that was first described only in 2012.

43 seals washed ashore dead or dying. This was comparable to the previous two years, but significantly more than in the years before that. Incidental catch was the main cause of death in the stranded seals. Sealife took care of 16 seals in distress. Apart from the well-known resting places in the IJzer estuary and the marina of Nieuwpoort, 2020 saw the emergence of a new haul-out site for seals (both harbour and grey) in Ostend.

The most notable strandings concerned a minke whale and two Sowerby’s beaked whales. The very young minke whale was already very weakened before it broke its mandibles, died and washed ashore. Sowerby’s beaked whales do normally not inhabit the North Sea and are only seen here very rarely. The most spectacular catch in 2020 was that of a leatherback turtle: the crew of a coastal fishing vessel was able to return the animal to the sea unharmed.

In addition, the publication also contains information on the increasing monitoring of seals by volunteers, on the analysis of porpoise stomach contents, and on the possible role of military sonar in the stranding of some beaked whales.

Report of 2019

The Royal Belgian Institute of Natural Sciences (RBINS) has been responsible for coordinating research into the strandings and cause of death of marine mammals in Belgium since the early 1990s. Information on observations at sea is also collected. With the collaboration of SEALIFE Blankenberge and the Universities of Liège and Ghent, RBINS has, as it does every year, brought together the available data in a report.

In 2019 51 harbour porpoises washed ashore: a low number compared to previous years. More than half of these animals were in a far state of decomposition, and often the cause of death could no longer be determined. Four porpoises had ended their lives as bycatch, four others as a result of predation by a grey seal. The estimated density of harbour porpoises at sea in June and August was about the average of previous years. The only other cetacean found stranded was a highly decomposed common dolphin. As in 2018, a solitary, social bottlenose dolphin was present for months in the area bordering French waters. In addition, a group of bottlenose dolphins was observed twice. More exceptional were the sightings of a humpback and a minke whale.

The presence of seals on our coast is still on the rise; in the port of Nieuwpoort there is now a permanent resting place which is often used by more than 10 harbour seals. Grey seals also seem to be becoming more common. This translates into increasing numbers of dead and dying seals on the beach: 47, the highest number ever recorded. SeaLife took care of 11 Grey and 15 Common Seals.

In 2019, two leatherback turtles and some sunfish were observed. Their presence was possibly related to an unusual influx of Atlantic water. The exact species to which a stranded sunfish belonged is still under investigation.

Marine mammals are very popular: some temporary or permanent exhibitions were opened in 2019, and the skeleton of a sperm whale that was washed ashore in 1989 was excavated with the aim of preparing and exhibiting it. Finally, the report also contains editorials on underwater noise and porpoises, the international dimension of marine mammal research, some well-known seals in Nieuwpoort, and extreme fluctuations in the weight of seals.

Report of 2018

As every year, RBINS has collected data on marine mammals in Belgium. For 2018, this happened with the cooperation of SEALIFE Blankenberge, the University of Liège and Natuurpunt. In 2018, 134 marine mammals washed ashore dead or dying in Belgium, concerning 89 harbour porpoises, 1 white-beaked dolphin, 1 fin whale, 18 grey seals, 11 harbour seals and 14 seals that were not identified to species. In addition, SEALIFE Blankenberge took 30 seals into care: 17 grey and 13 harbour seals (the highest number of grey seals ever, and for the first time more grey than common seals).

Ten percent of the harbour porpoises for which the cause of death could be established had died from drowning in fishing nets, and 30% from predation by grey seals. The fin whale, an 18-metre-long male found dead at sea, presumably died from a natural cause. The number of stranded dead and dying seals (43) was the highest number ever. Six of the grey and one of the harbour seals were believed to have died from incidental capture. One grey seal died entangled in a piece of nylon rope, and another choked on a flatfish.

The most striking sightings in 2018 concerned very high numbers of harbour porpoises in April (estimated at almost 20,000 in the Belgian waters, based on aerial counts) and the relatively frequent occurrence of bottlenose dolphins.

The annual report also contains editorials about the sense and nonsense of taking seals into care, the impact of waste on marine mammals and the use of the port of Nieuwpoort as a resting place for seals.

Report of 2017

The newest marine mammal report presents an overview of marine mammals and remarkable fish in Belgium in 2017. It also focusses on the causes of death of beached animals and the revalidation of animals that were taken into care, and contains opinion pieces about Arctic climate refugees and the grey seal in our coastal waters.

In 2017, the number of stranded harbour porpoises more or less equalled the average of the past 10 years. Nearly 60% of the 93 harbour porpoises that stranded along the Belgian coast in 2017, died due to predation by the grey seal or incidental catch.

Two observations of white-beaked dolphins were documented in 2017, while bottle-nosed dolphins were reported more regularly. Also one deceased individual of both these species washed ashore. A dead minke whale floated through Belgian waters, and eventually washed ashore in the Netherlands.

With 10 common seals, 8 grey seals and 19 non-identified seals, the number of dead or dying seals exhibits a rising trend. Additionally, 22 common and 6 grey seals were taken into temporary care at SEALIFE Blankenberge. A remarkably high number of seals that had been injured by fishing hooks was observed in the port of Nieuwpoort.

The bowhead whale that stayed off the coastal towns of Ostend and Middelkerke on 31 March and 1 April was the first ever to be reported for the entire North Sea. Barely a year after the stranding of a narwhal, the sighting of this animal, of a species that inhabits very northerly waters, instigates a lot of speculation about the effects of climate change on marine life in the Arctic, and perhaps at a global scale.

Report of 2016

The newest marine mammal report presents an overview of marine mammals and remarkable fish washed ashore in Belgium in 2016. It also focuses on the causes of death, revalidation and release of animals that were taken into care, and briefly introduces the research on the influence of offshore windmill parks on the harbour porpoise.

The most remarkable stranding of 2016 undoubtedly concerned a narwhal, an Arctic animal that was last observed in the North Sea almost 70 years ago. Also two humpback whales were seen, and a basking shark and two ocean sunfishes washed ashore.

With 137 animals, the number of harbour porpoises that washed ashore was again very high. The major causes of death were incidental catch in fishing gear and predation by grey seals. Harbour porpoises were shown to avoid an area up to a distance of 20 km during the construction of offshore wind turbines.

White-beaked dolphins were reported on one day only, in contrast to bottlenose dolphins that were regular and prominent guests again. In April a severely decomposed male bottlenose dolphin washed ashore, followed by a heavily decomposed dolphin along the Scheldt a few days later. The species could not be determined anymore.

The number of strandings of dead and dying seals remained similar to previous years: six harbour seals, 11 greyand 12 unidentified seals. SEA LIFE Blankenberge took care of record high numbers: 15 grey and 24 common seals,including an albino animal. No less than 12 grey and 20 common seals could be returned to the wild after revalidation.