Seal Death on the North Sea

The seal is a sociable animal. So much so, that virus’ have little trouble spreading fast among seal populations. Indeed, in 1988, the Phocine Distemper Virus (PDV) cost the lives of 18 000 seals on Germany’s North Sea cost, some 60 per cent of the area’s seal population.

There are now fresh signs that this nightmare may see an unwelcomed revival.

Repetition of a nightmare

The first dead seals to have been discovered with the lethal virus since 1989 were discovered earlier this year in Kattegat, just off the Danish island Anholt. It is an exact repetition of the virus’ first showing up, 14 years ago.

As the PDV virus befalls lungs and respiratory organs, infections with bacteria follow. Parasites spread easily to other body organs. The seal dies a slow, and painful death.

The origins of PDV are still a mystery. But also why it has befallen Anholt for the second time, too. Scientists say it may have been carried to the area by a single animal from the open sea, or could have its origins in waste water from nearby mink farms.

One thing, however is sure: the seals here do not have the necessary antibodies. Indeed, the North Sea seal’s population are defenceless against this relatively new epidemic.

Driven to far waters

In 1900, 37 000 seals lived in the North Sea’s mud flats. 1988's epidemic was the first to have been reported since then.

Scientists believe the first epidemic was sparked by arctic seals, looking for nutrition way beyond the boundaries of their natural habitat, suffering from Russian and Scandinavian overfishing.

Arctic seals may look much like their North German counterparts. But they have one – vital – difference: arctic seals are able to live with the PDV virus.

Without the necessary antibodies, and in addition, weakened by a steady increase in marine pollution, these animals now stand little chance of survival.

Even the discovery of a serum, sparking fresh hopes, has proved no remedy. As the serum must be injected into muscle tissue, it would only be of help at seal stations. Injecting 20 000 seals in open nature is practically impossible.

No natural selection

The animal front is becoming increasingly divided by the discussion over the virus. Some say the virus is natural selection. Others, such as those at the National Park in Tönningen, say seals’ normal natural selection follows the classic hunter-prey situation: Is fish in abundance, then the seal population grows. Is fish scarce, then females do not reproduce.

The fishing industry says the size of the seal population has grown up to 20 000 animals. If this was so, experts point out, the seals would both be leaner, and more prone to illness.

However, this is not the case. The animals are all in a healthy condition, there are no signs of over-population, and therefore no obvious need to decimate the group.

Weakened by pollution

What scientists have found, however, is a close link between the virus, and high levels of pollution.

Recent thyroid examinations on dead North Sea seals show severe thyroid damage, coinciding with reports of seals from areas off the North German coast containing 17 times the amount of immune system damaging PCBs than their counterparts in Iceland.

According to seal expert Günter Heidemann from Kiel, "the virus alone was not responsible for the seal epidemic in 1988". "It was also the immunodeficiency, resulting from high pollution levels", he told the Frankfurter Allgemeine am Sonntag.

Already, local administration is bracing itself. However, local crisis management is reduced largely to one thing: the removal of carcasses.