After forty years you can call him ‘the cormorant expert in the Netherlands’. Ecologist Mennobart van Eerden remembers well how it all started. Commissioned by Rijkswaterstaat, he made bird inventories over the IJsselmeer area with a small plane. There were, among other things, grebes, tufted ducks and nuns. And cormorants, then scarce. Van Eerden became fascinated by the prehistoric-looking bird. That dragon’s head, that scaly plumage: it doesn’t take much imagination to see in the cormorant the missing link between bird and dinosaur. It is a common theory that birds are genetically descended from dinosaurs.
So the cormorant. For laymen: that is the large black figure that you often see sitting on lampposts along the highway with outspread wings. Because it has little fat on its feathers, the water bird has to dry up after a swim. He does this by blow-drying his outstretched wings by the wind.
‘A beautiful bird’, Van Eerden calls him. Where some see a coal-black creep, the ecologist reflects on the beautiful red corner of the mouth in breeding season, the white spring spot on its thighs, the fascinating hooked bill, the white headdress. ‘Standing on the edge of a colony of cormorants is a fantastic experience. You can go to Peru, but we also have such large bird colonies in the Netherlands’, says Van Eerden.
It is an intelligent bird, says the expert. ‘As soon as cormorants are shot at somewhere, they become more shy. The bird is always on guard. He has good eyes, with which he sees through things, as it were. If you look from a shelter, every bird gets used to that motionless thing at some point. The cormorant looks into the peephole and sees your every move.’
Fewer breeding pairs
Certainly not everyone shares Van Eerden’s enthusiasm. The cormorant eats fish and its white poo stinks and defoliates the trees in which the groups breed. ‘And it’s black too’, says Van Eerden, who is convinced that the bird would have a better image if it were as innocently white as the much more popular egret or spoonbill.
Fishermen in particular can shoot the cormorant, and not for the first time. The animal was almost extinct in the last century, as a result of hunting, agricultural poisons and polluted water. It has been protected since 1965. The water quality also improved, as did the fish stock.
The bird subsequently prospered so much that commercial fishing is seriously hampered. At least that’s what fishermen claim. They have been pushing for measures for decades, followed by politicians who pick up on that noise.
On 11 May, the European Parliament’s Fisheries Committee held a hearing on the cormorant. Peter van Dalen, MEP for the Christian Union, dedicated one afterwards podcast at.
He was, he says, affected by the problems in Sweden, Croatia and Italy, among others. According to a Danish researcher, grayling and cod in particular are threatened with extinction because cormorants eat the young growth and, moreover, their group hunting behavior drives the fish in such a way that it also succumbs to stress. Result: less algae-eating fish deteriorates the water quality and thus the biodiversity. According to Van Dalen, the ecosystem can no longer cope with the large populations of cormorant. Time for tough measures from the European Commission, according to the politician.
Remarkably enough, the facts are exactly the other way around, says ecologist Van Eerden. At the last count, on 17 May, observers like him counted 1,712 nests in seven colonies in the IJsselmeer region. ‘A historically low number, not seen since 1970’, says Van Eerden. At the Oostvaardersplassen, once the largest colony in the Netherlands, the bird is as good as extinct.
The picture over the years: it started in the 1970s with a single colony near the Naardermeer, after which the cormorant spread as a breeding bird over the entire coast and the IJsselmeer, including inland waterways and cities. Between 1995 and 2010, the numbers of breeding pairs fluctuated between 10,000 and more than 12,000 in the IJsselmeer region alone. Thereafter, a decline set in, with a temporary rebound between 2016 and 2018, probably due to the explosion of the round goby – an exotic species from the Danube basin that drove out the ruffe. Van Eerden: ‘Since 2019 there has been a free fall, now the number of breeding pairs no longer exceeds 2,000.’
Sovon . research organization reports nationally a ‘significant decrease’ of about 5 percent during the last 12 years. Just over 16 thousand breeding pairs are counted annually; in winter there are more people than in the past on Dutch waters. The balance: more colonies, fewer birds.
Hardly a threat
Does the cormorant eat the catch of the commercial fishery? Hardly any, says Van Eerden. After analyzing thousands of pellets, he was able to determine the cormorant’s menu. The type and size of the fish eaten could be deduced from hearing stones. It turned out that the cormorant mainly eats small fish, up to 25 centimeters long. Despite its name, it does not mainly eat eels (now critically endangered), but smelt, ruffe, bass and roach. Hardly a threat to fishermen.
This is in contradiction with photos that regularly appear of cormorants almost choking on a large eel, sea bass or tench. These are exceptions, says Van Eerden, used for imaging. ‘In reality, his menu mainly consists of bulk varieties, of which there is more than enough. Where the fish stock is declining, the cormorant has long since left. In stages before that, cormorants immediately give birth to fewer young. Diving fishing is also a top sport: it is only efficient as long as there is a lot of food’.
According to Van Eerden, it is difficult to prove damage to fisheries by cormorants. ‘It is often much more complex and there are completely different causes for the decline in fish stocks. Such as water quality, damming or channeling waters or silting up which, for example, made it difficult for the salmon.’
Measures vary from chasing to hunting. In Norway, the bird is still shot and eaten. ‘A slightly watery taste’, Van Eerden heard from Noren. In Denmark eggs were oiled, after which they no longer hatch due to lack of oxygen.
Pointless, according to Van Eerden: where voids arise, they are quickly occupied by new ones. He argues for ‘coexistence’, based on sustainable fishing. According to him, a lot can be achieved by improving the living conditions of the fish. And with reflection on the philosophical question of who the fish actually belongs to: is it man alone, or part of nature? Van Eerden knows the answer.