Fish

It is only in recent years that the fjord’s fish population has been the subject of scientific study, so we are not in a position to give an account of the development of the populations of the various species of fish. Our knowledge comes partly from Poul Hald-Mortensen’s 1992-94 analyses of cormorant casts, and partly from two studies by ‘The Laboratory of Fish Ecology’: one in 1991-93 and 1999 at the northern end of the fjord, and the other in 2000 in the southern part. The Laboratory of Fish Ecology used assorted fishing methods, whilst Poul Hald-Mortensen based his study on analyses of cormorant cast.

The ear stones (otoliths) of fish are not dissolved by cormorants’ stomach acid, and they are also characteristic in different species. Furthermore, ear stones indicate the age and size of the fish. As the cormorant is an opportunist that will eat any fish it can get hold of that is small enough to swallow, its diet can give a picture of which type of fish, in what quantities, are found in its foraging grounds.

Both in number and by weight the three-spined stickleback is by far the biggest presence in the fjord. By weight, herring, brisling, viviparous eelpout, black goby, perch, trout, eel and pikeperch come next, whilst as far as numbers are concerned black goby, brisling, nine-spined stickleback and herring come after the three-spined stickleback.

For fishermen the eel is the most important species but large numbers of trout, herring and garfish are also caught. Garfish are caught mainly early in the summer, when they come into the fjord to spawn. Herring too have known spawning sites at the northern end of Lejre Vig, but they are mostly caught in the deep hole by Herslev. Eel fishing was once a significant industry but commercial fishing is now very limited in extent. There is on the other hand extensive hobby fishing.

The above comments apply primarily to the southern part of the fjord but, with some reservations, can apply to the whole fjord. As we have already said, our knowledge regarding the fish in the fjord is still far from complete.

The fjord’s fish provide food for a wide range of birds. Cormorants are well known for their competition with fishermen for eels, but tern, gulls, merganser and others are also fish eaters. When fishermen empty their nets and throw out the fish they do not want, the big gulls flock around their boats to enjoy the crumbs from the rich man’s table.

The descriptions of the various species are based on The Laboratory of Fish Ecology’s studies of the northern part of the fjord in 1999, and the southern part in 2000. We have only included species which have, in at least one of these studies, constituted at least 10% of the population by either weight or number.