The North Sea
Index section North Sea
- Rare North Sea fish
- Subsection:Guidance Commercial fishery in the North Sea
- Subsection:Guidance Pollution of the North Sea
Introduction
The North Sea is a relatively shallow coastal sea of some 572 000 km2 in area, with the Dutch Continental Shelf (DCS) accounting for 10% of the area (over 57 000 km2). It is thus the largest Dutch ecosystem. Most of the statistics presented in the texts beginning with the code D9 relate to the DCS.
As a result of differences in depth, nutrient reserves, salinity, currents and composition of the seabed, the North Sea has very diverse communities. There are big differences between the shallow coastal zone, up to 20 metres depth, and the open sea. Together with the Waddenzee (Wadden Sea) and Zeeland delta, the relatively warm and nutrient-rich shallow coastal zone has an important function as a spawning ground and nursery for various fish species.
The highest densities of benthic fauna are inshore, where there are dense beds of shellfish. In this coastal zone there has been a sharp increase in certain exotic species, and in species from warmer southern areas. The wealth of fish and benthic animals makes this coastal zone very important for birds, especially for scoters, eider ducks, terns, gulls and divers.
Fishery
The North Sea is one of the world's most important fishing grounds, yielding benthic and pelagic fish, and shellfish. Some species have been overfished, but the herring is one of the species whose stocks have recovered and are currently favourable. Cod stocks, however, are so low that there is a danger that sufficient juveniles will not be produced. Generally, large fish of all species are becoming rarer.
Fishing is affecting other species too. The harvesting of the shellfish spisula from the North Sea is impacting on the occurrence of the common scoter. And fishing is probably responsible for the crash in numbers of rays and for the decline in numbers of harbour porpoise.
Beam trawling for benthic flatfishes is causing high mortality in benthic fauna and a shift in their age composition.
However, birds profit from the large amounts of fish waste dumped at sea by trawlers.
Other uses
The DCS is exploited not only for fishery but also for shipping, oil and gas production, the abstraction of sand, gravel and shells, the dumping of dredged material, land reclamation (Tweede Maasvlakte), the discharge of wastes, and recreation. All these activities affect the occurrence of plants and animals. The rivers that flow into the North Sea from the Netherlands are the most important source of pollution in the sea. Most of the oil pollution, however, comes from shipping. Oil pollution is still a problem for seabirds, although there are fewer casualties.
References
- Bisseling, C.M. (red.) (2001). Met de natuur in Zee. Rapportage project "Ecosysteemdoelen Noordzee", kennisfase. Expertisecentrum LNV. Wageningen.
- Daan, N. (2000). De Noordzee-visfauna en criteria voor het vaststellen van doelsoorten voor het natuurbeleid. Nederlands Instituut voor Visserijonderzoek. IJmuiden.
- Leopold, M.F. en N.M.J.A. Dankers (1997). Natuur in de zoute wateren. Achtergrond document 2c. Natuurverkenning '97. IKC Natuurbeheer. Wageningen.
