The North Sea is situated to the east of Britain and to the
west of continental Europe. It extends to about 625,000 km2. To the
north, it is bounded by the continental shelf edge marking the
limits of the Norwegian Sea. There is a relatively deep (600 m)
trench off the coast of Norway, otherwise it is generally less than
200m in depth, becoming shallower to the south. The seafloor is
comprised mostly of mixed sediments with mud in some more northerly
areas, and coarser sands in the shallower tidally active south.
Areas close to Scottish and Norwegian coasts are rocky.
In addition to fishing grounds, there are heavily used
shipping lanes (particularly in the south) and exploitation of
extensive reserves of oil and gas beneath the sea floor.
Fisheries
The main demersal fisheries target a mixture of roundfish
species (cod, haddock, and whiting) or flatfish species (plaice and
sole) with a bycatch of roundfish. There is also a fishery for
Saithe. Pelagic fisheries mainly target herring and mackerel. These
are all predominantly for human consumption, although a proportion
of the pelagic fisheries are used for fishmeal and fish oil
production. In addition, there are industrial fisheries for
sandeel, Norway pout and sprat which are used in the production of
fishmeal. Besides these finfish fisheries there are also fisheries
for the crustaceans Nephrops, Panadalus borealis
and brown shrimp (Crangon crangon). Norway, Denmark, UK
and The Netherlands are the major North Sea fishing nations.
Status of the stocks
Information on the status of the stocks has been derived from
the International Council for the Exploration of the Seas (ICES)
who have a commitment to undertake annual stock assessments in
European waters.
North Sea cod stocks are in a very poor state with constant
high levels of fishing mortality in recent years combined with low
spawning stock biomass. Currently the stock is outside safe
biological limits and a zero fishing mortality level is
recommended. A cod recovery plan has been proposed, with the aim of
long term management of the species for the future. In February
2004, the European Union introduced new regulations affecting cod
fishing in the North Sea. The aim is to increase the quantity of
mature fish to more than 150,000t (North Sea, Skagerrak and eastern
Channel) over the next five to ten years. These measures included
controls for the setting of total allowable catch (TAC), fishing
effort limitation (number of days at sea and gear restrictions) and
restrictions on landing ports, stowage and transport of cod.
The stock size of haddock has historically shown large
variations due to the occasional occurrence of a very strong year
class. Although the stock is considered within safe biological
limits, currently it is the 1999 year class alone that supports the
haddock fishery. Until another strong year class recruitment, which
in not predicted for several years, the haddock fishery will
continue to rely on the 1999 year class recruitment for its future.
The status of the whiting stock is unknown, but with declining
landings and poor recruitment in recent years, the stock is
considered outside safe biological limits. Most flatfish stocks are
outside the safe biological limits. Plaice is estimated to be near
the lowest observed level and exploitation rates are considered to
be too high. The development of a recovery plan for this species
has been recommended. For sole the spawning biomass reached a
historic low in 1998 and although some recovery has been observed,
recent recruitment is very poor. The fishing mortality for this
species is also considered to be too high. In contrast to the
previous stocks, the abundance of saithe has increased in recent
years whilst fishing mortality has decreased, and the stock is
considered to be within safe biological limits.
Herring stocks have recovered since the closure of the fishery
in the 1970s and 1980s. Recruitment from several year classes has
been above average, although the 2003 recruitment was poor. The
population is currently thought to be stable in the short term. The
North Sea part of the mackerel stock has all but disappeared; fish
caught in the North Sea now come predominantly from a larger
western group which spawn outside the North Sea and are only
present in the northern North Sea in the second half of the year.
The sandeel stocks have fluctuated with recent recruitment being
amongst the lowest recorded. Consequently the status of the stocks
is very uncertain. Recruitment to the Norway Pout stocks has been
very poor in recent years and landings declined. Since 1995,
landings have fluctuated about a low level. However, the stocks are
thought to be within safe biological limits. The sprat stocks are
considered to be in good condition, with biomass increasing in
recent years.
The Nephrops stocks within the North Sea are
generally thought to be exploited at sustainable levels, and may
even be under-exploited in the northern North Sea. The
Panadulus borealis stocks appear to be stable in some
areas (e.g. Norwegian Deep and Skagerrak) but are uncertain in
others (e.g. Farn Deep and Fladen Ground). Stocks of some shellfish
in the Wadden Sea have been overfished.
Environmental problems
Besides the current parlous state of many fish stocks,
particular environmental problems caused by fisheries in the North
Sea are:
- Non-sustainable bycatch
of harbour porpoises in bottom-set gill nets. Current figures
indicate that more than 2% of harbour porpoises in the
central-south North Sea are caught per year. This is thought to be
greater than the rate of population growth. In addition, there is
an unmeasured bycatch in similar nets fished by Norwegians.
Recently regulations have been introduced by the EC to help combat
this. However, the mandatory use of 'pingers' will only apply to
gear deployed by vessels greater than 12m in length and there will
be no on-board observer scheme for fisheries using 'pingers'.
- Extinction of several species of skate and ray (elasmobranchs) in the southern and central North
Sea.
- Very high bycatch levels in beam trawls and shrimp
fisheries in the south-eastern North Sea.
- Management of sandeel fishing near Shetland and off eastern
Scotland needs to avoid risking depletion of the stocks due to
their importance to seabirds and other predators (including
fish).