Fish: fry stocks in the North Sea, 1980-2002
The size of the fry stocks of four commercial fish species: sole, plaice, cod and herring. By contrast with the biomass of cod, the fry stocks of herring have, in recent years, recovered due to the catch restrictions that have been introduced.
Plaice, Herring and Cod
In 2002, plaice and cod fry stocks were below the precautionary level (300 and 150 million kg respectively). Cod stocks give the greatest cause for concern: for over fifteen years the biomass has been below the precautionary level and has hovered around the limit level (65 million kg) for the last ten years.
Herring stocks have recovered in recent years and the biomass of this species has returned to above the precautionary level since 2001. This recovery is a result of a few strong year classes (1998, 2000) and the measures taken in 1996, when the total allowable catch for herring was halved and a maximum was introduced for by-catches of this species for the fishing industry.
Following the strong 1996 year class for plaice, this species has recovered slightly following a prolonged decrease from the early 1990s as a result of excessive fishing pressure.
Sole
The sole situation is not bright. Since 2001, the fry stocks have been just above the precautionary level (35 million kg). Intensive fishing pressure meant that the strong year classes in 1987, 1991 and 1996 were rapidly exhausted. As a result, in the mid-1990s, the stocks of fry fell sharply to 23 million kg in 1998. Following the strong 1996 year class, the biomass increased again to 43 million kg in 1999 but pressure from fishing resulted in a fall in 2002 to 32 million kg.
Relevance
If fishing is to remain a sustainable industry, there must be sufficient adult stocks to ensure sufficient offspring each year (fry stocks). In order to manage fish stocks, two limits have been determined for the size of the fry stocks: the limit level and the precautionary level. If the stocks of fry for a particular species fall below the limit level, the production of sufficient offspring is endangered. In order to prevent the stocks of fry falling below the limit level, a precautionary level has been agreed. Above this level, populations can recover, even after a series of bad years. The biological advice aims to raise the stocks of fry at least up to, and preferably above, the precautionary level.
Technical note
The graphs for plaice and sole describe the North Sea (ICES IV). The graph for cod shows developments in the North Sea, including Skagerrak (section of ICES IIIa) and the eastern section of the Channel (ICES VIId). The figures for herring relate to the North Sea, including Skagerrak, Kattegat (ICES IIIa) and the eastern section of the Channel.
References
- ICES (2002). Report of the ICES Advisory Committee on Fishery Management 2002. International Council for the Exploration of the Sea, Cooperative Research Report nr. 255, Copenhagen.
Relevant sections and indicators in the Environmental Data Compendium
Relevant information outside of the Environmental Data Compendium
- More information about fish can be obtained from the International Council for the Exploration of the Sea
