Over the last 45 years, the annual landings of the North Sea herring have varied between 11 000 and 1.2 million tons.
The year-classes 1998 and 2000 were strong, while the year-classes from 2001 are estimated to be among the lowest recorded. Having this many poor consecutive year-classes is rare, and it is particularly important that the management ensure the safety of the spawning stock in the next years. It is thus recommended to reduce the fishing mortality on the adult and the juveniles in order to bring the spawning stock biomass back to the Bpa (precautionary approach).
Management technical regulations of the fishery
For management of North Sea herring it is recommended to consider the stock of Western Baltic spring spawners mixing up with the North Sea herring in Skagerrak. North Sea herring is widely distributed throughout the North Sea and Skagerrak-Kattegat.
The North Sea herring is managed according to the EU-Norway Management Agreement from 1997, revised in 2004. Quotas are set for the directed fishery and for by-catches in other fisheries with the aim of minimizing the by-catch of immature fish. The agreement sets limits for maximum fishery mortalities (0.25 for adults and 0.12 for juveniles) when the spawning stock is above 1.3 million tons (Bpa). The revised agreement includes a TAC (total allowable catch) change limit of +/-15 per cent.
In the present situation, where four consecutive weak year-classes are recruiting to the population, the 15 per cent rule is considered inconsistent with the Precautionary Approach. This rule might be consistent with the precautionary approach in situations where the manager departs from the rule early enough to secure the development in the stock.
The EU has a quota for by-catch of herring in the industrial fisheries while by-catches of herring taken in Norwegian fisheries are allocated against the quota. Norway has 29 per cent of the annual TAC. Part of the international catch control system has not been fully efficient, and unreported catches in excess of quotas have been revealed for the years 2002-2004. International efforts are made to solve these problems.
The fishery in the coastal fisheries is regulated with maximum quotas.
Ecosystem/Biology
It requires specific bottom substrate for spawning, from coarse gravel to small stones, where the eggs are attached. It reaches maturity at the age of three to four years. The number of eggs produced by the female varies from 10 000 to 60 000, depending on the length of the fish. The main spawning grounds are in the Shetland-Orkney area and off the Scottish east coast, where spawning takes place from July to September. The larvae are transported by currents into their nursery areas in the North Sea and Skagerrak/Kattegat where they stay during the first one or two years of their life. Herring is mainly a plankton feeder (calanoid copepods and krill) but will also take small fish like sprat and sand eel. Larvae and immature herring are important food for other species.
About the fishery
Herring is caught in a directed fishery by purse-seiners and trawlers and as by-catch in the industrial fishery. The Norwegian fishery is mainly by purse-seiners. The fishery is most intense in the second half of the year, aiming at the mature and spawning stock component.