Over the last 45 years, the annual landings of the North Sea herring have varied between 11 000 and 1.2 million tons.
ICES classifies the stock as being at full reproductive capacity and as being harvested sustainably. The year classes from 2002 to 2007 are estimated to be among the weakest since the late 1970s. The year classes 2008 and 2009 are estimated to be above the long-term geometric mean, but ICES considers that the stock is still in a low productivity phase.
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.
Herring is an excellent source of vitamins A, D and B12. It has a high content of Omega-3 fatty acids. Exact values will vary according to fat content.
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.
Please have a look at https://herring.fromnorway.com/ for more information about north sea herring.