The degree of taxation of a fishstock is usually described by the fishing mortality coefficient. This expresses how much of a year class is caught in relation to the total number of the year class at any time.
Herring is a key species in several marine areas.
These fish consume large quantities of plankton organisms and are themselves an important source of food for organisms higher up in the food chain. The taxation of North Sea herring increased considerably during the 1960s. In 1965, the catch amounted to more than 1.4 million tonnes. The North Sea herring was severely over-exploited during the 1960s and the 1970s. During the 1980s the stock of North Sea herring was partially restored, and fishing was resumed.