Atlantic herring (Clupea harengus) is widely distributed in the Northwest and Northeast Atlantic. Within the Northeast Atlantic, they are distributed from the northern Bay of Biscay to Greenland, and east into the Barents Sea. In the Northwest Atlantic they are distributed from South Carolina to Labrador. Adult fish are pelagic and are found mostly in continental shelf seas to depths of 200 m deep.

Herring is numerically one of the most important pelagic species in several North Atlantic ecosystems and intensive exploitation goes back several centuries. Stocks have fluctuated enormously in the past. The Baltic herring is sometimes considered as a subspecies of the Atlantic herring (Clupea harengus), adapted to brackish water. The Baltic herring grows more slowly and has a lower fat content than the Atlantic herring.

The Bothnian Sea (SubDivision 30) and the Bothnian Bay (SD 31) stocks are assessed separately. The stock boundary is set between Sub-divisions 30 (Bothnian Sea) and Subdivision 31 (Bothnian Bay) 63o 30’ N. Migration between both SD is now considered to not be truly understood. ICES (2013a,b) considers that the stock structure is still uncertain and more research is required. In the Bothnian Sea there are two spring-spawning coastal populations along the west and east coasts assessed jointly (Lassen, 2011; ICES, 2013a,b).

Atlantic herring stocks have suffered heavily from over-fishing. Baltic herring stocks have, however, not collapsed despite the high fishing effort. Stocks have probably been protected by the fact that the Baltic herring spawns widely in shallow water and also that the catch consists mainly of adult fish.

Since mid-1970s, the fishery has been dominated by trawl fisheries with small vessels (< 12 m) and trapnet fisheries. Since 2000, only a few trawlers (all < 20 m) have been operating in the area. In 2013, trawl fisheries accounted for about 91% of the catches.

Measured by both the amount and value of the catch, the herring is the most important target of commercial fishing in Finland. The total annual catch of all Baltic Sea countries was less than 100 000 tonnes until the mid 20th century. 

Pelagic trawling is used to exploit Baltic herring stocks in the Baltic Proper, the Archipelago Sea, the Gulf of Bothnia and the Gulf of Finland. Only few vessels target sprat directly, but sprat is the main by-catch in Baltic herring fishery. Usually, Baltic herring fishing is conducted as single trawling.