Fishery and biology of herring (Clupea harengus L.) in the Gulf of Finland: A review

The herring catch represents two-thirds of the entire fish catch in the Gulf of Finland. Herring reach maturity at a total length of 12–15 cm by the age of 2–3 years. Spawning takes place in May-June along most of the coast. Mass spawning begins when the water temperature is 8–9°C; eggs are usually attached to vegetation. Egg development takes 6–15 days. In recent years the growth of herring has been slow. In the catches, the oldest herring have been over 15 years. In the spring trap net catches, the most plentiful age group are the three-year-olds. In the autumn trawl catches, the most abundant age group is one-year-old herring. The stock is presently exploited around the F0.1 level. Assessing the state of the herring stock in the Gulf of Finland is complicated, because of the spawning and feeding migrations between the Gulf and the Baltic Sea proper.