Baltic herring is the main catch of commercial fishing
The so-called Baltic herring is a smaller-growing form of the much larger Atlantic herring. Due to the brackish water conditions in the Baltic Sea, Baltic herring grow more slowly than their oceanic counterparts.
Although the Baltic herring (Clupea harengus) is often considered a biological subspecies of Atlantic herring, their actual relationship is not as simple. For example, compared to Baltic herring which spawn in the spring, autumn-spawning Baltic herring are more closely related to Atlantic herring which also spawn in autumn. Currently, the stocks of spring-spawning herring are dominant in the Baltic Sea.
Baltic herring is a shoaling fish species of the open sea that feeds on zooplankton and
benthic crustaceans, such as mysid shrimps and amphipods. Occasionally they also eat juvenile fish, even their own. Herring spawn in large shoals in May-June, depositing their fertilised eggs onto the stony seabed and the aquatic vegetation. In some places, eutrophication has prevented spawning on the traditional spawning grounds. The herring juveniles often stay for a year or two near the coast, eating zooplankton, and then move offshore to the open sea.
The most important herring stock in Finland is found in the Gulf of Bothnia, which accounts for 70-80% of the country's annual commercial fishery catch. Based on an evaluation of the entire area, other important sources of Baltic herring for Finland are the stocks of the Baltic Sea Proper and the Gulf of Finland, which are fished by most of the Baltic Sea coastal states. From experience, fish population assessments handled as separate units of herring stocks or as combinations thereof, have been found to work well.
Dioxin- and PCB levels in herring have fallen by half since
the turn of the millennium
The concentrations of dioxins and PCBs (polychlorinated biphenyls) in Baltic herring have grown so high in the past decades that except for Finland and Sweden, the EU banned the sale of herring over 17 centimetres for human consumption. One important criterion was the beneficial effects of consuming herring: despite the higher than average levels of dioxins and PCBs, professional coastal fishermen were found to be on average healthier than the rest of the population, due to eating large amounts of fish! The concentrations of PCBs and dioxins have since fallen to less than half, and only the largest herring specimens, i.e. over 18 centimetres, contain environmental toxins slightly above EU limit values.
The majority of the Finnish herring catch ends up as animal feed or goes to factories that produce fishmeal.
Finnish herring fishing was awarded an MSC-certificate
The Finnish herring fishery was awarded an MSC (Marine Stewardship Council) -certificate in 2018, which recognises sustainable and environmentally friendly fishing. Herring fishing also removes a significant amount of eutrophic nutrients from the Baltic Sea every year.
However, thus far, herring has not returned to being a central part of our diet as it was in the past: only 15% of Finnish herring catches are for human consumption, and these are largely for export to Eastern Europe. Most of the catch goes directly to animal feed or to fishmeal factories, where it is used to produce fishmeal which has been cleaned of environmental toxins. This fishmeal is used as a raw material, e.g. for rainbow trout farming.