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Monitoring of Baltic herring populations secures the catches of our largest fish resource in the long term

In recent decades, 50–80 per cent of the fish catches in Finland have consisted of Baltic herring and sprat caught by commercial fishers. Natural Resources Institute Finland (Luke) annually monitors the state of Baltic herring populations in its main fishing areas of the Gulf of Bothnia and the Baltic Proper as part of the EU’s data collection and the ICES advisory process. Annual fishing quotas are defined based on the data. Through the quotas, it has been possible to guide the fishing of Baltic herring so that the stock is not endangered in the long term.

The Council of the European Union is responsible for defining area-specific and species-specific fishing quotas for the part of the Atlantic belonging to the EU and the coast of the Baltic Sea. The quotas are based on advisory opinions provided by the International Council for the Exploration of the Sea (ICES), in which fish stock monitoring data produced by EU countries are used.

Luke’s participation in the collection of data is essential for the evaluation of the Baltic herring population in the Gulf of Bothnia with Swedish parties. Newer and better fish population models have been adopted in the population evaluation.

There has been no collapse in the Baltic herring population while the monitoring has continued.

Determining limit values for the sustainable fishing of the Baltic herring population in the Gulf of Bothnia using the ICES standard methods has been more difficult than usual compared with other fish populations being evaluated. The fact that a collapse of the population has never been documented may have contributed to this. However, the highest possible levels of fish catches were probably seen in the 2010s.

A trawling team working. On the left, Toni Nikaniemi, fishing entrepreneur; in the centre, Roope Lehmonen, research engineer (Luke); and on the right, Hannu Harjunpää, research engineer (Luke). Photo: Riku Helisevä / Luke. Photo: Riku Helisevä / Luke.

Most of the Baltic herring catch in Finland is caught under the Gulf of Bothnia quota. At their peak in the 2010s, the Baltic herring quotas and catches in the Gulf of Bothnia were above 100,000 tonnes. They started to decline towards the end of the 2010s. In recent years, the catch in Finland has been around 60,000 tonnes. 

Baltic herring and sprat are caught in the Baltic Sea mainly by trawling. In typical mixed fishery operations, both are caught in the trawl at the same time. In the Gulf of Bothnia, the catch is almost exclusively Baltic herring, as there are small amounts of sprat in the area. In the Gulf of Finland and the northern part of the Baltic Proper, sprat has been abundant since the 1990s, while the eastern cod population in the Baltic Sea has been in a weak state. A few per cent of the Baltic herring catch is caught in the spring and early summer with trap nets on the coast.

A small part of the Baltic herring and sprat catch caught by Finnish commercial fishers is sold fresh and processed for human consumption. The most is currently used in fish feed production. Baltic herring is also sold in Finland as feed for fur animals and abroad as feed for farmed fish.

In the eutrophic Baltic Sea, the fishing of Baltic herring and sprat is the most effective individual method of removing nutrients that have already reached the sea. Fish feed made from Baltic herring is also used in rainbow trout farming with the aim of decreasing the rainbow trout’s nutrient load on the sea through an internal nutrient cycle.