Fish resource restocking in Latvia

by Thomas Jensen
Baltic salmo salar juviniles

Century-old activity gets a makeover

This article was featured in Eurofish Magazine 6 2023.

Currently, we stand at a point, when we must look back, assess our implementation of the long-term fish restocking programme, appreciate where we are today and look ahead, envisage the direction, and take the next steps to maintain sustainable and diverse fish resources in Latvia’s inland waters.

The Institute of Food Safety, Animal Health and ­Environment (BIOR) is currently the most significant juvenile fish producer in the Eastern Baltic region, primarily fulfilling the state’s fish resource restocking programme. Every year, the institute releases juveniles and fry of various fish species into Latvian public waters. The most important species that supplement natural stocks are salmon, sea trout, vimba, river lamprey, and pikeperch.

Restocking helps to maintain natural stocks of fish

Every year, the state fish farms, Tome, Karli, Dole, and Pelci, release an average of 700,000 one-year-old salmon smolts, 260,000 one-year-old sea trout smolts, 16,000 two-year-old sea trout smolts, and 1,140,000 ­pikeperch, vimba, and whitefish fingerlings. In addition to the mentioned species, the institute is also involved in releasing eel and periodically restocks pike. Among other countries, ­Latvia is unique because each year natural stocks are supplemented with approximately 13,000,000 river lamprey fry. Migrating lamprey spawners are translocated upstream across the dams to the areas with natural spawning sites. Besides, the institute participates in the reintroduction programme for Baltic sturgeon, Acipenser oxyrinchus. For private Latvian aquaculture companies and pond farms the institute raises rainbow trout, sturgeon, pikeperch, and carp fingerlings. The current scale and quality of juvenile production did not appear overnight but have been achieved through prolonged work and knowledge transfer through generations of scientists and practitioners.

The centenary of the Tome Fish Farm approaches

The Tome fish farm was ­established in 1929 after the reorganisation of the previously fragmented structure of the sector. At that time, Latvia had a planned comprehensive national electrification plan as an interest in the preservation of salmon stocks. The state established Tome fish farm near the planned hydroelectric power station site Ķegums. Initially, the farm used water from the Pruupe spring, later water was drawn from the Licupe River, but since 1984 the Daugava River via the HPP reservoir has served as the natural water source for the nursery. An interesting aside is that in the early 1930s, when the main means of transportation were trains, horse-drawn carriages, and the first automobiles, Latvian fish farmers exported salmon and whitefish eggs to supplement wild fish stocks as far away as ­Germany, Netherlands, and France.


A century ago, salmon and sea trout were only raised till the fry stage. It took significant and prolonged scientific work to understand how to grow the fish to larger sizes. Initially, the focus was on raising them till the fingerling stage and then till the smolt stage. Salmon have always been, and still are, a resource of national importance in Latvia. The state supported research to find out how to compensate for the loss of migratory fish resources due to the planned ­construction of the Daugava hydroelectric power stations. The breakthrough in farming occurred approximately fifty years ago when granulated fish feed KRT was invented. This innovation coincided with the completion of the last Daugava hydroelectric power station, Riga, resulting in a significant leap in the rearing of salmon and grayling juveniles. The institute interrupted the release of fingerlings and shifted to the large-scale release of salmon at the smolt stage, i.e., to the stage that is ready to migrate to the sea.

The hydroelectric power station Riga started operating in 1974, and in 2024, the fiftieth anniversary of the artificial maintenance of the Daugava salmon population will be celebrated. For almost 50 years, the fish farms Tome and Dole have successfully maintained the Daugava salmon stock. Latvian salmon have preserved their homing instinct, they recognize their native river, and continue to return to spawn in the Daugava River. Here they are caught by fishermen, farmers perform fertilisation, and eggs and fry are reared on the fish farms. After approximately two years, the reared juveniles are released into the Daugava River to perform their feeding migration to the Baltic Sea.

Rearing needs to adapt to the challenges it faces today

While juvenile rearing methods developed in the last century have proven their sustainability, they need to be adapted to the requirements of this century, considering changes in wild fish populations, in stock management, in the environment, and in climate patterns. The extended warm season and increased water temperature in the Daugava River prolong the period of pathogen activity. Although this leads to an increase in fish illness, the aquaculture sector must reduce its use of antibiotics and the discharge of these medicines into the environment. The development of antibiotic resistance in bacteria is a significant problem today, not only in the aquaculture sector but also in other agricultural industries. These are among the challenges Latvia is currently facing and studies are needed on how to adapt production, introduce new innovative solutions, preserve the stock, and continue to breed and release healthy fish juveniles.

New aquaculture centre to develop innovative solutions

With funding from the European Maritime, Fisheries, and Aquaculture Fund (EMFAF), a national Aquaculture Innovation Infrastructure Centre is being constructed and will be equipped with the latest technologies. The building will house eight different experimental recirculating systems for broodstock maintenance, egg incubation, fry rearing, juvenile feeding, and fish juvenile rearing. The centre will not only meet nearly zero-energy building standards but will also be equipped with solar panels. Heat pumps will provide heat for fish farming. It will be an example of sustainable and innovative solutions that will contribute to changing the direction of water ecosystem management.

The design and construction of the Aquaculture Innovation Centre in an area of 1,540 square meters is being undertaken by a local firm, while a company from Malta develops the technology project and supplies fish-rearing equipment and apparatus. Construction of the centre should be completed by the end of 2023, when the systems will gradually be implemented and fish fry rearing started. The plan is to start with the incubation of pike-perch and adapting its rearing methodology to Latvian conditions, as it is a species that is important for the aquaculture industry. In addition, the rearing of juveniles of carp and other species will continue.

However, more information will be provided when the recirculation centre is completed, when the tanks are installed, the feeding systems are connected, when water is introduced into the system, and when the fish fry rearing process is started.

Dr Santa Purviņa
Senior Expert, BIOR

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