Artificial reproduction of salmon and sea trout in Latvia has more than 130 years experience. Salmon egg incubation and fry releasing was started by aquaculture specialist Alvins Kirsh (Alvins Kiršs) on 1885. He founded the first private salmon and trout hatchery in Carnikava, first artificially reared salmon fry were released in Gauja River and Daugava River. On 1882 hatchery was transferred to Vecsalaca on Salaca River. On 1893 salmon fry were released in Salaca for the first time. On 1894 35 000 salmon fry were released, on 1895 - 1 220 000, on 1896 - 1 000 000, on 1897 - 1 673 00. On 1898 Riga City council bought 125 000 salmon fry for 600 gold rubles and released them in Daugava River, and its tributaries, Ogre and Perse River. To make fry transportation from Salaca River to Daugava River easier, on 1898 a small salmon hatchery was equipped especially for Daugava River needs on the spring of Riteru muiza. The difficulties of smolt transfer were overcome. On 1909 A. Kirsh continued to rear salmon parr in Vecsalaca filial Berkavina (Salaca River basin), on Daugava River in front of Ikskile. Altogether from 1893 untill 1916 in Lielupe River -368 000, in Daugava River - 2 617 000, and in Salaca River 6 308 000 salmon fry were released (Eglitis, 1939).
In 1930ies salmon artificial rearing concentrated in three hatcheries: Tome, Karli (Kārļi) and Pelci (Pelči), situated in Daugava, Gauja and Venta River basins, altogether yearly released about 3 millions of fry (Mitans, 1975).
In post World War II period fish farms continued their work, and gradually increased their efficiency till 10-12 millions of released salmon fry and parr per year. The necessity to increase productivity was connected with perspective damming of rivers by HPP. It was important to maintain salmon stock and develop artificial rearing of Daugava salmon, because natural salmon from Daugava constituted 70-80% of Soviet fishermen catches at that time.
After Daugava River damming by HPP Riga, the main salmon river of Latvia loosed natural migratory fish breeding facilities. Therefore, the question of artificial rearing and salmon population maintenance was solved by reconstruction of state hatcheries to maintain salmon fisheries sector. Besides, to maintain natural salmon spawn and other natural values, the biosphere reservation was gradually established in Salaca River basin (Malikova, 1966). From 1970-1975 state hatcheries of Latvia released 423 000 till 735 400 salmon smolts yearly (Hasina and Orlova, 1976).
Today artificial reproduction of salmon and sea-trout resources is implemented in accordance with the National Artificial Fish Resources Reproduction Program Guidelines.
The main principle of the Guidelines is to maintain the salmonid fish homing reflex. The catch of the salmon breeders takes place in rivers or their mouths and the water from the same river is used in the fish rearing. Today Research Institute "BIOR" is responsible for salmon and sea-trout reproduction in Daugava, Gauja and Venta, altogether releasing 1.25 millions of salmon and sea trout parrs and smolts.
For over 70 years the salmon population in Daugava River has been maintained artificially, proving that the artificial maintenance of the salmon stock in Latvia is successful, as Daugava River salmons continue to return for spawning in their native river for decades.
Eglitis, P., 1939. The beginning of artificial Fish breeding in Latvia. Fisheries monthly magazine, 4: 159-161 (in Latvian).
Hasina, G.M., Orlova L.E., 1976. Production of salmon juveniles in fish farms of Soviet Baltic States. Artificial rearing of Rainbow trout and Baltic Salmon. Riga, Zvaigzne, 40-53 (in Russian).
Malikova, E., M., 1966. The question on maintenance of valuable fish stock and fishery sector after regulation of Daugava. Fisheries research in Baltic Sea Basin. Riga, Zvaigzne, 1: 61-75 (in Russian).
Mitans, A. 1975. Efficiency of natural and artificial production of Baltic Salmon, as a result of peculiarities during its freshwater life period. Fisheries research in Baltic Sea Basin. Riga, Zvaigzne, 11: 110-152 (in Russian).