Abstract
Artificial propagation of salmonids in Latvia has a long-standing history, spanning nearly 140 years, periodically interrupted and resumed after the First and Second World War. Between 1939 and 1974, a cascade of three hydroelectric power plants was built on Latvia’s most important salmon river, the Daugava, thereby preventing access to spawning areas. To maintain salmon stocks at an economically significant level, a scientifically based restocking programme of salmon stocks has been established and continues to this day. Over the years, salmonid rearing techniques developed, initially growing them to the larval stage, then to the juvenile stage, and finally to physiologically mature, saltwater-adapted smolts. The artificial propagation of salmon was not interrupted even during the collapse of the Soviet Union. To compensate for the loss of salmonid resources, the Institute of Food Safety, Animal Health, and Environment BIOR performs salmonid rearing, supplementing natural fish stocks with more than one million salmon and sea trout juveniles annually. The salmon stock in the Daugava River basin has been successively artificially maintained for more than fifty years, and the national restocking programme supports salmon stocks in the Gauja and Venta rivers with expectation of the wild stock stabilisation.