Deteriorating environmental conditions and overexploitation in situations of insufficient fish stocking or a complete lack of it led to the extinction of salmon in Polish waters. The last population of salmon in the Drawa River disappeared in the mid-1980s. The aim of this work was to re-establish salmon in Polish waters. The salmon for this purpose came from the Daugava River, when in 1985 and 1987, 50 000 and 30 000, eyed salmon eggs were bought, respectively. Up to 1996, salmon spawners were in the floating reared net cages in of the Puck Bay. Since 1994, spawns of salmon have been reared in freshwater at the fish farm "Aquamar" at Miastko. Stocking of smolt started in 1994 and by the year 2001, 2 238 653 one- and two-year-old smolts had been released. Smolts were released into rivers in the Pomeranian region, the Drawa, and the Vistula and its tributaries. Between 1994 and 2000, 77912 one- and two-year-old tagged smolts were released together with untagged ones. The first salmon in the Vistula and Drwęca rivers were noted in 1996. From 1997 to 2000, salmon catches in rivers fluctuated between 413 and 9714 kg. From 1997 salmon spawners were captured for artificial spawning. The largest spawners were 120-cm long and weighed 17.5 kg. Alongside untagged spawners, single tagged salmon were also used for spawning purposes. In 1997, a total of 382 000 eggs were obtained. In later years the number of spawns obtained grew, and in 2000 the number of eggs collected was 2 260 000. In 1996, spawns from salmon raised in pools at Świerzenko were collected. In 2000, there were 1168 females (length 30 - 70 cm) from which 9 300 000 eggs were collected. From 1997, large nests were observed at the spawning grounds in the Drawa River. In next years salmon nests were observed in the Drawa River and also in Parsęta and Wieprza rivers. Percentages of recovers from tagged salmon were very low and varied from zero to 7.35. Tagged salmon migrated all over the Baltic Sea. The most often they were caught in the Gulf of Gdańskarea, near Bornholm Island and in the western part of the Gulf of Finland. Salmon entered rivers mainly into Vistula, Drwęca and Wieprza rivers for spawning purposes. Some spawners strayed and entered rivers to which they were not released as smolt. Higher percentage of homing were observed among smolt into Vistula i Drwęca rivers than among smolt released into Pomeranian rivers. Tagged salmon after the firs year reached average length of 59.4 cm and average weight of 2583 g, after the second year 81.8 and 6255 g, after the third year 102.4 cm and 11800 g respectively.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.