FISHERY OF LAKE-LADOGA - PAST, PRESENT AND FUTURE

The post-war fishery of Lake Ladoga can be divided according to its ca tch level into four periods. In the years 1945-1954 the total annual c atch increased, and reached the level of 4000 tonnes. In this period t he fish stocks that had increased during the war years were intensivel y exploited. However, this fishery was not in balance with the stocks during the period 1955-1963. As a consequence, the catch decreased dra stically, being sometimes less than 2000 tonnes.Controlling the fisher y restored the abundance of whitefish Coregonus lavaretus (L.) and zan der Stizostedion lucioperca (L.). This increased the total annual catc h to about 5500 tonnes in 1964-1989. However, the fishery control meas ures have not been sufficient to achieve the conservation of salmon Sa lmo salar L. m. sebago, brown trout Salmo trutta L. and the migratory lake whitefish stocks. A decrease in the total fish catch has been obs erved since 1990. This decrease may be related to the deterioration of the environment of Lake Ladoga, caused by anthropogenic factors. The unfavourable state of the ecosystem has led to decline of the whitefis h stocks and, especially during the last few years, to drastical decli ne of zander. Acute problems, to be faced in the near future, are conn ected with the hatchery maintenance of several river-spawning stocks, e.g. salmon, brown trout and migratory whitefish, because the existing fish hatcheries are insufficient in capacity and technically outdated .