Fishes and fisheries management in Lake Võrtsjärv

Abstract

L. Võrtsjärv is a large shallow eutrophic pike-perch lake of rather low biological productivity. In the 1950s and 1960s the bulk of the fish caught here consisted of ruffe, young perch and roach. Attempts to reduce the abundance of these undesirable fishes by intensive trawling were unsuccessful. Trawl catch damaged the stocks of commercially important big fishes (first of all, pike-perch), and therefore their numbers became small (except for bream). Subsequently, trawling was stopped, elvers were regularly introduced into the lake and the protection of valuable fishes was improved. As a result of these measures, the total catch of fish decreased temporarily, while the stocks and catches of valuable fishes (above all those of pike-perch and eel) began to grow rapidly. The increasing pressure of predatory fishes (mainly pike-perch and pike) led to a sudden fall in the abundance of less valuable small fish. Recently, fishery has reached an optimum level in the lake. In comparison with the 1950s and 1960s the total catch of fish has now risen more than 1.5 times and the value of the catch as much as 6-8 times (first and foremost on the account of eel).