Rapport nr 137: Provfiske i Långsjön, Östra Kyrksundet, Västra Kyrksundet, Dalkarby träsk och Lavsböle träsk 2013
GREN, M (2013)
GREN, M
Åbo Akademi, Husö biologiska station
2013
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This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-12-2999-2
https://urn.fi/URN:ISBN:978-952-12-2999-2
Tiivistelmä
The lakes Långsjön, Östra Kyrksundet, Västra Kyrksundet, Dalkarby Träsk and Lavsböle Träsk in the Åland Islands were monitored for fish in order to follow up the development of the fish stocks and to classify the lakes according to the EU Water Framework Directive. Fishing nets were put out in the lakes in the summer of 2013 to sample data of fish species, number, size and biomass of fish. Lakes Långsjön, Östra Kyrksundet, Västra Kyrksundet had large standing stocks of fish while Lake Lavsböle Träsk had a small fish stock. The proportion of cyprinids had increased from the earlier fish inventories in lakes Långsjön, Östra Kyrksundet and Västra Kyrksundet. Lakes Dalkarby Träsk and Lavsböle Träsk, which had not been test-fished before, had a high biomass of cyprinids and a small proportion of predatory fish. All the studied lakes were eutrophicated to some extent. Depth and vegetation maps were made for lakes Dalkarby Träsk and Lavsböle Träsk. Together with the lakes’ other classified variables, including physiochemical parameters and chlorophyll a, Lake Långsjön was classified as poor, lakes Östra Kyrksundet, Dalkarby träsk and Lavsböle träsk were classified as good while Lake Västra Kyrksundet achieved a high status. To improve the lakes’ fish stocks I recommend that net fishing in order to remove excess of fish should be carried out in lakes Långsjön, Östra Kyrksundet, Västra Kyrksundet and Dalkarby träsk and measures to increase biomass of predatory fish should be taken in Lake Lavsböle Träsk. For continued monitoring of lakes on Åland I recommend that test fishing should be performed according to a standard protocol.