Rapport nr 111: Fisksamhällets sammansättning längs en skärgårdsgradient på NW Åland
JÄRVINEN, M; BORGMÄSTARS, M; WISTBACKA, S (2004)
JÄRVINEN, M
BORGMÄSTARS, M
WISTBACKA, S
Åbo Akademi, Husö biologiska station
2004
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Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:952-12-1341-8
https://urn.fi/URN:ISBN:952-12-1341-8
Tiivistelmä
The structure of fish communities along an archipelago gradient in NW Aland was studied in the summer of 2003 as a follow-up study of earlier studies conducted in 1992 and 1997. Seven locations along the gradient were fished at a depth of 3-5 meters and at five occasions by using fishing nets. The depth gradient ( down to 12-15 meters) was also studied at three of these stations. Hydrography parameters were measured at each fishing occasion. Focus was especial/y placed on pikeperch (Sander lucioperca L.) populations. This species was abundant in the inner and middle archipelago and few individuals were caught in the outer archipelago. It also seems that the pikeperch community has endured we/1 during the last decade.
The results indicate that no big changes in the structure of these fish communities have taken place since the last decade. On the whole, the cold water fish species were dominating in the outer archipelago, wheras the freshwater and warm water fish were dominating in the inner archipelago. The communities in the middle archipelago constituted mainly of a mixture of all these species. lncreasing phosphorous and nitrogen contents and abundance of cyprinids in the inner archipelago indicates eutrophication, which was also the case back in 1992.
The results indicate that no big changes in the structure of these fish communities have taken place since the last decade. On the whole, the cold water fish species were dominating in the outer archipelago, wheras the freshwater and warm water fish were dominating in the inner archipelago. The communities in the middle archipelago constituted mainly of a mixture of all these species. lncreasing phosphorous and nitrogen contents and abundance of cyprinids in the inner archipelago indicates eutrophication, which was also the case back in 1992.