| Summary: | In summer 2002, a study of fish reproduction and aquatic vegetation was conducted in Engrundsfjärden, N Aland. The study area is ta a great extent very shallow and the aquatic vegetation consists mainly of charophytes. The aim af the study was ta investigate how suitable the area is for fish reproduction, what species utilize the area and how the dense charophyte vegetation might effect fish reproduction. The fish assemblage in Engrundsfjärden was dominated by Gymnocephalus cernuus. Perca fluviati/is and Rutilus rutilus. A total af nine species were caught with net fishing. Juvenile fish was sampled with a beach seine and the results showed that reproduction was successful in summer 2002. Cyprinids dominated the seine catches. Six species af charophytes were found in the study area. The dominating species were Chara tomentosa, Chara aspera and Chara canescens. Other charophytes found were Chara fragilis, Chara horrida and Chara baltica. The last two are endangered species in Finland according to the Finnish Environment Centre. Dredging can increase the recruitment area for fish in shallow areas but is a serious threath ta the vegetation, especially charophytes. Dredging increases turbidity by causing resuspension af nutrients and particles from the sediments and thereby reducing fight accessible for plants. Charophyte vegetation is known to form important recruitment, nursery and feeding areas for fish and also for many birds. Plenty af roe and numerous juvenile fish were observed among the charophytes during the study in Engrundsfjärden. Dredging should not be conducted without careful evaluation and consideration of the effects an the charophyte vegetation and the fish assemblage dependent an vegetation in Engrundsfjärden.
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