Population genomics analysis holds great potential for informing conservation of endangered populations. We focused on a controversial case of European whitefish ( Coregonus spp.) populations. The endangered North Sea houting is the only coregonid fish that tolerates oceanic salinities and was previously considered a species ( C. oxyrhinchus ) distinct from European lake whitefish ( C. lavaretus ). However, no firm evidence fo...

Conservation and management of marine biodiversity depends on biomonitoring of marine habitats, but current approaches are resource‐intensive and require different approaches for different organisms. Environmental DNA (eDNA) extracted from water samples is an efficient and versatile approach to detecting aquatic animals. In the ocean, eDNA composition reflects local fauna at fine spatial scales, but little is known about the e...

Abundance, sex ratio and size structure of perch, Perca fluviatilis L., populations were studied in two forest lakes. The influence of maternal size on the amount and quality of eggs and larvae was investigated, and the effect of the spawning stock’s length structure on population egg and fry production was evaluated. The importance of large females was essential for the reproduction of perch. Large perch spawned more and bigg...

The field data from four humic lakes suggested that water colour may have both direct and indirect effects on inter‐ and intra‐specific interactions of perch Perca fluviatilis and roach Rutilus rutilus . The results agree with suggestions that, compared with R. rutilus , P. fluviatilis may be an inferior forager on zooplankton in highly coloured water. As an indirect effect, water colour decreases the coverage of macrophytes a...

In this study of 18 small boreal forest lakes, the effects of abiotic and biotic factors (roach Rutilus rutilus and pike Esox lucius ) on various population variables of perch Perca fluviatilis were examined. As a single variable, the gillnet catch per unit effort (CPUE) of R. rutilus was negatively related to the mean mass of small ( P. fluviatilis . The mean mass of large (≥ 200 mm) P. fluviatilis was the highest at intermed...

The European Union Water Framework Directive stipulates that pressures on surface waters due to diffuse loading of nutrients have to be taken into account in determination of their ecological status. A Finnish data set of fish communities in 178 lakes was used to assess the effects of agriculture‐induced nutrient loads on the ecological status of lakes. The lakes were divided to reference ( n = 100) and impacted sites ( n = 78...

In 36 south Finnish lakes, the number of species, as well as the cyprinids:percids ratio, was dependent, not only on total phosphorus (TP), but also on lake size. Total fish biomass and cyprinid biomass increased along the TP gradient, whereas the dependence of percid biomass was less evident. Perch Perca fluviatilis and roach Rutilus rutilus strongly dominated mesotrophic lakes; in eutrophic lakes the proportion of other cypr...

In the Enonselkä and Laitialanselkä basins of Lake Vesijärvi, perch Perca fluviatilis and roach Rutilus rutilus were abundant in the littoral and in the pelagic zones throughout the summer. In the littoral zone, roach was always more numerous than perch, while perch dominated in the open water. Intraspecific diet overlap values were higher than interspecific values. In the pelagic zone, perch Leptodora kindtii , while small bo...

The effects of eutrophication on fish and fisheries in Finnish lakes were determined by an extensive lake survey conducted in 1995 and 1996. The study lakes (873) were chosen by stratified random sampling from all Finnish lakes with a surface area ≥ 0.04 km 2 (29 515 lakes in all). The chemical parameters of the lake water were determined for water samples taken in autumn 1995. Information on the fish stocks of the study lakes...

Water quality in 16 Finnish lakes did not affect directly densely gill‐rakered whitefish growth, except possibly in an acid (pH 4·9) lake, Iso Lehmaälampi, where acidity may have retarded the growth of whitefish. The density of roach affected whitefish growth in the second year of life: highest growth rates were in lakes without a roach population and lowest growth rates in lakes having strong roach populations. Competition by...