Effects of eutrophication on fish and fisheries in Finnish lakes: a survey based on random sampling

Abstract

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 km2 (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 was collected by means of a postal questionnaire sent to local fishing authorities and lake owners. The results show that the fish community structure is cyprinid dominated, reflecting eutrophication in 2100 lakes (7% of all the target lakes). Strong fouling of the fishing gear, as well as a great abundance of unwanted species in the catch of passive gears, were considered to be a continuous problem in more than 10% of the lakes. Roach, Rutilus rutilus (L.), and bream, Abramis brama (L.), were the most common species to have increased in abundance in the study lakes, whereas burbot, Lota lota (L.), and vendace, Coregonus albula (L.), decreased, especially in highly eutrophic lakes. High total phosphorus and cyprinid dominance in lakes were found mainly in the most intensive agricultural regions in the western and southern parts of Finland.

Analysis of artisanal fisheries in two reservoirs of the upper Paraná River basin (Southeastern Brazil)

“…On the other hand, fish in the Jurumirim Reservoir region is sold in cities near the reservoir, where the supply of fish is low and, consequently, the price increases. With respect to environmental issues, in Finland, for example, eutrophic lakes are generally associated with a devaluation of fish prices and exotic species also have a low market value (Tammi et al, 1999). A similar finding was reported in northeast Brazil (Attayde et al, 2011).…”

“…a For details on the use of capture techniques, see Novaes & Carvalho (2009, 2011 (De Silva et al, 2004). A number of research projects have indicated that, in Brazil and in other countries, the fish catch has shown declines several years after the introduction of such species (Tammi et al, 1999;ECO -AES Tietê, 2001;Wolos et al, 2009;Attayde et al, 2011;Han & Dumont 2011). The negative impacts of species introductions on native species, as well as the association between the tilapia and eutrophication, has been demonstrated in many studies (including Starling et al, 2002;Figueredo & Giani, 2005;Attayde et al, 2007).…”

The relationship between species richness and taxonomic distinctness in freshwater organisms

“…This pattern was also strongly related to environmental gradients, with species richness increasing with lake size and conductivity, whereas taxonomic distinctness was related to factors portraying lake productivity and perhaps was also associated with an increase in habitat heterogeneity in terms of increasing macrophyte cover and diversity from oligotrophic to mesoeutrophic conditions (Rørslett 1991). As high-productivity lakes in boreal and temperate regions are typically dominated by cyprinids (e.g., Tammi et al 1999;Jeppesen et al 2000), instead of species divided equally among several families and orders, productivity may actually decrease taxonomic distinctness, while species richness may either increase or remain unchanged with productivity compared to lower productivity conditions. The pattern was rather different in the other species-poor fish data set, however; in fact, an opposite pattern was found for one data set of stream diatoms, in which species richness and taxonomic distinctness were positively related.…”

Landscape factors influencing lake phosphorus concentrations across Minnesota

“…Decreases in hypolimnetic oxygen concentrations have direct negative effects on fish that physiologically require oxygenated cold water to survive, grow, and reproduce. Cultural eutrophication has caused declines in many European and North American coldwater fish populations (Hasler 1947, Tammi et al 1999. Latta (1995) reported that cisco (Coregonus artedii) have been extirpated in at least 14% of Michigan lakes, primarily from eutrophication.…”