Search results for "Percidae"
showing 6 items of 16 documents
Visual conditions and habitat shape the coloration of the Eurasian perch (Perca fluviatilis L.): a trade-off between camouflage and communication?
2009
In theory, selection for effective camouflage (i.e. dull coloration) in fish should be strongest when the conditions for visual predation are most favourable, such as in structurally simple pelagic habitats. By contrast, in more sheltered (e.g. littoral) habitats, selection may favour effective intra-specific communication (i.e. bright coloration) (at the expense of crypsis). Poor transparency, as in highly humic waters, should constrain colour adaptations. We investigated phenotypic variation in body coloration of Eurasian perch (Perca fluviatilis L.) in littoral and pelagic habitats of four humic boreal lakes. Perch from the most transparent lake had the lightest and less coloured belly a…
Host searching in Argulus foliaceus L. (Crustacea: Branchiura): the role of vision and selectivity.
1998
In laboratory experiments, the swimming behaviour of the ectoparasite Argulus foliaceus and its infection rates on juvenile perch (Perca fluviatilis) and roach (Rutilus rutilus) were examined. The highest infection rate and a preference for perch juveniles were obtained in darkness, the lowest infection rate and a lack of preference in the light, when aquaria with glass walls (high reflectivity) were used. In the light, when aquaria were lined with black plastic (low reflectivity) an intermediate level of infection for perch and the highest for roach was recorded. Under such conditions roach were significantly more heavily infected than perch; an attack rate 4 times greater was recorded for…
Perch (Perca fluviatilis L.) parasites reflect ecosystem conditions: a comparison of a natural lake and two acidic reservoirs in Finland.
2000
Parasite communities of perch were studied in a natural lake (Vetamajarvi) and two reservoirs (the Kyrkosjarvi and Liikapuro reservoirs) located in Western Finland. All water bodies studied are small, shallow and humic. However, the reservoirs are more acidic than the lake (pH 5.9 and 5.3 vs. 6.4). Altogether, 18 parasite species were found, but the component communities were reduced in the harsh conditions of the reservoirs (12 and six species) as compared with the lake (17 species). In addition, the mean number of metazoan parasite specimens per fish was markedly lower in the reservoirs (64.3 and 14.3 specimens) than in the lake (116.1 specimens). Our prediction on the depauperation of pa…
Concentrations of Organochlorine Substances in Relation to Fish Size and Trophic Position: A Study on Perch (Perca fluviatilis L.)
2000
The aim of this study was to evaluate the importance of trophic position as a determinant of the concentrations of organochlorine substances (OCS) in fish. Perch (Perca fluvatilis) was selected since the species increases in trophic level over the course of its lifetime. The trophic position was characterized by stable isotope analysis of nitrogen and gut content. Perch (130 individuals) of different lengths and of both sexes were analyzed for polychlorinated biphenyls and chlorinated pesticides. There were no pronounced differences in the OCS concentrations between the perch sexes. Perch up to a length of 20 cm did not show any increase in OCS concentrations with increased length, despite …
Reproductive, biochemical, physiological, and population responses in perch (Perca fluviatilisL.) and roach (Rutilus rutilusL.) downstream of two ele…
2001
Perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations in a state of late vitellogenesis were studied downstream of two pulp and paper mills and at upstream references in southern Lake Saimaa, Finland. The mills used elemental chlorine-free bleaching and activated sludge effluent treatment technologies. The exposure of fish to pulp mill effluents, as measured by concentrations of chlorophenolics in the bile and liver ethoxyresorufin-O-deethylase (EROD) activity, was low and almost similar to the references. Nevertheless, bile resin acid concentrations in exposed perch and roach (260-320 micrograms/ml) and bile beta-sitosterol concentrations in exposed roach (1.5-3.5 microgr…
The effect of the length of repeated feed deprivation between single meals on compensatory growth of pikeperch Sander lucioperca
2009
Abstract Juvenile pikeperch ( Sander lucioperca ) were reared for 58 days according to one of the following feeding regimes: control (fed once every day); 1 + 1 (fed every other day); 1 + 3 (one-day feeding followed by a three-day feed deprivation); and 1 + 6 (fed once a week). Control fish had significantly higher growth rate than the 1 + 3 and 1 + 6 fish, and consequently the final weight of the controls (125.2 ± SD 30.0 g, n = 4) was higher than that of the 1 + 3 (84.0 ± 17.9 g) and 1 + 6 fish (64.7 ± 7.2 g). Fish in the treatment groups were capable to compensate for the reduced number of feedings by increasing intake relative to the controls when feed was available. This hyperphagic r…