Search results for "perch"
showing 10 items of 1084 documents
Upstream migration activity of cyprinids and percids in a channel, monitored by a horizontal split-beam echosounder
2003
A 200 kHz digital echosounder (HTI) with two split-beam transducers was aimed horizontally to monitor the upstream migration activity of fish, from 24 April to 28 June, in Aijalansalmi channel (mean width 35 m, length 700 m, and maximum depth 5 m) from large mesotrophic Lake Paijanne to small eutrophic Lake Jyvasjarvi. This study was part of a larger project which aims to analyse the movement of commercially unimportant fish species and reduce the abundance of these fish in L. Jyvasjarvi. Catch samples were collected with a trap net located immediately upstream from the acoustic beams. The most common species in the catch were roach (Rutilus rutilus), perch (Perca fluviatilis), bream (Abram…
Do macrophage centres in freshwater fishes reflect the differences in water quality?
1996
Abstract Macrophage centres have been considered as a potentially useful indicator of fish health. In this histological work we tested this hypothesis with macrophage centres (MCs) in the spleen, the liver and the hematopoietic part of the kidney of two common freshwater fish species in Finland, perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ). Samples were collected over 5 seasons from a system of 4 lakes providing a gradation in water quality. The mean number of MCs/mm 2 and the area covered (μm 2 /mm 2 ) by them differed between individual fish, species, organs, and lakes, with interactions amongst these factors. Hemosiderosis was recorded from the spleen and liver of both fish …
Studies on bucephalid digeneans parasitising molluscs and fishes in Finland I. Ecological data and experimental studies
1991
Two types of bucephalid cercariae are reported from the bivalve Anodonta anatina in two Finnish lakes. One, Type A, resembles in gross morphology the cercaria of Bucephalus polymorphus, and the other, Type B, resembles the cercaria of Rhipidocotyle campanula. Type A daughter-sporocysts develop more slowly, have a greater cercarial productivity and exhibit a differential diurnal rhythm to that of Type B. Cercariae of Type A have a shorter longevity than Type B and tend to encyst in the fins rather than the gill-arches of fish intermediate hosts. The main definitive host of Type A is pike Esox lucius and, in the case of Type B, perch Perca fluviatilis. Adults of Types A and B are morphologica…
Acid stress in respect to calcium and magnesium concentrations in the plasma of perch during maturation and spawning
1988
Plasma calcium and magnesium concentrations in perch,Perca fluviatilis, were monitored in an acid lake, Lake Iso Tenhetty (pH ∼5, Al concentrations 0.3–0.5 mg l-1) compared with a nearby reference lake, Lake Paijanne, in Southern Finland. The effect of acid stress could be noticed as 1/3 lower fecundity of perch in the acid lake. Plasma Ca concentrations were temporarily lower in the middle of the winter in the fish of the acid lake, and in April–May samples the situation was opposite. Plasma Mg concentration was also lower in the perch from the acid lake in midwinter months, when compared with the double as high values (∼3 mmol l-1) from the reference lake. Elevated level of plasma Mg have…
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…
Diet and prey size spectrum of pikeperch in lakes in central Finland
2004
The stomach content of pikeperch Sander lucioperca was studied in 24 lakes in central Finland. The most important prey species was smelt Osmerus eperlanus then perch Perca fluviatilis. The proportion of cyprinids as prey increased with pikeperch total length (LT) and lake phosphorus content. Prey L T and pikeperch L T correlated positively, but the prey-to-predator size ratio correlated negatively with pikeperch L T .
Chernobyl-derived radiocaesium in fish as dependent on water quality and lake morphometry
1995
137Cs concentrations in perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus obtained from lakes of different size and water quality in an area which received about 10–67 kBq m−2137Cs, were compared with environmental data. Radiocaesium concentrations were highest in pike, and were about two to three times higher in the pike and perch than in the roach. The largest perch had about four times more 137Cs than the smallest ones, but the activities in the pike and roach were independent of fish size. All of the water quality parameters examined correlated with 137Cs concentrations in the fish, but the concentrations of 137Cs in the bottom sediment did not. l37Cs fallout and water…
Effects of paper mill effluents on the fish fauna of stony shores of Lake Päijänne
1992
The fish fauna of the stony littoral in the central parts of L. Paijanne was studied by electric fishing on four occasions during 1988–1989. Ten fish species and 1681 individuals (14.5 kg) were caught in the 15 fishing sites (4096 m2) which gives a mean density of 0.41 ind. m-2 and biomass of 3.5 g m-2. Effluent from two large paper mills causes a clear zonation of the fish fauna in the area. In the most polluted shores, only burbot and perch occurred regularly and the reproduction of other species was inhibited. In the semipolluted area (5–15 km from the Kaipola paper mill), burbot and stone loach occurred regularly, but owing to low numbers of perch and bullhead the total densities were u…
The macrophyte, Stratiotes aloides, protects larvae of dragonfly Aeshna viridis against fish predation
2004
Predation could be one force determining which contemporary species occupy a certain habitat. Aeshna viridis is an endangered dragonfly species with a larval distribution strongly associated with lakes where the water plant, water soldier, Stratiotes aloides, occurs. In this study, the larvae were almost exclusively found in patches of S. aloides. To study larval association with S. aloides further, we conducted a series of laboratory experiments. Behavioural experiments indicated that larvae preferred S. aloides. Aeshna viridis larvae were nocturnal and rather inactive. Larvae on S. aloides were less susceptible to predation by the perch, Perca fluviatilis, than larvae on another water pla…
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 …