An application of a bioenergetics model to Eurasian perch (Perca fluviatilis L.)

A bioenergetics model was developed for Eurasian perch ( Perca fluviatilis L.) by revising an existing model for yellow perch and walleye. Data were gathered from field studies and the literature. Besides adjusting the original parameters of the model, effects of season on consumption and metabolic rates were added. The predictive capability of the revised model was high both concerning the levels of growth and its seasonal development in the Baltic coastal waters to which the model was applied. Perch young-of-the-year attained almost maximum consumption and growth except in the highest temperatures experienced. In larger fish, the model estimated consumption to be about 50 per cent of the maximum possible rate.     

Copper-stimulated respiration in the unfertilized egg of the Eurasian perch, Perca fluviatilis (L)

The addition of Cu2+ (0.1-1.0 mM) to respiring, unfertilized eggs produced a marked stimulation in the rate of respiration whereas Zn2+ had no effect over the same concentration range. In the absence of Cu2+, temperature had little effect on unfertilized egg respiration but the Cu2+ stimulated respiratory rate showed the more normal response with a Q10 of 1.86 (10-20 degrees C). It appears that perch egg respiration is rate-limited by a physical event and it is suggested that Cu2+ may act by dissipating an oxygen permeability barrier located at the chorion.     

Exceptionally big individual perch (Perca fluviatilis L.) and their growth

In Lake Windermere (U.K.) where there was a dense, slow-growing population of perch ( Perca fluviatilis L.) which had an l _x of about 180 mm, there co-existed a few individuals with an l _x of 463 mm. Data from 137 of these big perch, mostly caught in gillnets fishing for Esox lucius L., were examined. Their early growth was identical to that of normal perch, but, at an age, varying between individuals, from 1 to 8 and averaging 4 years, their growth accelerated for about 4 years and then followed a von Bertalanffy model with an l _x of 463 mm. They thus had a 'double' growth-curve that is revealed only if individual growth is examined. Acceleration tended to occur in certain calendar years and was correlated with strong year-classes of young perch. Growth was greater in years with warm summer water temperatures. There were no changes in the growth of big perch, after they had achieved 290 mm, during a period of great changes in the population density and an increase in the growth of normal perch < 290 mm. No more big perch were caught in Windermere between 1967 and 1990. Net selection, length-weight relationships, seasonal cycle in gonad weight, and opercular-body length relationship were the same as those of normal perch. The few available data suggest that big perch were piscivorous, feeding largely on small perch. The distribution of sites in the lake where big perch were caught is contagious, catches follow the negative binomial; but within fishings that caught big perch at the same site and time, catches were more evenly distributed than random. It is postulated that most adults would have accelerated their growth if they had sustained piscivory. Similar big perch have been found in other lakes.     

Distribution of perch (Perca fluviatilis L.) during their first year of life in Lake Constance

The distribution and behaviour of larval and juvenile perch (Perca fluviatilis L.) were studied for two years in large, deep Lake Constance. After hatching larvae were transported by water currents to the open water. The majority of larvae remained in the pelagic zone for about one month. In both years, their return to the littoral zone coincided with the decline of pelagic zooplankton abundance. After returning to the littoral zone, juveniles stayed among submerged macrophytes within 5 m depth and lived apart from larger perch which lived at depths of 6–20 m. By late summer, juveniles changed their distribution pattern: during the day they stayed intensively close to piers and ports, but increased their swimming activity at dusk, cruising among shallow and deep waters and feeding on zooplankton, and rested on the bottom at night. This behaviour appears to be related to the decrease of inshore food resources and to the presence of predators in deeper water. 0⁺ perch left the littoral zone and moved into deep waters when autumnal mixing began in late October. They overwintered near the bottom at depths of more than 30 m. During most of the year, juvenile and adult perch were separated from each other. But as soon as they occupied the same habitat, the occurrence of cannibalism increased.     

Stable isotope variability in tissues of the Eurasian perch Perca fluviatilis

Stable isotope analysis is frequently used as a complementary method of dietary analysis, to describe trophic relationships and assess food-web structure. These studies allow a precise determination, based on the calculation of a diet-tissue fractionation factor. The fractionation factor, determined for whole organisms or specific tissues, may vary substantially in natura. In the present study, delta13C and delta15N were assessed in lipid-free tissues (spleen, liver, viscera, scales, gills, spine, white muscle, brain) and in available energy reserves (proteins, glycogen, lipids) of Eurasian perch (Perca fluviatilis) reared under controlled conditions and fed for 4 months with the same artificial diet. Some discrepancies in delta15N and delta13C data were observed among tissues, respectively up to 3.43 per thousand and 2.54 per thousand for delta15N and delta13C. The 15N signature in organs depends on their metabolic activity. Despite a significant delta13C enrichment from feed to tissues, the lipids in spine, liver and viscera exhibit a certain stability.     

'Pear-shaped' cells in the digestive tract of the perch Perca fluviatilis (L.)

Light and electron microscopy revealed the presence of 'pear-shaped' cells amongst the mucosal cells of the stomach, pyloric curvature, pyloric caeca and the anterior-most region of the intestines of perch. The cells are usually located in the distal region of the mucosa and are approximately half the height of the other mucosal cells. Electron microscopy shows that the cells are composed of thick outer sheaths which are fibrillar in appearance. The cytoplasm is characterized by electron dense rods numbering from three to fifteen, which originate from the supranuclear region of the cells and converge apically. The rest of the cytoplasm is composed of Golgi apparatus, secretory vacuoles, minute mitochondria and a network of cytoplasmic strands laden with ribosomes. The organization of organelles in these cells does not resemble that of other mucosal cells of the alimentary canal. Contrary to what has been suggested previously, the 'pear-shaped' cells neither resemble nor represent stages in the formation and maturation of goblet cells.     

Complexity of lectins from the hard roe of perch (Perca fluviatilis L.)

Fish eggs are a rich source of lectins, the sugar-binding (glyco)proteins. In this paper we aim to further characterise perch roe lectins using several protein characterisation techniques including affinity chromatography and protein sequencing. Perch roe lectins are comprised of two subunits, subunit A and subunit B which have molecular weights of 12,400 and 12,000, respectively. These subunits form multiple aggregates A_nB_n in which the two subunits are present in differing ratios and, also as an `homogeneous' aggregates of one of the subunits A_n or B_n. Lectins A_n (designated A thereafter) and lectin B_n (designated B thereafter) formed by one type of subunit only (subunit A or B) were isolated in a pure state. Lectin B could also be isolated by spontaneous precipitation occurring during incubation of the perch roe extract at 4°C. Lectin B has a higher affinity for d-glucose than lectin A, whereas both lectins (A and B) have a similar affinity for l-fucose. The N-terminal region of subunit B showed the following amino acid sequence: EPAXPPWGTQFG-, whereas the N-terminus of subunit A was blocked and therefore could not be directly sequenced. Differences between subunits A and B were also found in amino acid composition. This unusual complexity and variability of perch roe lectins is likely to have physiological significance which, as yet, remains to be determined.     

Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)

The level of gene flow is an important factor influencing genetic differentiation between populations. Typically, geographic distance is considered to be the major factor limiting dispersal and should thus only influence the degree of genetic divergence at larger spatial scales. However, recent studies have revealed the possibility for small-scale genetic differentiation, suggesting that the spatial scale considered is pivotal for finding patterns of isolation by distance. To address this question, genetic and morphological differentiation were studied at two spatial scales (range 2–13 km and range 300 m to 2 km) in the perch ( Perca fluviatilis L.) from the east coast archipelago of Sweden, using seven microsatellite loci and geometric morphometrics. We found highly significant genetic differentiation between sampled locations at both scales. At the larger spatial scale, the distance per se was not affecting the level of divergence. At the small scale, however, we found subtle patterns of isolation by distance. In addition, we also found morphological divergence between locations, congruent with a spatial separation at a microgeographic scale, most likely due to phenotypic plasticity. The present study highlights the importance of geographical scale and indicates that there might be a disparity between the dispersal capacity of a species and the actual movement of genes. Thus, how we view the environment and possible barriers to dispersal might have great implications for our ability to fully understand the evolution of genetic differentiation, local adaptation, and, in the end, speciation.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 746–758.     

Local growth differences in perch (Perca fluviatilis L.) in a Baltic archipelago

Data on the chemical composition of the hard water rivers Rhine and Rhone, published elsewhere, are stored in a new data bank, RRQUE. In this paper the seasonal variation in pH and concentrations of calcium, bicarbonate and sulphate at 7 stations in the Rhine and 7 in the Rhone are described. The concentrations of calcium, bicarbonate and sulphate show important increases with increasing distance from the source. In both rivers acidification gradually occurs downstream and is thought to be caused by the decomposition of disposed organic matter. It is shown that the normal seasonal patterns of these 4 chemical variables are negated by anthropogenic effects.     

The age and growth of perch (Perca fluviatilis L.) in two Scottish lochs

This study is concerned with the age and growth of perch ( Perca fluviatilis L. ) in two contrasting Scottish lochs-the Dubh Lochan and Loch Lomond. Age and back-calculated growth were determined from annual rings in the opercular bones, and during the 2-year project 470 perch from the Dubh Lochan and 796 from Loch Lomond were examined. Growth in length in the two lochs, though similar for the first 2 years, differed thereafter, the average length at 8 years in the Dubh Lochan being less than 15 cm, that in Loch Lomond more than 23 cm at the same age. In neither locality did the growth of perch follow the Von Bertalanffy growth formula. Reasons for differential growth rates are discussed and comparisons made with the growth of perch in other waters in Europe and North America.     

Differences in growth of perch (Perca fluviatilis L.) in two small forest lakes

Growth patterns and food composition of perch, Perca fluviatilis L., was studied in two small forest lake populations in southern Finland. Size and morphometry of the lakes and physical and chemical properties of water are similar. There is a clear difference in the growth rates of perch between the two lakes. The difference in growth is highly significant in all age groups. In the first lake there is a perch population of 2 000 (1750 ind · ha^–1) adult fishes. In the second lake there is a small population of pike, that keeps the perch population down: 200 adult perch (530 ind · ha^-1). The main food items of perch are crustacean zooplankton, Asellus aquaticus L. and Trichoptera larvae in the first lake and zooplankton, Odonata larvae, Ephemeroptera larvae and Heteroptera in the second.It is concluded that the main reason for the growth difference of studied perch populations is the different population density. There are also differences in species composition of bottom fauna of the lakes, maybe owing to the floating Sphagnum peat moss vegetation in the second lake. This can also affect the growth difference between the two populations of perch.     

Ultrastructure of muscle fibres in head and axial muscles of the perch (Perca fluviatilis L.)

Summary White, pink, red and deep red fibres, selected from a head muscle and from axial muscles of the perch, show significant differences in actin filament length, Z line thickness, Z line lattice space, myofibril girth, the percentages volume occupied by T system and terminal cisternae of the SR, and in the degree of T system SR contact per sarcomere. In both muscles the degree of T system SR contact decreases in the order: white, pink, red, deep red, which suggests a decrease of contraction velocity in the same order.The position of the T system (at the Z line or at the AI junction) is related to the actin filament length. The actin filaments in the red fibres are appreciably longer than in the white, which suggests that the sarcomeres of the red fibres have a broader length-tension curve. The Z line thickness is positively correlated with the actin filament length and, in the white and the red fibres, negatively with the degree of sarcomere shortening. Thicker Z lines are suggested to allow greater sarcomere sizes (length or girth).The percentage volume occupied by mitochondria varies independently of the extent of membrane systems.The ultrastructural characteristics of the fibre types are in agreement with the functional roles as reported in literature.     

Fecundity and reproduction of perch (Perca fluviatilis L.) in Lake Agios Vasilios, Greece

SUMMARY. In Lake Agios Vasilios, male perch become sexually mature during their first year of life whereas females become sexually mature during their second year. The mean absolute fecundity was 8080 eggs; values ranged from 2080 to 28488. The mean relative fecundity was 141 eggs/g body wet weight (ranging from 113 to 201). The absolute increase in weight of gonads is related to the age of the fish. The spawning period is from the middle of March to the beginning of April, at a mean water temperature of 8°C.     

Postglacial colonization shows evidence for sympatric population splitting of Eurasian perch (Perca fluviatilis L) in Lake Constance

Previous microsatellite analysis showed that two subpopulations of perch (Perca fluviatilis L) exist in Lake Constance. This raises questions of whether (i). Lake Constance was colonized by two populations that diverged in allopatry, or (ii). the two subpopulations diverged in sympatry. Sequence analysis of a 365 bp mtDNA fragment (5'-end of the D-loop) of perch from Lake Constance and adjacent waters revealed 10 haplotypes. We suggest colonization via the Danube river, based on the frequency and dispersion of haplotypes, and knowledge of the lake's palaeohydrological development. Pairwise FST-values using mitochondrial DNA sequences showed no significant population subdivision. Our study provides strong evidence that subpopulations of perch in Lake Constance have diverged in sympatry.     

A contribution to the knowledge of the stunted growth of perch (Perca fluviatilis L.) in Holland

Summary The stunted growth of the Dutch perch was studied. To calculate the age and former growth the winterrings of the scales were used. The excellent growth of perch in some parts of Holland in contrast to the bad growth reported by foreign authors is discussed. It is pointed out that the latter growth may be ascribed to the existence of false winterrings, from which one can get rid by dipping the scales in a HCl-solution.It appeared that the initial growth of the stunted perch up to about 13 cm is good. The stunted growth afterwards must be ascribed to a shortage of prey-fish. Especially the smelt seems to be very important. As, however, in Holland young roach are abundant it seems incomprehensible why these cannot serve for suitable perch-food. To investigate this problem the conduct of hunting perch was studied in an aquarium.The results of the aquarium-experiments were in agreement with the change in food-diet at a certain length discussed by other authors; also with the assumption that middle-sized perch do not prey upon smaller congeners.Concerning the preying upon roach it became clear that a single perch will scarcely or not succeed in seizing a roach. The hunting is accomplished by cooperation in open water stretches. Amidst plants perch does not hunt. Hence the stunted growth of perch in Holland must be ascribed to the many plants in Dutch waters, between which the roach may easily escape hunting by perch.A short comparison of prey-sizing by wels, pike pike-perch and perch is made.     

Sex steroid dynamics during embryogenesis and sexual differentiation in Eurasian perch, Perca fluviatilis

It is widely accepted that sex steroid hormones play an important and a specific role during the process of sex differentiation in fish. In order to describe the role of the three main sex steroid hormones (testosterone--T, 17beta-estradiol--E2 and 11keto-testosterone--11KT) during embryogenesis and sex differentiation in Eurasian perch, Perca fluviatilis, eggs, larvae and juveniles originating from two mixed-sex and two all-female progenies were regularly sampled from fertilization to hatching (D0) and from hatching to day 70 post-hatching (D70). Just after spawning, a significant amount of sex steroids [T (1634.2pgg(-1)), E2 (554.4pgg(-1)) and 11KT (1513.2pgg(-1))] was measured in non-fertilised eggs suggesting a maternal transmission of these steroids. From D2 to D70 post-hatching, E2 levels were significantly higher in mixed-sex progenies (median: 725.7pgg(-1)) than in all-female progenies (156.2pgg(-1)) and significantly increased after the onset of the histological differentiation of the gonad in both progenies (D35). Levels of 11KT were significantly higher in mixed-sex (median: 431.5pgg(-1)) than in all-female progenies (below the limit of assay detection) and significantly increased at D35 in all-female progenies (median value: 343.2pgg(-1)). Mean 11KT to E2 ratio was six-fold higher in mixed-sex progenies (1.35) than in all-female progenies (0.24). The data suggest that the 11-oxygenated androgen (11KT) plays a major role in the male differentiation process, and that sex differentiation in Eurasian perch is probably determined by the 11KT to E2 ratio.     

Population structure,growth and fecundity of perch (Perca fluviatilis L.) in an acidified river system in Southern Norway

Population structure, density and reproductive potential of perch (Perca fluviatilis L.) from 4 acidified lakes in a river system in Southern Norway were investigated. The upper 3 lakes were most affected by acidification and the number of perch caught per unit effort indicate three-fold increase in density from the upper Gjerstadvann to the lower Brøbørvann. Low density of perch in the upper lakes is explained by; 1) Abnormal mortality occurring in episodes due to acidification, probably caused by aluminium toxicity at pH = 5.2–5.4. 2). Acid water (pH ≤ 5.0) during spawning and development of eggs and larvae, resulting in recruitment failure. Juvenile mortality of perch may depend on the density of the parental stock. In the 3 upper lakes, the density of adult perch probably was too low to produce significant juvenile mortality, and in these lakes the recruitment probably depended more on the May water quality. Improved water quality increases egg hatching and survival and also benefits zooplankton production, the main food for perch during the first summer. Low population density has reduced competition for food and thus improved growth of perch in the 3 upper lakes compared to the lower lake. The perch in Brøbørvann mature at higher age and have lower individual fecundity than perch in Gjerstadvann, an effect of both slower growth and lower length specific fecundity in Brøbørvann. In Gjerstadvann, the perch therefore have a higher reproductive potential relative to the stock density, and may, when the water quality is good enough, give rise to strong year-classes and more frequent year-class fluctuations than perch in the less acid Brøbørvann.     

Feeding range of age 1+ year Eurasian perch Perca fluviatilis in the Baltic Sea

Using the widespread Eurasian perch Perca fluviatilis as a model organism, feeding ranges were investigated using stable‐isotope ratios (δ¹⁵N and δ¹³C) and body condition. Differences were found between closely located sampling sites in a littoral area without obvious migration barriers, indicating that individual fish had small feeding ranges. Body condition differences between sampled stations were consistent over 4 years. Such sedentary behaviour is important to consider in, e.g. fisheries management and environmental monitoring, as local catch regulations may be meaningful or geographic stability in sampling locations may reduce noise in data.