Fluctuations of perch populations in Lake Geneva from 1984 to 2011 estimated from the number and size of egg strands collected in two locations exposed to different fishing practices

Fluctuations in the number and size of spawning perch (Perca fluviatilis) in Lake Geneva were evaluated and compared each year from 1984 to 2011 in two locations. This evaluation was based on: (1) each mature female lays only one egg strand per year and (2) the number and size of mature females are well correlated with those of their egg strands. Egg strands were counted and measured at two locations in France and in Switzerland. The collection of egg strands from either artificial substrates (France) or by direct sampling of the natural lake bottom by a diver (Switzerland) did not seem to affect the results. In most years the number and mean width of egg strands fluctuated in the same way in both locations. In addition, yearly perch catches were correlated with the number of egg strands at both locations. However, more small egg strands were found in France than in Switzerland, whereas the reverse was true of large egg strands. Fishing pressure concentrated to a greater extent on small perch in France than in Switzerland could explain this difference.     

Systemic infection in European perch with thermoadapted virulent Aeromonas salmonicida (Perca fluviatilis)

In non‐salmonid fish, Aeromonas salmonicidacan cause local infections with severe skin ulcerations, known as atypical furunculosis. In this study, we present a systemic infection by a virulent A. salmonicidain European perch (Perca fluviatilis).This infection was diagnosed in a Swiss warm water recirculation aquaculture system. The isolate of A.  salmonicida encodes a type three secretion system (TTSS) most likely located on a plasmid similar to pAsa5/pASvirA, which is known to specify one of the main virulence attributes of the species A. salmonicida. However, the genes specifying the TTSS of the perch isolate show a higher temperature tolerance than strains isolated from cold‐water fish. The function of the TTSS in virulence was verified in a cytotoxicity test using bluegill fry and epithelioma papulosum cyprinid cells.     

Eurasian perch Perca fluviatilis growth and fish community structure,inside and outside a marine‐protected area in the Baltic Sea

Growth of Eurasian perch Perca fluviatilis L. and fish community structure between sites within a marine‐protected area (MPA) and unprotected sites in the Baltic Sea were examined. Von Bertalanffy, logistic and Gompertz growth models were fitted to P. fluviatilis length at age data, and the logistic model was the most parsimonious for growth between locations. A larger mean maximum size (L_∞) and a smaller instantaneous growth rate (g) were found within the MPA. All three models also predicted that after age seven, fish inside the MPA would be larger. Community structure differed with more P. fluviatilis collected outside of the MPA, and more roach Rutilus rutilus (L.) and bleak Alburnus alburnus (L.) collected inside the MPA. These growth differences may be indicative of recreational fishing effects on P. fluviatilis outside of the MPA, a result of complex interspecific and intraspecific species interactions, or other undetected environmental variation between locations.     

Does the consumption of divergent resources influence risk taking behaviour in juvenile perch (Perca fluviatilis L.)?

Heynen M, Heermann L, Borcherding J. Does the consumption of divergent resources influence risk taking behaviour in juvenile perch (Perca fluviatilis L.)?
Ecology of Freshwater Fish 2011: 20: 1–4. © 2010 John Wiley & Sons A/S     

Seasonal and size-related changes in the diet of perch,Perca fluviatilis L., in the shallows of an Australian river,and their implications for the conservation of indigenous teleosts

1. Perca fluviatilis was sampled monthly over 2 years from the shallow waters (<2 m deep) of the Collie River in south-western Australia to determine the diet of this introduced species and the extent to which it comprised indigenous fish species. 2. As P. fluviatilis increased in size, its diet shifted from predominantly planktonic crustaceans to benthic invertebrates, with decapod crustaceans constituting between 55% and 88% of the volume of the food ingested by larger fish (> 120 mm long) in spring, summer and autumn. 3. All size groups of P. fluviatilis fed on the small indigenous teleosts Edelia vittata and Bostockia porosa. 4. The prevalence with which the different size groups of P. fluviatilis ingested indigenous fish species in the main channel of the river was as high as 14% in fish < 50 mm long in summer, 25% in fish 50–120 mm long in spring and 17% of fish > 120 mm long in autumn. 5. Despite appreciable predation and a relatively high prevalence of P. fluviatilis, indigenous fish species have coexisted with perch in the Collie River since the early 1900s. Such coexistence has apparently been facilitated by a high density of invertebrate prey (as a result of eutrophication) and limited interspecific dietary overlap. 6. The absence of E. vittata in those parts of a nearby river system now occupied by P. fluviatilis and the extremely high prevalence of fish that is sometimes found in P. fluviatilis stomachs, suggest that under certain extreme conditions, such as when a marked depletion in alternative food sources occurs, the presence of perch could pose a threat to the conservation of indigenous fish species in certain river systems in south-western Australia.     

Importance of maternal size on the reproductive success of perch,Perca fluviatilis,in small forest lakes: implications for fisheries management

Abstract 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 bigger eggs that had higher hatching percentage resulting in considerably higher fry production. Larvae of large females were heavier and survived longer with bare yolk sac reserves. The relation between egg dry weight and female length differed between the study lakes suggesting varying maternal influence in different environments. Decrease in the share of large individuals in a perch population can substantially reduce the amount and quality of larvae produced. The results can be applied to improve the sustainability of perch fisheries.     

Composition of the microbial communities in the gastrointestinal tract of perch (Perca fluviatilis L. 1758) and cestodes parasitizing the perch digestive tract

Using the approach of sequencing the V3-V4 region of the 16S rRNA gene, we have analysed the bacterial diversity associated with the distinct compartments of the gastrointestinal tract of perch (Perca fluviatilis) and cestodes (Proteocephalus sp.) parasitizing their digestive tract. The dominant microbiota associated with cestodes (Proteocephalus sp.) was represented by bacteria from the genera Serratia, Pseudomonas and Mycoplasma. By comparing the associated microbiota of perch and cestodes, a clear difference in bacterial composition and diversity was revealed between the community from the stomach content and other parts of the gastrointestinal tract of fish. Microbiota associated with cestodes was not significantly different in comparison with microbiota of different subcompartments of perch (mucosa and content of intestine and pyloric caeca) (ADONIS, p > .05) excluding microbiota of stomach content (ADONIS, p ≤ .05). PICRUSt-based functional assessments of the microbial communities of perch and cestodes indicated that they mainly linked in terms of metabolism and environmental information processing and could play an important role in the nutrition and health of host.     

Splenic lipidosis in intensively cultured perch,Perca fluviatilis L.

Macroscopically visible lipid deposition varying in size from pinpoint to 8‐mm diameter was found in spleens of a population of intensively farmed perch, Perca fluviatilis L. over a 24‐month rearing period. Large agglomerates of adipocytes distinguishable from surrounding normal tissue occurred in all individuals with spleen lipidosis. Several affected fish presented total dystrophy of large clusters of hepatocytes. Prevalence of lipidosis was 5.0% at 12 months and 16.6% at 24 months. There was no significant difference between fatty acid profiles of liver or perivisceral fat of perch with and without lipidosis except for linoleic, myristic, γ‐linoleic, cis‐eicosatrienic, palmitooleic acid. Body weight and hepatosomatic, perivisceral fat and splenosomatic indices were not associated with lipidosis. There was no significant effect of lipidosis on mortality or growth.     

Year class variation in fluctuating asymmetry in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake

Fluctuating asymmetry is the random deviation from perfect bilateral symmetry owing to developmental perturbation, proposed as an indicator of sublethal environmental effects. This was measured in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake. Eleven paired meristic and morphometric characters were scored for fluctuating asymmetry. Level of fluctuating asymmetry differed significantly between year classes for two of the meristic characters, lower extra gill rakers and upper extra gill rakers, and also for an index summarizing number of asymmetric meristic characters per individual. This year class variation in fluctuating asymmetry is probably due to large variation in water quality during early development of perch embryos in spring. For future work on fluctuating asymmetry on fish we recommend the use of as many year classes as possible in the analyses.     

Involvement of sex steroids in final stages of oogenesis in Eurasian perch, Perca fluviatilis

Significant plasma 17,20β-dihydroxy-4-pregnen-3-one peaks were measured for the first time in female Eurasian perch, Perca fluviatilis, during the pre-ovulatory period, reaching 3.5 ng ml^?1, but was not synchronized with final maturation and ovulation stages.     

Early development and allometric growth in hatchery‐reared Eurasian perch,Perca fluviatilis L.

The morphological development and allometric growth patterns of Eurasian perch, Perca fluviatilis L., a highly valued commercial species, were studied under intensive rearing conditions from hatching up to 50 DPH (Days Post Hatch). Based on the external morphology, four different phases during early development of Eurasian perch were identified: pre‐flexion larva 0–20 DPH (5.70–10.16 mm TL); flexion larva 22–30 DPH (11.09–15.14 mm TL) and post‐flexion larva/juvenile 32–50 DPH (18.00–24.75 mm TL). The results indicate that growth period when final replacement of all temporary (larval) structures and most important changes in the shape of P. fluviatilis occurred (between 13.95 and 24.06 mm TL, during flexion and post‐flexion phase) can be considered as a transitional period between the larva and juvenile. All body segments, except trunk length and tail length showed fast growth (positive allometry) throughout the entire studied period or up to the respective inflexion point with a common tendency to isometry. In addition, the specific behaviours (e.g. pelagic way of life) of Eurasian perch larvae resulted in some characteristic allometric growth patterns in the posterior region, different from the majority of other teleosts. The results are discussed with respect to the ontogeny of the functional morphology under both ecological and aquaculture considerations.     

Influence of photoperiod regimes on the Eurasian perch gonadogenesis and spawning

The effects of photoperiod regimes under ambient temperature on gonadal growth and spawning were investigated in Eurasian perch, Perca fluviatilis. This study showed that continuous lighting inhibited reproduction in male and female fish with very low sex steroid levels being measured. Constant LD 16:8 resulted in heterogeneous gonad development and sex steroid levels compared to natural regime, with only 54% of females and <?30% of males maturing. Seasonal variations in daylength also seem to be required to control reproduction.     

Habitat partitioning among three predatory fish in a temperate reservoir

The diversity of predatory species plays a key role in ecosystem functioning but our understanding of the mechanisms underlying their coexistence is limited, particularly in freshwater ecosystems. Northern pike Esox lucius, European perch Perca fluviatilis and pikeperch Sander lucioperca are three widespread predatory species in European lakes, where they often coexist. As potential competitors, we hypothesised that partitioning habitat is a determinant of species coexistence. This was tested by quantifying the variability of their habitat use in tracking adult individuals in the Bariousses reservoir (France, 86.6 ha, mean depth 7.1 m). Specifically, we investigated their distribution along the littoral–pelagic and depth axes along the daily cycle and across seasons. From littoral to pelagic waters were first found pike, then perch and finally pikeperch. Pike was the closest to the surface while pikeperch was the deepest. This general pattern was, however, variable across seasons with the three species located in the upper layer in summer during reservoir stratification. Individuals were more evenly distributed along the littoral–pelagic axis and closer to the bottom when water was mixing (autumn, winter). In summer, perch used more intensively in the pelagic zone during the daytime. Other species did not show any diel change of habitats. Our results highlighted that species coexistence is associated with habitat partitioning among these three predators, with perch showing a more variable behaviour regarding habitat characteristics. Now more than ever, in the context of global change which modifies habitats, it is of crucial importance to understand the coexistence mechanisms of species that shape ecosystems.     

The effect of depth on the interaction between perch (Perca fluviatilis) and minnow (Phoxinus phoxinus)

We tested the hypothesis that small fishes avoid piscivores by increasing their use of shallow water areas, thereby reducing the capture success of the piscivore. Experiments were conducted in 600-1 aquaria, using perch (Perca fluviatilis) as the piscivore and minnow (Phoxinus phoxinus) as the prey. Two size classes of minnows, presented alone and together, were placed together with perch in aquaria with and without shallow water areas. The capture success of perch and use of depth by minnows changed as predicted by our hypothesis. In addition, we observed a decrease in the shoal size of minnows when perch were present. Perch selected large minnows over small minnows when both size classes were present, probably because large minnows were a more energetically profitable prey size.     

Ice fishing reveals size structure but not abundance of Eurasian perch in small boreal lakes

Management of inland recreational fisheries would benefit from stock abundance and size structure data. Feasibly standardised angling methods such as ice fishing could produce representative catch-per-unit-effort (CPUE) information on the abundance of different-sized fish in small lakes. Here, we first used standard Nordic multimesh gillnets to obtain number-per-unit-effort (NPUE), biomass-per-unit-effort (BPUE) and size structure data on Eurasian perch (Perca fluviatilis) stocks in 11 small boreal lakes in summer. Second, the same lakes were ice-fished by voluntary anglers using a pre-defined, loosely standardised protocol to obtain angling-based NPUE, BPUE, and length frequency distributions. Effects of environmental variables such as water oxygen concentration and light penetration on angling catch rates were controlled statistically. Neither perch Nordic gillnet NPUE nor BPUE corresponded to ice-fishing CPUEs. However, the length distribution of the catch did not differ between methods. Our results imply that traditional ice fishing applying natural baits is relatively unselective for fish size and could produce valid length-based indicators for management purposes while angling CPUE was poorly related to Nordic gillnet CPUE.     

The energy requirements of Eurasian perch (Perca fluviatilis L.) in intensive culture

Fish feed constitutes one of the largest costs in aquaculture, therefore inefficient feed management will have a negative impact on fish farm economics. Eurasian perch (Perca fluviatilis L.) is a relatively new candidate for freshwater aquaculture, however little is known about the energy requirements of this species. The aim of this study was to develop an energy requirement model for intensive culture of Eurasian perch reared at rational temperatures. Data on growth (the thermal unit growth coefficient, TGC, ³√g · (°C · days)^?1) and digestible energy need (DEN, kJ DE · g^?1) of Eurasian perch at a size range of 20–180 g and at temperatures of 17–23 °C were used. Regression analysis revealed that both TGC and DEN were affected significantly by fish size (P < 0.001) but not by temperature (P > 0.05). Two models including body size of the fish were developed: (i) an inverse TGC model for evaluation of the daily theoretical weight increment (TWi, g · day^?1) and (ii) a linear DEN model. The TGC model was validated by comparing theoretical data with data obtained from a commercial growth trial. By combining the TWi and the DEN, a model describing the daily theoretical energy requirement (TER, kJ · day^?1) at different temperatures and for Eurasian perch of different sizes was successfully developed.     

Induced spawning in perch, Perca fluviatilis L. using carp pituitary extract and HCG

Induced spawning in Eurasian perch, Perca fluviatilis L., was studied using human chorionic gonadotrophs (hCG) or acetone-dried common carp pituitary with or without hCG. The dose administered to fish was 5700 IU hCG kg^-1 or 4.0 mg kg^-1 carp pituitary with or without 500-700 IU hCG kg^-1 for females and 2850 IU hCG kg^-1 or 2.0 mg kg^-1 carp pituitary with or without 250-350 IU hCG kg^-1 for males. There were no statistically significant differences in quantity of milt in treated and control groups, although the best result was observed when males were treated with a triple injection of hCG and carp pituitary extract. Male spermiating success, expressed as a quantity of milt, was negatively correlated with fish weight. All females treated in this experiment had oocytes at the same division, so time of ovulation was highly synchronous. Spawning success, expressed as a spawning effectivity coefficient (S_c), was highest in fish treated with the triple injection. Spawning methods described in this paper were successful, even though hormones from another order of fish were used.     

Effects of dietary fat levels on growth, feed efficiency and biochemical compositions of Eurasian perch Perca fluviatilis

A feeding experiment was conducted for 10 weeks with Eurasian perchPerca fluviatilis juveniles (33.1–35.9ginitial body weight) using three dietary fat levels (11.7, 15 and 19.3%). Theresults showed that increasing dietary fat content increased growth, feedefficiency and protein utilization of perch (P < 0.05) but did not affectmortality. Lipid analysis showed that the composition of some perch tissueswerealso significantly affected by increasing dietary fat content, with an increaseof lipid deposition in the viscera (from 64.9% in fish fed 11.7 % fat to 78.8%in fish fed 19.3% fat) and liver (from 12.4 to 23.8%) (P < 0.05), while themuscle composition was not affected by the dietary treament. Highdocosahexaenoic acid (22:6n-3, DHA) and high docosahexaenoicacid/eicosapentoenoic acid (20:5n-3, EPA) ratios were found in the liver andmuscle lipids as compared to the dietary fatty acid compositions, suggestingthat Eurasian perch might possess a high capability of converting the longchainhighly unsaturated fatty acids, especially DHA from its dietary precursors.     

Induced spawning in perch, Perca fluviatilis L., using FSH + LH with pimozide or metoclopramide

Induced spawning in perch, Perca fluviatilis L., was studied using follicle stimulating hormone and lutenizing hormone (FSH + LH) with the addition of pimozide or metoclopramide. The doses administered to fish were: 75 IU kg^?1 of FSH + LH with 5 or 10mgkg^?1 of pimozide (P) or metoclopramide (M) in females, and 25 IU kg^?1 of FSH + LH with 2.5 or 5 mg kg^?1 of P or M in males. Hormonal injections in males (except the injection of FSH + LH with 10 mg kg^?1 of M) did not influence the quantity of milt obtained. All females treated in this experiment had oocytes at the same stage of nucleus migration, so the time of ovulation was very synchronous, i.e. 16-24 h after injection. The relationship between the quality of the eggs, expressed as a survival to eyed-egg stage, and latency was inverse. Spawning success, expressed as a spawning effectiveness coefficient (S_e), was highest in the fish that had been treated with FSH + LH with a higher dose of M.     

Development of some digestive enzymes in Eurasian perch larvae Perca fluviatilis

The activities of some digestive enzymes were investigated in Eurasian perch Perca fluviatilis larvae fed live preys during the first month of life. Activities of pancreatic and intestinal enzymes displayed a pattern characteristic of developing animals. Pancreatic enzymes were efficient at the time of hatching. Trypsin and amylase specific activities increased during the first developmental days, then decreased even though segmental activities increased continuously as the larvae grew. The increase of chymotrypsin specific activity was proportional to fish growth. From day 21 after hatching to the end of experiment, the strong increase in the activities of alkaline phosphatase, leucine-aminopeptidase N, maltase and γ-glutamyl transpeptidase reflected the development of brush border membranes of enterocytes. This phenomenon occurred concurrently with a decrease in a cytosolic enzyme, the leucine-alanine peptidase. These opposite patterns indicate a maturation of enterocytes and the acquisition of an adult mode of digestion within the first month of live. This revised version was published online in August 2006 with corrections to the Cover Date.