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Objective: The objective of this study was to determine the effects of different social ranking order (SRO) and the enrichments (perch and dust-bath) allocation (EA) on behavior of laying hens in furnished cages.Methods: Total experimental period was 4 weeks. There were 216 Hy-line brown layers beak-trimmed at 1 d of age and selected randomly at 14 weeks of age from a commercial farm, and randomly divided into 36 cages with 6 hens in each cage. High enrichments (perch and dust-bath) allocation (HEA) and low enrichments (perch and dust-bath) allocation (LEA) were provided. Video observations of behavior were obtained from the focal hens between 14 and 18 weeks of age and perching, dust-bathing and other general behaviors of the hens with different social orders were measured.Results: Perching behavior of high SRO hens (HSR) were significantly higher than that of medium SRO hens (MSR), and that of the MSR were significantly higher than that of low SRO hens (LSR) (p0.05). The hens in the high EA cage (HEAC) showed more lying behavior on perch than those in the low EA cage (LEAC) (p0.05), except standing and preening behaviors (p

Interspecific aggression has important fitness consequences across the animal kingdom and can be especially important during species invasions, where asymmetric interactions between native and invasive species can lead to native species declines. We investigated the immediate behavioural consequences of interspecific interactions for a native species, the green anole lizard, Anolis carolinensis, after an invasion by a closely related invasive species, the Cuban brown anole, Anolis sagrei. We housed captive populations of green anoles (6 males, 6 females) in large outdoor enclosures and recorded their display behaviours (displays/min), activity levels (movements/min) and habitat use (2D and 3D home range size, perch height) for 10 days. We then introduced brown anoles and recorded the green anoles' behaviours for another 10 days, seeking differences between pre- and post-invasion behaviours. We recorded behavioural interactions between individuals (i.e. headbob and dewlap displays, chases, mating attempts, fights and copulations) throughout the study. To serve as a density control, we duplicated the experiment in a second enclosure using green anoles as ‘invaders’. We performed the experiment eight times with two densities of invaders: high (4 males, 4 females) and low (2 males, 2 females). We found that green anoles have smaller two-dimensional and three-dimensional home ranges and higher average perch heights after invasions but that these changes resulted from increased population densities rather than aggression from brown anole invaders. Furthermore, although green and brown anoles did display to each other, both species preferentially interacted with conspecifics and escalated aggressive behaviours between the two species (e.g. lock-jawed fights) rarely occurred. Taken together, these findings indicate that high brown anole population densities, rather than direct interference competition, could be driving green anole displacement across the brown anole's invasive range.

The field of stable isotope ecology is moving away from lethal sampling (internal organs and muscle) towards non-lethal sampling (fins, scales and epidermal mucus). Lethally and non-lethally sampled tissues often differ in their stable isotope ratios due to differences in metabolic turnover rate and isotopic routing. If not accounted for when using non-lethal tissues, these differences may result in inaccurate estimates of resource use and trophic position derived from stable isotopes. To address this, the authors tested whether tissue type, season and their interaction influence the carbon and nitrogen stable isotope ratios of fishes and whether estimates of species trophic position and resource use are affected by tissue type, season and their interaction. This study developed linear conversion relationships between two fin types and dorsal muscle, accounting for seasonal variation. The authors focused on three common temperate freshwater fishes: northern pike Esox lucius, yellow perch Perca flavescens and lake whitefish Coregonus clupeaformis. They found that fins were enriched in 13 C and depleted in 15 N compared to muscle in all three species, but the effect of season and the interaction between tissue type and season were species and isotope dependent. The estimates of littoral resource use based on fin isotope ratios were between 13% and 36% greater than those based on muscle across species. Season affected this difference for some species, suggesting the potential importance of using season-specific conversions when working with non-lethal tissues. Fin and muscle stable isotopes produced similar estimates of trophic position for northern pike and yellow perch, but fin-based estimates were 0.2-0.4 trophic positions higher than muscle-based estimates for lake whitefish. The effect of season was negligible for estimates of trophic position in all species. Strong correlations existed between fin and muscle δ13 C and δ15 N values for all three species; thus, linear conversion relationships were developed. The results of this study support the use of non-lethal sampling in stable isotope studies of fishes. The authors suggest that researchers use tissue conversion relationships and account for seasonal variation in these relationships when differences between non-lethal tissues and muscle, and seasonal effects on those differences, are large relative to the scale of isotope values under investigation and/or the trophic discrimination factors under use.

The study was conducted to identify the protozoan parasites in a freshwater indigenous air breathing fish, Anabas testudineus. The host fish was collected during mid of the April 2018 to end of the March 2019 from freshwater bodies of Mymensingh, Kishoregonj, Faridpur, Jashore, Manikganj and Bogura districts of Bangladesh. Five species of phylum myxozoa namely Henneguya gigas, Henneguya mystusia, Henneguyaa cerinae, Henneguya periophthalmusi and Myxidium sp., three species of phylum ciliophora namely Amphileptus disciformis, Epistylisl woffi and Trichodina anabasi and one species of phylum mastigophora namely Trypanosoma anabasi were identified in A. testudineus. Myxozoans (97.55%) were clearly dominant group than chiliophorans (2.45%). Bangladesh J. Zool. 49 (2): 331-345, 2021

Aim: To assess the optimum protein and lipid requirement of Anabas testudineus at its fry stage, based on the growth performance, feed efficiency and nutrient gain efficiency. Methodology: Eight experimental diets were prepared with four protein (35, 40, 45 and 50 %) and two lipid (9 and 13%) levels. The diets were designated as D1 (35 P/9L), D2 (35 P/13 L), D3 (40 P/9 L), D4 (40 P/13 L), D5 (45 P/9 L), D6 (45 P/13 L), D7 (50 P/9 L) and D8 (50 P/13 L). Each of the experimental diets was fed to triplicate groups of 10 fishes with an average individual body weight of 1.23 g in 24 glass aquaria. The diets were fed at about 4 % body weight per day in two equal rations for a period of 60 days. Results: Significantly (p 0.05) food conversion ratio (1.45) was observed in fish fed with diet D5 (45% protein and 9% lipid). The nutrient retention parameters like protein retention, protein productive value, lipid productive value and apparent net protein utilization were also significantly (p < 0.05) high in the treatment group D-5 fed with diet containing 45% protein and 9% lipid. Significantly (P

The purpose of the research is determination of the species composition of parasites of cyprinid and percoid fish in the reservoirs of the Moscow Canal.Materials and methods. In 2019–2020, parasitological material was collected in the spring, summer and autumn from percoid (the pike perch and European perch) and cyprinid fish (the bream, silver bream, roach, rudd and sabrefish) aged 2 to 7 years from the reservoirs of the Moscow Canal (Ikshinsky, Pestovsky, Pyalovsky and Klyazminsky Reservoirs) by the methods generally accepted in ichthyo-parasitology. To quantify the fish infection rate, we used the incidence or prevalence of infection, the intensity of infection, and the mean amplitude of the intensity of infection. We used Kabiosh index (K) to assess the species diversity of parasites. Results and discussion. The parasitological analysis results of percoids and cyprinids from the reservoirs of the Moscow Canal are presented. 34 parasite species were found in fish, which belong to nine taxonomic groups: Microsporidia, Myxosporea, Monogenea, Cestoda, Trematoda, Nematoda, Acanthocephala, Hirudinea, Crustacea. The largest number of species belongs to trematodes, the rest, taxa (mixo- and microsporidia, cestodes, nematodes, acanthocephalans, leeches and parasitic crustaceans), are represented singly. We calculated the species diversity ratio (R) of fish parasites in the reservoirs, which ranged from 0.335 to 0.575, which indicates the fauna similarity from 50 to 75%. The greatest similarity in the parasite fauna was found in the roach (R = 0.168–0.447), the least in the European perch (R = 0.447–1.0). We have identified the dominant species that are found in more than 20% of the studied fish and determine the “core” of the parasitic fauna, which included 4 parasite species of epizootic and 1 parasite species of epidemiological significance.

Purpose The present study investigates the fish parasite fauna from Lake Tollense, Mecklenburg-Western Pomerania, Germany. Methods A total of 117 perch (Perca fluviatilis), bream (Abramis brama) and roach (Rutilus rutilus) were sampled for parasites during 2018 and 2019 from Lake Tollense and compared with earlier data from Lake Malchin and Lake Hohen Sprenz in 2011 and 2014, respectively. Parasites were identified based on morphological and molecular characters. Results A total of 32 parasite species were isolated from fishes of Lake Tollense, predominated by digeneans. Diplostomum baeri was found only in perch while D. spathacaeum was isolated from bream and roach. Parasite comparison of similar hosts between lakes revealed highly abundant Ichthyocotylurus spp. in perch and bream of Lake Malchin while Aspidogaster limacoides was most common in roach from Lake Tollense. Diversity indices of roach showed significant variation between localities. However, NMDS graph revealed separation of the three freshwater habitats based on the parasite fauna of perch, bream and roach. Conclusion Based on the multivariate statistical analysis, the three natural inland water bodies could be distinguished based on the parasite communities of perch, bream and roach. The potential to utilise fish parasites as biological indicators in freshwater ecosystem is discussed.

The long-term dynamics (over more than 70 years) of pike infection by cestodes Triaenophorus crassus and T. nodulosus in the Rybinsk Reservoir (the Volga River) has been studied in a comparative aspect. Cestode T. crassus is an invasive species that has entered the reservoir together with vendace Coregonus albula (the second intermediate host) from Lake Beloe; T. nodulosus is a native species that develops with the involvement of perch as a second intermediate host. Climate warming in the Rybinsk Reservoir manifests itself in a consistently growing average water temperature. This has led to a gradual decrease in the rate of pike infection by cestode T. crassus as a result of disturbances in the set of complex ecological relationships between the parasite and its hosts: a decrease in the abundance of large pike, fluctuations in the reservoir water level, and mass death of vendace in years with abnormally hot summers and the alternation of strong and weak year-classes in this short-cycle species (age 1+ to 3+). The long-term dynamics of pike infection by T. nodulosus is characterized by its consistently high rates and slight fluctuations. The abundance of perch population in the Rybinsk Reservoir remains high, and its age composition is stable, which contributes to a high rate of infection of both perch and pike by T. nodulosus. Cestode T. crassus occurs only in large pike (30 cm long or more); the rate of infection increases with age; T. nodulosus parasitizes mainly young pike (starting from young of the year), with the infection rate decreasing in large pike.

It is already known that domestication modifies stress and immune responses in juveniles and adults of several fish species. However, there is a lack of information on whether these modulations result from adaptability along the life cycle or if they are pre-determined in very early developmental stages. To shed light on mechanisms that help to explain the process of domestication, a study was conducted to analyze comparatively Eurasian perch larval performance, stress, and immune status between wild and domesticated specimens. Eurasian perch larvae obtained from wild and domesticated (generation F5 reared in recirculating aquaculture systems) spawners were reared in the same conditions during the main rearing trial (MRT) and also subjected to a thermal challenge (TC). During the study, larval performance (including survival, growth performance, swim bladder inflation effectiveness, deformity rate), the expression of genes involved in immune and stress response, and the specific activity of oxidative stress enzymes (during MRT only) were analyzed. No significant differences in hatching rate, deformity rate, or swim bladder inflation effectiveness between wild and domesticated larvae were found, whereas specific growth rate, final total length, and wet body weight were significantly lower in wild larvae. Higher mortality was also observed in wild larvae during both MRT and TC. The data obtained in this study clearly indicated that during domestication, significant modifications in stress and immune response, such as complement component c3, were noted as early as just after hatching. Generally, domesticated fish were characterized by a lower stress response and improved immune response in comparison to the wild fish. This probably resulted from the domesticated larvae being better adapted to the conditions of artificial aquaculture. The data obtained provided information on how domestication affects fish in aquaculture, and they contribute to the development of efficient selective breeding programs of Eurasian perch and other freshwater teleosts.

Fragmentation of river systems by dams can have substantial genetic impacts on fish populations. However, genetic structure can exist naturally at small scales through processes other than isolation by physical barriers. We sampled individuals from five native fish species with varying life histories above and below a dam in the lower Boardman River, Michigan, USA, and used RADseq to investigate processes influencing genetic structure in this system. Species assessed were white sucker Catostomus commersonii, yellow perch Perca flavescens, walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and rock bass Ambloplites rupestris. We detected significant differentiation within each species, but patterns of population structure varied substantially. Interestingly, genetic structure did not appear to be solely the result of fragmentation by the dam. While genetic structure in yellow perch and walleye generally coincided with “above dam” and “below dam” sampling locations, samples from our other three species did not. Specifically, samples from rock bass, smallmouth bass, and, to a much lesser extent, white sucker, aligned with a putative Great Lakes (GL) group that contained mostly individuals sampled below the dam and a putative Boardman River (BR) group that contained individuals sampled both above and below the dam, with some evidence of admixture among groups. We hypothesize that the GL and BR groups formed prior to dam construction and our samples largely represent a mixed stock that was sampled sympatrically outside of the spawning season. Support for this hypothesis is especially strong in smallmouth bass, where GL fish were 151 mm smaller than BR fish on average, suggesting a potential ontogenetic habitat shift of young GL fish into the lower river for feeding and/or refuge. Our study illuminates the complex dynamics shaping genetic structure in fragmented river systems and indicates that conclusions drawn for a single species cannot be generalized.

In the present study, the authors investigated the effect of acclimation duration (up to 4 h) on behavioural characteristics of taxonomically and functionally different fish species, i.e., the migratory rheophilic salmonids rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), and the non-migratory eurytopic European perch (Perca fluviatilis) and three-spined stickleback (Gasterosteus aculeatus). Specifically, the authors explored fish behavioural patterns based on specific endpoints (average, maximum and angular velocity) during the acclimation period, and determined the acclimation period suitable for the tested fish species. The performed behavioural data analysis showed that the minimum time needed to adjust fish activity to a more stable (baseline) level should be at least 2 h for O. mykiss and S. salar and 1 h for G. aculeatus. Nonetheless, P. fluviatilis behaviour did not show significant changes during the 4 h acclimation. The results of this study revealed that the effect of the acclimation duration on such rheophilic species as O. mykiss and S. salar was greater than that on the eurytopic species P. fluviatilis and G. aculeatus, indicating that acclimation period is important in managing fish stress before behavioural observations. For all species, the highest variability was found in the endpoint of maximum velocity, and the lowest in that of angular velocity. This study showed that before starting actual toxicity testing experiments, it is important to determine an appropriate, species-specific acclimation period.

Biological invasions are a serious problem in natural ecosystems. Local species that are potential prey of invasive alien predators can be threatened by their inability to recognize invasive predator cues. Such an inability of prey to recognize the presence of the predator supports the naïve prey hypothesis. We exposed eggs of a damselfly, Ischnura elegans, to four treatments: water with no predator cue (control), water with a native predator cue (perch), water with an invasive alien predator cue (spinycheek crayfish) that is present in the damselfly sampling site, and water with an invasive alien predator cue (signal crayfish) that is absent in the damselfly sampling site but is expected to invade it. We measured egg development time, mortality between ovipositing and hatching, and hatching synchrony. Eggs took longer to develop in the signal crayfish group (however, in this group, we also observed high green algae growth), and there was a trend of shorter egg development time in the spinycheek crayfish group than in the control group. There was no difference in egg development time between the perch and the control group. Neither egg mortality nor hatching synchrony differed between groups. We suggest that egg response to signal crayfish could be a general stress reaction to an unfamiliar cue or an artifact due to algae development in this group. The egg response to the spinycheek crayfish cue could be caused by the predation of crayfish on damselfly eggs in nature. The lack of egg response to the perch cue could be caused by perch predation on damselfly larvae rather than on eggs. Such differences in egg responses to alternative predator cues can have important implications for understanding how this group of insects responds to biological invasions, starting from the egg stage., Damselfly eggs were exposed to three predators cues: 1 native—perch and two alien crayfish: signal (not present in sites where damselflies were collected) and spinycheek (present in site where damselflies were collected). Egg development time, hatching synchrony, and eggs mortality were checked. Eggs developed to hatching faster in the presence of spinycheek crayfish (egg predator), slower in signal crayfish group, and no effect of perch (larvae predator) were found.

Studies have demonstrated that hurricanes can drive selection in Neotropical anoles. In a recent study, it was shown that post-hurricane survivors showed longer toepad areas and, surprisingly, shorter femurs. 2. One potential explanation for the reduction in femur length is that increased drag on individuals with longer femurs causes them to be blown off their perch. Consequently, lizards with shorter femora might survive better in hurricanes. 3. To gain insight into the form-function relationships of drag reduction in perched lizards exposed to high-velocity winds, we quantified drag forces on Anolis lizard models in realistic grasping positions using computational fluid dynamics. 4. We showed that overall drag, as well as the relatively high drag at the hindlimbs strongly increase with the distance of the pelvic region from the perch. As optimal postures to resist sustained arboreal pulling involve extended limbs, longer hindlimbs increase the chance of having the limbs and pelvic region positioned outside the zone in which efficient shielding from the wind by the perch occurs. 5. Our study underlines the complexity of performance trade-offs on the evolution of limb morphology in arboreal lizards, and emphasizes the importance of generally ignored functions such as aerodynamic drag reduction in arboreal ecosystems.

Measures for consumer protection against food adulteration and misleading labeling are integrated into EU legislation, including methods for detection of misleading practices. Verification of meat content is available for marine products but not for freshwater fish because of the lack of standard nitrogen factors. The aim of this study was to establish nitrogen factors for European pike-perch Sander lucioperca (Linnaeus, 1758), northern pike Esox lucius Linnaeus, 1758, and sheatfish Silurus glanis Linnaeus, 1758. The study involved analysis of 808 fillet samples obtained in spring (March–April) and autumn (October–November) harvest seasons, 2018–2019, from seven Czech Republic fish rearing facilities. Samples with and without skin were analyzed for nitrogen content, dry matter, protein, ash, and fat according to established ISO methods. The recommended nitrogen factor for European pike-perch with the skin is 3.28 ± 0.09 and without the skin is 3.21 ± 0.09; for northern pike with the skin is 3.18 ± 0.09 and without skin is 3.15 ± 0.09; and for sheatfish with skin is 2.73 ± 0.13 and without skin is 2.75 ± 0.12. The established nitrogen factors will enable analysis of meat content to ensure that consumers are purchasing correctly described and labeled fish products.

The Eurasian perch (Perca fluviatilis Linnaeus, 1758) is native to almost entire Eurasia. For over the last two decades, this species became an important candidate for intensive freshwater aquaculture due to its high consumer’s acceptance and overall market value. Hence, the intensive production of Eurasian perch has increased considerably allowing effective domestication; there is still a need for the development of effective selective breeding programmes allowing its further expansion. This process, in turn, can be significantly facilitated by molecular genetics. The genetic information of Eurasian perch and its populations is limited. Up to date information of regarding genetic diversity of many populations is still missing, including microsatellites for Eurasian perch, which could be useful during the selective breeding programmes allowing parental assignment and/or to follow heritability of desired traits. In this study, we have developed and characterized new polymorphic microsatellites. Subsequently, those 12 markers have been used further to compare two Hungarian and one Polish Eurasian perch populations. The Hungarian stocks had high genetic similarity (with low diversity), as we assumed, while the Polish population differed significantly. All populations deviated significantly from the Hardy–Weinberg equilibrium, and heterozygote deficiency was detected in all, showing the presence of an anthropogenic effect.

The study was conducted with funding support from SEAFDEC Aquaculture Department (Study code: Nr-01-F2013B).

European perch (Perca fluviatilis Linnaeus, 1758) is widespread in water basins and has a commercial value. However, in the natural environment, fish are often infected with invasive diseases, which exclude its processing for food purposes. Being in the body of fish, parasites produce toxic substances that affect various organs of fish. Widespread in the Volga Delta pathogenic species, Eustrongylides excisus, in large quantities occurs in perch in larval state in the abdominal cavity of the body, in the walls of the intestine, in the liver, in the calf and in the spinal muscle tissue, reaching up to 30 or more parasites per fish. Sexual maturity of the parasite occurs in the stomach of the birds. This disease is peculiar to perch species; larvae of this nematode cause granulomatous inflammatory reaction. In addition, these worms, penetrating deep into the muscles of the perch, spoil the commercial quality of fish, which leads to the culling of fish raw materials and rejection of foodstuff. This work, for the first time, compares the hematological status of infected and healthy perch of natural populations. The work aimed to assess biological and physiological effects of various parasitic invasions on European perch Perca fluviatilis(Linnaeus, 1758). Fish of both sexes at the age from 0 to 4 years were caught in natural reservoirs of the Lower Volga (Bolshaya Bolda and Bely Ilmen rivers, Astrakhan region) in September 2016 to June 2019. The total body length, the length to the end of the scale cover, body weight and age were determined, and the Fulton’s fatness coefficient was calculated. The skin, fins, mouth, gills, eyes, heart, abdominal cavity, muscles, brain, and spinal cord of fish were examined for parasitological contamination. Blood for analysis was taken from the tail vein in vivo. Nematodes were found in more than 55 % of the caught perch. Nematodes were found in the liver (30 %), abdominal cavity (45 %), intestines (10 %), muscles (15 %), and gills (5 %). Parasites were found free within the body cavity, or encapsulated, with Eustrongylides excisus being the most abundant. In the infected fish, the average body weight and body condition coefficient decreased as compared to the healthy fish of the same age. However, the revealed growth retardation in the infected perch was statistically insignificant (p > 0.05), while the body condition coefficient was significantly lower than in uninfected fish (p < 0.01 for 3-year-old perch). The parasitic infestation of P. fluviatilis with Eustrongylides nematode caused symptoms of anemia, suppression of erythropoiesis (i.e., a decrease in the proportion of blast forms of the erythrocytic cell series), an increase in the proportion of neutrophils, monocytes, and lymphoblasts in the leucocyte count. In infected perch, the number of red blood cells significantly decreased (83.01×104±4.17×104 vs. 137.22×104±5,26×104/mm3), as well as the concentration of total protein (40.81±1.19 vs. 48.97±2.07 g/l) and blood cholesterol (5.17±0.28 vs. 6.81±0.30 mmol/l). MCH (mean corpuscular hemoglobin), erythrocyte sedimentation rate, the total number of leukocytes and platelets also increased compared to uninfected fish. The level of pathological red blood cells increased in the infected perch (9,17±0,23 % vs. 4,87±0,11 %). Changes in cell cytoplasm and nucleus, degenerative changes in the cell, changes associated with cell division were the main types of the discovered cell pathology of the infected perch.

The paper reports the study of macroparasite load and aggressiveness of the European perch Perca fluviatilis juveniles of different size captured in the Rybinsk Reservoir (Volga River). A total of 13 macroparasite species have been identified with the Tylodelphys sp. and Ichthyocotylurus sp. trematodes and the Triaenophorus nodulosus cestode being the most abundant ones. A statistically significant correlation between the invasion intensity and fish size and aggressiveness has been found only for T. nodulosus. The possible mechanisms underlying T. nodulosus plerocercoid effects on the size and behavior of their fish hosts, the parasite transmission to the final host, and phenotypic differentiation in perch populations are discussed.

The large-sized tapeworm Dibothriocephalus latus is known as the broad or fish-borne cestode of mammals that is capable to infect humans and cause diphyllobothriosis. Recently, molecular data on D. latus has been accumulating in the literature and a complete genome sequence has been published; however, little is known about the karyotype and chromosome architecture. In this study, an in-depth karyological analysis of 2 D. latus specimens was carried out. The plerocercoids originated from a perch caught in subalpine Lake Iseo (Italy) and the tapeworms were reared in hamsters. Both specimens contained cells with a highly variable number of chromosomes ranging from18 to 27. Nevertheless, the largest portion of mitotic figures (47%) showed a number corresponding to the triploid set, 3n = 27. Accordingly, the karyotype of the analyzed specimens consisted of 9 triplets of metacentric chromosomes. Fluorescence in situ hybridization (FISH) with the 18S rDNA probe clearly demonstrated the presence of 3 clusters of hybridization signals on the triplet of chromosome 7, thus confirming the triploid status of the specimens. FISH with a telomeric (TTAGGG)n probe confined hybridization signals exclusively to the terminal chromosomal regions, supporting the earlier findings that this repetitive motif is a conserved feature of tapeworm telomeres.

Phenotypic plasticity can be expressed as changes in body shape in response to environmental variability. Crucian carp (Carassius carassius), a widespread cyprinid, displays remarkable plasticity in body morphology and increases body depth when exposed to cues from predators, suggesting the triggering of an antipredator defense mechanism. However, these morphological changes could also be related to resource use and foraging behavior, as an indirect effect of predator presence. In order to determine whether phenotypic plasticity in crucian carp is driven by a direct or indirect response to predation threat, we compared twelve fish communities inhabiting small lakes in southeast Norway grouped by four categories of predation regimes: no predator fish, or brown trout (Salmo trutta), perch (Perca fluviatilis), or pike (Esox lucius) as main piscivores. We predicted the body shape of crucian carp to be associated with the species composition of predator communities and that the presence of efficient piscivores would result in a deeper body shape. We use stable isotope analyses to test whether this variation in body shape was related to a shift in individual resource use—that is, littoral rather than pelagic resource use would favor the development of a specific body shape—or other environmental characteristics. The results showed that increasingly efficient predator communities induced progressively deeper body shape, larger body size, and lower population densities. Predator maximum gape size and individual trophic position were the best variables explaining crucian carp variation in body depth among predation categories, while littoral resource use did not have a clear effect. The gradient in predation pressure also corresponded to a shift in lake productivity. These results indicate that crucian carp have a fine‐tuned morphological defense mechanism against predation risk, triggered by the combined effect of predator presence and resource availability., The crucian carp develops a deep body when exposed to cues from predators and represents a classic example of anti‐predator defense mechanism in fish. In this study, we showed that crucian carp body depth increased with decreasing trophic position and increasing predation risk represented by predator gape size. Our results indicate that crucian carp have a fine‐tuned morphological defense mechanism against predation risk, triggered by the combined effect of predator community and resource use.

The response of macrophage aggregates in fish to a variety of environmental stressors has been useful as a biomarker of exposure to habitat degradation. Total volume of macrophage aggregates (MAV) was estimated in the liver and spleen of white perch Morone americana from Chesapeake Bay using stereological approaches. Hepatic and splenic MAV were compared between fish populations from the rural Choptank River (n = 122) and the highly urbanized Severn River (n = 131). Hepatic and splenic MAV increased with fish age, were greater in females from the Severn River only, and were significantly greater in fish from the more polluted Severn River (higher concentrations of polycyclic aromatic hydrocarbons, organochlorine pesticides, and brominated diphenyl ethers). Water temperature and dissolved oxygen had a significant effect on organ volumes, but not on MAV. Age and river were most influential on hepatic and splenic MAV, suggesting that increased MAV in Severn River fish resulted from chronic exposures to higher concentrations of environmental contaminants and other stressors. Hemosiderin was abundant in 97% of spleens and was inversely related to fish condition and positively related to fish age and trematode infections. Minor amounts of hemosiderin were detected in 30% of livers and positively related to concentrations of benzo[a]pyrene metabolite equivalents in the bile. This study demonstrated that hepatic and splenic MAV were useful indicators in fish from the 2 tributaries with different land use characteristics and concentrations of environmental contaminants. More data are needed from additional tributaries with a wider gradient of environmental impacts to validate our results in this species.

Early life stages of fishes are critical stages due to their importance in enhancing recruitment. Given the high mortality through the embryonic and larval stages, managers have started investigating factors that impact these stages. Environmental factors, such as water temperature, have been found to play a larger role in early life survival. Climate change predications will be more apparent in northern temperate systems like the Great Lakes. Yellow perch Perca flavescens are an important sport fish in the region whose populations have been declining since the 1980s. Yellow perch recruitment is highly erratic due to the species dependence on spring water temperatures. With warming waters occurring earlier in the seasons, it is unsure how wild yellow perch will adapt. The objective of this study was to determine how variations in temperature regimes during the egg incubation period would impact embryonic and larval development in yellow perch. Four different temperature treatments were used in this study: steady temperature at 16°C, a gradient starting at 12°C increasing by 1-2°C every 3-4 days, a heat shock on day six of 20°C for 16 hours to mimic a heat wave event, and finally, a cold shock on day six of 10°C temperatures for 16 hours to mimic a cold snap event. The results of this study confirm that water temperatures severely impact embryonic development and incubation periods of yellow perch, having a significant impact on the percent of failed larvae at the end of the incubation period (P= 0.0005), with the cold shock affecting the lowest percent of failed larvae (0.8%) while the steady treatment had the highest percent (22.9%). Temperature treatment did have a significant impact on the time it took for larvae to successfully hatch out (P

Understanding how birds utilised songs and calls to communicate among conspecifics is crucial for their survival, yet it remains an understudied area in bird ecology. We studied the influence of perch height selection on the vocalisation of Pied Triller, a common garden bird, in two suburban landscapes namely Pustaka Negeri Sarawak Recreational Park, Kuching and Universiti Malaysia Sarawak campus, Kota Samarahan from October 2018 to February 2019. Using a Marantz recorder connected to a parabolic reflector, we recorded calls and songs during morning (0630-1030 hr) and late afternoon (1600-1830 hr). Perch object, tree species, roost substrate and perch height from the ground were identified and measured. Clear and good quality spectrograms were used directly to describe song and call types. Photos and video recordings were analysed to describe perch behaviour. The vocal output representatives were then matched to the corresponding behaviour displayed. Our results revealed that Pied Trillers emit four different vocal outputs namely (i) song type, (ii) call type A, (iii) call type B and (iv) call type C. A total of nine behaviours were observed, of which the perch-hop behaviour was observed the most from both male and female Pied Trillers (33.71%), followed by perching (29.21%), foraging (20.22%), preening (7.78%), defecating (2.25%), eating (2.25%), roosting (2.25%), bill wipe (1.12%) and flight (1.12%). They prefer to roost on high perch to emit calls compared to songs. This probably suggest that Pied Triller prioritised vocal transmission and signalling to avoid being masked by surrounding anthropogenic noises and to avoid being conspicuous to potential predators. The most frequently visited perch object was the Weeping fig tree, Ficus benjamina. Keywords: Call, perch height, Pied Triller, song, suburban landscapes

Through using different sources, population reintroductions can create genetically diverse populations at low risk of harmful inbreeding and well equipped for adaptation to future environments. Genetic variation from one source can mask locally nonoptimal alleles from another, thereby enhancing adaptive potential and population persistence. We assessed the outcomes in survival, growth and reproduction of using two differentiated sources (genetically diverse Yarra and moderately diverse Dartmouth) for translocations and stocking to reintroduce the endangered Australian freshwater Macquarie perch Macquaria australasica into the Ovens River. For stocking, same‐ and different‐population parents (“cross‐types”) were used during hatchery production. Genetic samples and data on individual fish were collected over three years of monitoring the Ovens. We genetically assigned Ovens fish to their broodstock parents and tested whether cross‐type and genetic dissimilarity between parents are associated with offspring survival, and whether cross‐type and parental dissimilarity or individual genetic diversity are associated with somatic growth rates of stocked fish. We genetically identified translocated fish and assessed local recruit ancestry. Of 296 Ovens fish, 31.1% were inferred to be stocked, 1.3% translocated and 67.6% locally born. Cross‐type strongly predicted survival of stocked offspring: those with two Yarra parents had the highest survival, followed by offspring with two‐population, then Dartmouth, ancestry. Of the Ovens recruits, 59.5% had Yarra, 33.5% two‐population and 7.0% Dartmouth ancestry, despite 67% of stocked and 98% of translocated fish originating from Dartmouth. Offspring with two Yarra parents grew faster than offspring of Dartmouth or two‐population ancestry. Although Dartmouth fish appear to be less fit in the Ovens compared to Yarra fish, possibly due to deleterious variation or genetic or plastic maladaptation, they contribute to the reintroduced population through local interbreeding with Yarra fish and relatively high survival of stocked offspring of two‐population ancestry. Thus, combining compatible stocks is likely to benefit restoration of other wildlife populations.

The number of pores in the seismosensory canals of several paired integumentary head bones was counted for specimens of the roach and European perch caught in 15 small ponds in the central–eastern part of the Udmurt Republic, Russia. Three indices of fluctuating asymmetry were calculated on the dataset obtained, and a statistical analysis of the relationships of these indicators with the average (over several years) mineralization of water bodies for different periods of the growing season and with their variation coefficients has been carried out. In the roach, the average proportion of asymmetric variants of the studied traits was significantly associated with seasonal variability of mineralization values only, while close and statistically significant relationships between this indicator and the average mineralization values ​​in individual periods of the growing season have been found in the European perch. Similarly, another indicator of the roach, the variance of fluctuating asymmetries of the total values ​​of paired meristic signs of the cranial seismosensory system, was similarly associated with these values. Possible mechanisms of the influence of the mineralization factor on the degree of asymmetric manifestation of the studied signs are discussed, taking into account the features of their gradual formation in the early ontogenesis of the two fish species. As a result, some limitations on the adequate use of these indicators in the bioindication of anthropogenic pollution of freshwater by dissolved inorganic substances are considered.

Background European species of the large genus Phyllodistomum Braun, 1899 had historically been erected based solely on morphological characters. Unfortunately, many of them are still poorly known and inadequately described. Molecular approaches are critical to delineate species which were impossible to differentiate based on morphology alone. Methods New samples of adult Phyllodistomum spp. were collected from the urinary bladder and/or ureters of European freshwater fishes and fixed to conduct a light and scanning electron microscopy study, and to obtain sequences of nuclear (ITS2 spacer and 28S rRNA gene), to be analysed in the context of a molecular phylogeny. Results Based on new findings, a new species of Phyllodistomum from the urinary bladder of the European perch, Perca fluviatilis, in Volga River basin, Russia, is described. Additionally, new data on the morphology and tegumental surface topography of P. macrocotyle (Lühe, 1909) Odhner, 1911 from ureters of the common rudd, Scardinius erythrophthalmus, is presented. The host range of P. folium, confirmed by DNA analysis, is extended to other cyprinid fish species. Conclusions The present study has again shown that species of the genus Phyllodistomum are in dire need of revision based on both molecular analysis and detailed morphological redescriptions of the forms attributed to the genus. Morphologically, P. kupermani n. sp. most closely resembles P. pseudofolium, a highly host-specific parasite of Gymnocephalus cernuus (L.), but molecular phylogenetic analyses based on ITS2 and 28S rDNA sequences showed that these species are distantly related. Phyllodistomum kupermani n. sp. was found to be phylogenetically most closely related to the type-species of Phyllodistomum, P. folium. Phylogenetic analyses revealed that Phyllodistomum kupermani n. sp. and P. folium formed a clade with other freshwater species for which cystocercous cercariae develop in bivalves of the family Sphaeriidae. The micromorphology and tegumental surface topography of P. macrocotyle revealed in the present study provide a valuable taxonomic criterion for congeneric species differentiation.

Results of studies on nutrition of juvenile fishes of the Curonian Lagoon of the Baltic Sea are presented. Material on young-of-the-years nutrition was collected in October 2016 during the expeditions of «AtlantNIRO» at 14 standard stations in the Curonian Lagoon. A total of 418 specimens of young-of-the-years were collected and processed. Juveniles of fishes of the Curonian Lagoon were represented by 10 species: pikeperch, bream, roach, perch, smelt, ruffe, three-spined stickleback, ninespine stickleback, bleak and sabrefish. Planktonic and benthic invertebrates formed a basis of the young-of-the-years diet. In most species of juvenile fishes, the nutritional spectra did not differ from the nutritional spectra in the range. An exception was juveniles of the ruff and ninespine stickleback, in which planktonic crustaceans predominated in the diet, while in other reservoirs they consumed bottom organisms. Only Cladocera and Copepoda were found in the diet of roach of juveniles; bottom organisms were absent. In the range of roach juveniles, bottom organisms and mollusks prevailed. The food similarity indices for juvenile fish in the Curonian Lagoon are quite high, which may indicate a tension in food relations between juveniles and (or) partial or complete overlap of their food niches. The weakening of food competition is ensured by the divergence of daily dietary peaks. Three-spined and nine-spined sticklebacks as well as a sabrefish and sticklebacks have the closest food spectrum. On the contrary, sabrefish and bream have a different food spectrum. The peculiarity of feeding of pikeperch juveniles in 2016 was the lack of transition to predatory nutrition.

Scorpaeniformes are an important component of commercial and recreational fisheries world-wide. The Neosebastes species, found in the western Pacific and south-east Indian Ocean, have received little attention from a research perspective. Samples of the bighead gurnard perch, Neosebastes pandus, collected from the lower west and south coasts of Western Australia, were used to undertake the first comprehensive investigation of the biological characteristics of a Neosebastes species. Opaque zones in sectioned sagittal otoliths were validated as forming annually. Female N. pandus grow to a significantly larger size, on average, than males and dominate the largest size classes, while males, growing to a smaller size, accumulate in the intermediate size classes. Although males were far less numerous than females in those age classes in which both sexes were found, males and females attain similar maximum ages >25 years. Neosebastes pandus spawns over a brief period between May (austral late autumn) and July (austral mid-autumn) when water temperature and day length are declining. The mean monthly gonadosomatic indices (GSI, IGS ) values of females during the spawning period are 37-50 times higher than those of males, which mature at an earlier age and smaller length compared to females. Histological examination of the ovaries of females indicate that their structure is consistent with "general" teleost ovarian anatomy and thus differs from Scorpaena, Helicolenus and Sebastes species whose ovaries are adapted for specialized reproductive modes. The reproductive strategy of N. pandus of maximizing the reproductive output of females, by this sex attaining a larger size than males and pair spawning (i.e., large disparity in IGS values) demonstrates the close lineage between the Neosebastes and other Scorpaeniformes, such as the Scorpaena, Helicolenus and Sebastes.

Metabolic rates are one of many measures that are used to explain species' response to environmental change. Static respirometry is used to calculate the standard metabolic rate (SMR) of fish, and when combined with exhaustive chase protocols it can be used to measure maximum metabolic rate (MMR) and aerobic scope (AS) as well. While these methods have been tested in comparison to swim tunnels and chambers with circular currents, they have not been tested in comparison with a no‐chase control. We used a repeated‐measures design to compare estimates of SMR, MMR and AS in European perch Perca fluviatilis following three protocols: (a) a no‐chase control; (b) a 3‐min exhaustive chase; and (c) a 3‐min exhaustive chase followed by 1‐min air exposure. We found that, contrary to expectations, exhaustive chase protocols underestimate MMR and AS at 18°C, compared to the no‐chase control. This suggests that metabolic rates of other species with similar locomotorty modes or lifestyles could be similarly underestimated using chase protocols. These underestimates have implications for studies examining metabolic performance and responses to climate change scenarios. To prevent underestimates, future experiments measuring metabolic rates should include a pilot with a no‐chase control or, when appropriate, an adjusted methodology in which trials end with the exhaustive chase instead of beginning with it.

Linear and weight growth of pike perch in the Amur River estuary is considered using the data on age determined for 197 specimens. The growth is described by von Bertalanffy and Schmalhausen equations. Some biological parameters of pike perch as the maximum size, age of mass maturation, etc. are calculated using the age-differentiated coefficients of natural mortality. The growth and biological parameters of pike perch in the Amur estuary are compared with the same parameters of this species in the Amur River at Khabarovsk. Recently 3 ecological forms of pike perch are distinguished in the Amur basin: i) riverine ecotype self-redistributed from Lake Khanka, ii) lacustrine ecotype in the lower Amur River, and iii) highly productive semi-anadromous marime ecotype in the Amur estuary. The 3rd phase of pike perch acclimatization is observed now in the Amur estuary known as the «bloom» phase accompanied with prominent increasing of population abundance and individual growth rate acceleration. Pike perch prey in this area mainly on juveniles of non-anadromous and diadromous fish, or on pond smelt Hypomesus olidus during their concentration in the estuary in winter.

Quantitative metabolomic analysis was performed for eleven tissues of freshwater fish pike-perch (Sander lucioperca), including gill, heart, liver, kidney, spleen, muscle, brain, milt, lens, aqueous (AH) and vitreous (VH) humors with the use of NMR spectroscopy. The absolute values of concentrations were determined for more than 65 most abundant metabolites in every tissue. It was found that from the metabolomic viewpoint, kidney and gill are the most similar tissues, while the metabolomic compositions of ocular tissues—lens, AH, and VH significantly differ from that of other tissues. The combinations of intracellular osmolytes and antioxidants are specific for every tissue. In particular, the concentration of antioxidant ovothiol A in the lens is much higher than in any other tissue, while the brain enjoys the elevated level of ascorbate. The most abundant osmolyte in the fish spleen, muscle, and heart is taurine, and in the brain, gill, and lens—myo-inositol. Other important osmolytes specific for particular tissues are N-acetyl-histidine, N-acetyl-aspartate, betaine, threonine-phosphoethanolamine, and serine-phosphoethanolamine. The quantitative data obtained in the present work can be used as the baseline metabolite concentrations in the fish tissues to evaluate the influence of seasonal, ecological and other factors on the fish metabolism.

Round goby Neogobius melanostomus (Pallas 1814) has become a significant component in the diet of piscivorous fish from the Pomeranian Bay (Bornholm Basin, Baltic Sea). Proper identification of fish species in the diet of predators is significant in biological studies of fish and other aquatic animal species, and, with regard to N. melanostomus, it is important to the knowledge of trophic web structures in areas this species has invaded. A total of 142 individuals of N. melanostomus, measuring 16-174 mm standard length, were examined. Seventy-two fishes were caught during monitoring surveys in fishing grounds, whereas 70 were found in the stomachs of European perch Perca fluviatilis, pike-perch Sander lucioperca and Baltic cod Gadus morhua. The objective of the present study was to analyse the sagittal otoliths to identify variations in outer shape with increases in fish length; expand and correct descriptions of the sagitta, lapillus and asteriscus otoliths; and evaluate the relationships among otolith dimensions and fish standard length. The otoliths were described morphologically. The analysis of the outer shape of sagittal otoliths using Fourier analysis and multivariate statistics exhibited great phenotypic variability that was associated with fish length, including within pairs in individuals and/or among individuals in length classes. In addition, the asterisci and lapilli of N. melanostomus from selected specimens, which were described for the first time with regard to fish length, were found to be less variable compared to sagittal otoliths. This study presents the first analysis of intrapopulation phenotypic plasticity of N. melanostomus sagittal otolith morphology as it is linked to fish size.

The study investigates infection rates of perch by plerocercoids of the Dibothriocephalus latus (Linnaeus, 1758) Lühe, 1899 (syn. Diphyllobothrium latum) broad tapeworm in the creeks of the Krasnoyarsk Water Reservoir and in the Yenisei River (within the limits of the city of Krasnoyarsk). Plerocercoids were found in the perch in all study areas. The rates of invasion of the fish in the Yenisei River and in the creeks of the lower part of the Reservoir – Biryusa and Shumikha – were low (9.8, 6.9, and 13.5%, respectively); the infection of perch was higher in the middle part of the Reservoir, in the Sisim Creek (21.4%). The fish purchased at an unauthorized market was the most infected – 68.5%. The sample included large fish, weighing from 70 to 970 g. A positive correlation was noted between invasion rate and fish age (r=0.7). The plerocercoids found in the fish were viable. They were mainly localized in the fish muscle. Diphyllobothriosis is a commonly occurring helminthiasis in the riverine communities transformed because of the damming of rivers. In the Krasnoyarsk Water Reservoir, the broad tapeworms are usually transmitted along the plankton – perch – pike chain. The data obtained in this study show that small perch, consuming infected plankton, plays a leading role in maintaining the abundance of D. latus in the water reservoir. However, the main contribution to the epidemiological situation in the region is made by the large perch, which is heavily infected with broad tapeworm plerocercoids because of its cannibalistic feeding behavior. Both recreational fishermen and the people purchasing fish at unauthorized markets prefer large perch. Commercial and recreational fishing, settlements on the shores of the Reservoir, and the increasing number of tourists have contributed to the invasion of pathogenic organisms in the Reservoir. The perch caught in the Krasnoyarsk Water Reservoir or in the Yenisei River or purchased at unauthorized markets, which have not been inspected for disease, could be a source of diphyllobothriosis infection for people