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La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Individuals that occupy restricted home ranges for long periods have little chance to sample surrounding habitats and may only be able to respond to changes in the distribution of resources at very local scales. Processes leading to the selection of a home range, therefore, potentially have an important bearing on individual fitness and, ultimately, on population structure. In this study, movements associated with the establishment of home ranges by golden perch (Macquaria ambigua) and common carp (Cyprinus carpio) in an Australian lowland river were examined using radiotelemetry. To examine behaviour associated with exploration and settlement into new home ranges, fish were artificially translocated into an unfamiliar river section. Although there was substantial intraspecific variation in patterns of movement, all fish tracked over the entire study period eventually settled into restricted home ranges. Several fish of both species either moved away from established home ranges and settled in new areas, or undertook large-scale movements and subsequently returned to the original home range. It is suggested that such movements may provide a mechanism by which fish can reap the benefits of home-range occupation whilst still being able to respond to changes in the distributions of spatially and temporally dynamic resources.

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.

Temperature and available food are among the key factors affecting fish during their lifetime. The interaction between foraging and thermoregulatory behavioral responses was studied in experimental conditions using 1+ perch individuals. The behavior of fish was examined in a thermally heterogeneous environment with varying levels of food availability: “excessive” (food objects constituted 20% of the overall fish weight in each compartment of the experimental device), “limited” (3%), and “zero” (0%). The values of the final preferred temperatures revealed in these conditions differed significantly: 26, 24, and 22°С, respectively. In the conditions of excessive food, fish locomotor activity was minimal. The food of juvenile fish consumed over 15 minutes was independent of the number of food objects (20 and 3%) in the experimental device, constituting 14.2 and 15.2% of the fish body weight, respectively. However, fish growth was observed only in the first case, probably due to the higher locomotor activity needed to find and obtain food in the environments with fewer food objects. The data presented may be useful for estimating the dominant forms of behavior of juvenile fish both in experimental and field conditions.

The European perch Perca fluviatilis L. serves as a host of different endohelminths of Trematoda, Cestoda, Nematoda, and Acanthocephala. Its natural range covers freshwater basins throughout much of Europe, including the Danube. Since information about endohelminths of European perch from this international river basin has been rather sporadic, the parasitological examinations of 700 perch from the central region of the Danube river basin in Slovakia were performed in October 2017 and April 2018. The larval stages of Triaenophorus nodulosus (Cestoda) were found in cysts located in the perch liver and adults of Proteocephalus percae (Cestoda) were isolated from the intestine. The larval stages of Eustrongylides sp. (Nematoda) and metacercariae of Clinostomum complanatum (Trematoda), both potential causative agents of fish-borne zoonoses, were found in the musculature. Spatial and seasonal differences in the occurrence of currently detected helminths were discussed with data on biological and environmental conditions of particular sampling site.

The contents of artificial and natural radionuclides of 137Cs, 90Sr, 226Ra, 232Th, and 40K had been investigated in muscle and bone tissues, gill petals, and scales of common perch Perca fluviatilis and pikeperch Sander lucioperca from two fishing areas of the Dnipro (Zaporizhzhia) Reservoir. The specific radionuclide activities were measured with the SEG-001 “AKP-C” and SEB-01-150 scintillation spectrometers of gamma- and beta-radiation energy in Bq/kg of wet weight. The radioactive elements of both natural and artificial origins were concentrated greatly in common perch tissues compared to pikeperch. The bone and muscle tissues contained the maximal levels of radionuclides, while respectively smaller amounts of radionuclides were found in gills and scales. The radionuclide levels in the tissues of investigated fish species were significantly higher in the Dnipro Reservoir area with weak flowage and slow water exchange. Keywords: artificial radionuclides; natural radionuclides; common perch; pikeperch; specific activity; the Dnipro (Zaporizhzhia) Reservoir

Eustrongylides sp. is the most significant freshwater fish zoonotic nematode and has great importance for the environment, fishing and human health. Also the infestation of Eustrongylides excisus being paratenic hosts on pike-perch due to its predator feeding regime. The importance of this nematode is the ability of the capacity to infect carnivorous organisms and humans that feed on them. In this study, Eustrongylides excisus infestation was determined from 51 samples of pike perch (Sander lucioperca L., 1758) between October 2015 and February 2016 from Lake Marmara (Manisa, Turkey). Each sample was observed and the prevalence of the infestation was detected 100%. The parasite samples were examined in Carl Zeiss 300 VP scanning electron microscope. The capsulated and encapsulated parasites were found in various muscles, abdominal cavity and on the internal organs. Also, one sample was detected in the swim bladder without any harm. From scanning electron microscopy overviews, lips and papillae circles were detected on the anterior portion of the body as characteristics for diagnosis of the genus Eustrongylides.

In order to supplement the available information for the eco-hydraulic approach to designing fish passages, taking into account the taxonomic, dimensional structure, as well as taking into account the presence of predatory fish in the stream, the distribution of migratory fish of the boreal plain faunistic complex (Russian Federation) was studied. Three depth-velocity sections from the shore to the midstream were investigated: 5 m and 27.8 cm/s, 8 m and 44.4 cm/s, 11 m and 55.6 cm/s. Analysis of the migration distribution of fish showed that in the direction from the shore to the midstream, the proportion of representatives of Cyprinidae decreases from 41.8–24.3% and that of Percidae decreases from 25.0–18.4%. For individuals of two groups: the Acipenseridae and Lotidae, Coregonidae and Esocidae, patterns of distribution in the structure of migratory fish are opposite – their share increases with increasing speed and depth characteristics: 23.0–40.2% and 10.2–17.1%, respectively. An assessment of the dimensional structure revealed a feature of increase in the size range of fish from the shore to the midstream: the dominance of small individuals ( 30 cm) in the area of higher speeds and depths. A significant difference in the distribution for all studied taxonomic fish groups between the shore and the midstream was shown. Thus, it has been established that for Cyprinidae during the migration period, the choice shifts in favour of minimizing energy costs, and the choice to avoid the risk of predation from individuals of the groups: Coregonidae and Esocidae, and also Percidae, shifts in favour of the former. The distribution of perch is influenced by the reduction of energy costs and the simultaneous avoidance of predation and cannibalism. For the fish group Acipenseridae and Lotidae, their predominance in the deeper area is due to their less developed visual orientation mechanism in the stream because they are bottom-living fish species.

Inter‐relations between water quality and piscivore populations have remained poorly studied but their quantification is crucial for the ecosystem‐based management of inland waters. Here, we aimed to estimate the relative strength of bottom‐up and top‐down trophic interactions between water quality and fish community composition using a comparative approach. Our main hypothesis was that lakes with an abundant piscivore (mainly pikeperch, Sander lucioperca, Percidae) stock would have better water quality than similar lakes with a poor piscivore stock. We used structural equation models on biomass catch per unit of effort data from standard gillnet test fishing to examine the effects of predators (pikeperch, pike [Esox lucius, Esocidae] and piscivorous perch [Perca fluviatilis, Percidae]) on cyprinids (Cyprinidae), and the effects of cyprinids, nutrients, and lake depth on water quality measured as chlorophyll‐a concentration and turbidity. We derived the dataset covering a single summer snapshot of 138 Finnish pikeperch lakes from national databases. Nutrients and lake depth index, the main principal component describing positive effects of nutrient concentrations and negative effects of lake depth, had a positive effect on chlorophyll‐a concentration and turbidity. Pikeperch had a detectable negative effect on both planktivorous and benthivorous cyprinids. While pike also had a negative effect on benthivorous cyprinids, both groups of cyprinids had a positive effect on pikeperch and pike. Supporting the strong, fish‐independent bottom‐up regulation, no significant relationships were detected between the cyprinids and water quality. This study suggests that the bottom‐up effects override the top‐down effects, and despite pikeperch is an efficient piscivore, the observed stock levels did not cascade down to improved water quality. Thus, in lake restoration, reductions of nutrient loading appear more efficient than biomanipulation aimed to strengthen the top‐down links.

Released hatchery-origin fish must survive and reproduce for supplementation to recover collapsed native populations, yet monitoring fitness is challenging, because physical tags are not passed from parent to offspring. Parentage-based tagging (PBT) is a method in which all captive-bred parents are genotyped (i.e., given a molecular tag), and their wild-caught hatchery offspring are identified via genetic pedigree analysis. The sauger (Sander canadensis) is a highly migratory, freshwater percid (perch species), native to central and eastern North America. In the Wind River basin, Wyoming the species’ abundance has declined considerably since 2002, and in 2013 stakeholders initiated a hatchery program to recover the population. We estimated the statistical sensitivity and accuracy of PBT using 17 microsatellites to identify hatchery-origin saugers captured in the wild. We completed in vitro and in silico experiments that demonstrated 98% sensitivity and 99% accuracy of PBT in distinguishing hatcher...

Background. European perch, Perca fluviatilis Linnaeus, 1758, is a predatory freshwater fish present also in the coastal waters of the Baltic Sea. The available catch data indicate that the population profile of this species is disrupted, and the condition of the population is not stable. The aim of this study was to determine the diversity and genetic structure of and assess phylogenetic links and gene flow between selected perch populations originating from various types of reservoirs in northern Poland. Materials and methods. A total of 392 perch were collected from selected bodies of water in north-western Poland and the fin samples were preserved in 96% ethanol or stored for short periods at –20°C. Genomic DNA was isolated, while for further mitochondrial DNA analysis, a 1081-bp fragment of the control region was amplified. Amplification products were sequenced and subjected to restriction analysis (PCR-RFLP) in order to determine the genetic diversity of the control region of mtDNA. The obtained sequences were analyzed using bioinformatics tools, and phylogenetic trees were generated to determine the degree of diversity between individuals in selected perch stocks. Results. Seven haplotypes were identified. Ten polymorphic sites were defined, and the degree of genetic diversity between selected haplotypes was determined. Based on the distribution of perch haplotypes, stocks from Pomeranian Bay (haplotypes F, D), the Szczecin Lagoon (haplotypes D, F, H), and the more homogeneous stocks from Pomeranian Bay (haplotypes F, D) and the Kamieński Lagoon (D, F) can be distinguished. Analysis of phylogenetic relations allowed identifying stocks with the most conserved genome, similar to the standard perch genome, and stocks that have become more genetically distant, probably due to the diversity of the inhabited ecosystems or natural hybridization observed in this species. Conclusion. European perch inhabiting waters of north-western Poland is a species with high plasticity, without isolated stocks or populations that can be clearly distinguished on a genetic basis. It does, however, have a tendency for mitochondrial genomic modifications, which is likely due to the broad spectrum of ecosystems inhabited by the species. Due to the homogeneity of the perch populations from the Szczecin Lagoon, the Kamieński Lagoon, and Lake Myśliborskie, they should be used for the restoration of populations in water bodies in which their genetic structure is severely disrupted. For the same reason, the policy of perch catches should be modified. The authors suggest increasing the protected size to 20 cm and limiting the catches of the species as by-catch by modifying fishing tools, including the introduction of a seasonal prohibition of tools that might eliminate individuals of 15–16 cm in length from natural waters in their spawning period.

The article describes the features of developing major organ systems in pre-larvae and larvae of pikeperch at different stages. In the period of transition to exogenous feeding the nervous, musculoskeletal and digestive systems in pre-larvae body were the most developed. At the same time, cardiovascular, respiratory, excretory systems developed slower. In the beginning of active feeding the digestive, nervous and musculoskeletal systems in pike perch larvae were completely developed: there emerged taste buds, teeth in the oral cavity, were formed cartilaginous tissues, particularly at the skull base. In the cardiovascular system of larvae there continued process of differentiating the heart valves. The research results showed uneven development of main organ systems in pike perch pre-larvae and larvae, which is connected to the development of swim bladder and digestive system during transition to active feeding.

A new Henneguya species, H. jaczoi sp. n., is described from perch (Perca fluviatilis) from Lake Balaton, Hungary. This species infects the palatal region of the fish, forming large plasmodia in the thickened caudal part of the buccal cavity and at the dorsal ends of the cartilaginous gill arches. The species differs from the gill-dwelling Henneguya species of perch and pike (Esox lucius) both morphologically and in molecular aspects. The authors conclude that the type species H. psorospermica Thélohan is a specific parasite of pike, while the species forming plasmodia in the gills of perch corresponds to H. texta Cohn, which was hitherto regarded as a synonym of H. psorospermica. Besides the above-mentioned species, H. creplini was frequently found in pikeperch (Sander lucioperca) and Volga pikeperch (Sander volgensis), but no Henneguya infection has been recorded in ruffe (Gymnocephalus cernua), which is a common percid fish of the lake and is known to be the type host species for H. creplini.

Pike-perch is an invader for the water basins of Central Kazakhstan. These species have stable self-reproductive populations in the regional waters. Back calculation method was used to investigate pike-perch growth rates in reservoirs of K. Satpayev’s channel. For comparison, the data from the other water bodies (Vyacheslavsky and Sherubay-Nurinsky water reservoirs) were used, as well as literature data. Pike-perch species from the investigated waters don’t show high growth rates. The populations from the reservoirs of K. Satpayev’s channel have quite similar growth rates with populations from the Amur river, from a number of reservoirs in the Volga river basin and from the reservoir in Spain. Sexual differences in growth have not been observed. Evaluating possible influence of various abiotic and biotic factors on the growth rate of pike-perch in the reservoirs of K. Satpayev’s channel was carried out. It has been stated that the availability of trophic resources cannot play a key role in growth dynamics because of their high abundance. Morphology of water bodies also does not play a role, as well as chromaticity, turbidity and other optical water indicators. It can be supposed that the main factor influencing growth of pike perch is the habitat’s temperature. This factor hardly ever approaches optimal values for the species in reservoirs of K. Satpaev’s channel. The possible influence of fishing selectivity on pike-perch growth rates was also evaluated. Currently, there has been imposed a moratorium on pike-perch catch. However, pike-perch is found in by-catches and in catches of amateur fishermen. It should be said that such seizures have an insignificant role in the dynamics of growth rates.

The Eurasian perch (Perca fluviatilis) is the most common fish of the Percidae family and is widely distributed across Eurasia. Perch is a popular target for professional and recreational fisheries, and a promising freshwater aquaculture species in Europe. However, despite its high ecological, economical and societal importance, the available genomic resources for P. fluviatilis are rather limited. In this work, we report de novo assembly and annotation of the whole genome sequence of perch. The linked-read based technology with 10X Genomics Chromium chemistry and Supernova assembler produced a draft perch genome ∼1.0 Gbp assembly (scaffold N50 = 6.3 Mb; the longest individual scaffold of 29.3 Mb; BUSCO completeness of 88.0%), which included 281.6 Mb of putative repeated sequences. The perch genome assembly presented here, generated from small amount of starting material (0.75 ng) and a single linked-read library, is highly continuous and considerably more complete than the currently available draft of P. fluviatilis genome. A total of 23,397 protein-coding genes were predicted, 23,171 (99%) of which were annotated functionally from either sequence homology or protein signature searches. Linked-read technology enables fast, accurate and cost-effective de novo assembly of large non-model eukaryote genomes. The highly continuous assembly of the Eurasian perch genome presented in this study will be an invaluable resource for a range of genetic, ecological, physiological, ecotoxicological, functional and comparative genomic studies in perch and other fish species of the Percidae family.

One-hundred age-0 walleye Sander vitreus and 100 age-0 yellow perch Perca flavescens collected in September 2015 from Saginaw Bay, Lake Huron, Michigan, U.S.A., were examined for parasites. Five parasite species (Allacanthochasmus sp., Ichthyocotylurus sp., Bothriocephalus cuspidatus, Camallanus oxycephalus, Ergasilus luciopercarum) infected walleye. Ergasilus luciopercarum had the highest prevalence (97%), mean intensity (9.0), and mean abundance (8.7). Ichthyocotylurus sp. and B. cuspidatus each had a prevalence of 73%. Twelve parasite species (Myxobolus neurophilus, Allacanthochasmus sp., Diplostomum sp., Ichthyocotylurus sp., Neascus sp., Crepidostomum sp., B. cuspidatus, Proteocephalus sp., Dichelyne cotylophora, Eustrongylides tubifex, Philometra cylindracea, Ergasilus luciopercarum) occurred in yellow perch. Ichthyocotylurus sp. had the highest prevalence (72%), mean intensity (7.9), and mean abundance (5.7). Proteocephalus sp. had the next highest prevalence (40%). Walleye and yellow perch are new host records for metacercariae of Allacanthochasmus. Saginaw Bay is a new locality record for M. neurophilus in yellow perch and for C. oxycephalus in walleye. This study is the first survey of the parasites of age-0 walleye and age-0 yellow perch in the Great Lakes.

International audience; In 2016, a total of 5 massive mortality episodes each affecting hundreds of thousands of pike-perch Sander lucioperca larvae occurred at 2 sites in 2 Western European countries. For each episode, perhabdoviruses related to the perch rhabdovirus (PRV) were detected in samples, using either PCR or cell culture combined with PCR. The sequences of the glycoprotein (g), phospho protein (p) and nucleoprotein (n) genes of these samples demonstrated that 2 different genotypes were present at 1 site, each associated with 1 of the 3 episodes. At the other site, a single genotype was associated with the 2 outbreaks. Furthermore, this genotype was strictly identical to 1 genotype involved in the outbreaks of the first site, strongly suggesting a common origin for these 2 viruses. The common origin was confirmed a posteriori because some larvae introduced to both sites had exactly the same geographic origin in Eastern Europe. Taken together, the molecular and epidemiological data suggest that both horizontal and vertical transmission of 2 distinct strains of perhabdoviruses were involved in the various outbreaks affecting pike-perch.

The concentration of sodium and potassium ions in erythrocytes in perch Perca fluviatilis L. was compared to that in ten other freshwater fish species. The cation concentration was determined by flame photometry. The participation of erythrocyte cations in the buffer and respiratory processes that promote the specific resistance of perch to unfavorable factors is substantiated. Among the investigated fish species, the highest sodium concentrations in red blood cells were found in perch and pike, who are the most resistant to water acidification. High sodium concentration in red blood cells indicates a high alkalization capacity of the erythrocytes’ inner environment and is one of the mechanisms for enhanced resistance of perch to water acidification. In perch the potassium concentration in erythrocytes is at the lower limit of the range typical for fish resistant to hypoxia. A high potassium level in red blood cells is regarded as one of the mechanisms for promoting the tolerance of perch to hypoxia. Analysis of data from the literature revealed the same kind of participation of erythrocyte sodium in buffer processes and erythrocyte potassium in respiratory processes in marine fish as in freshwater fish. When determining the level of hematocrit, higher values of this parameter were found in perch as compared to other freshwater fish. Other known physiological and biochemical mechanisms for promoting total and specific resistance of perch to detrimental factors are also analyzed in the paper.

Exploring species-environment relationships to identify essential habitat areas is recognized as an effective way for resource conservation and management. Because of ecological and economic importance of Yellow Perch (Perca flavescens) in Lake Erie, it is essential to develop appropriate habitat models to analyze habitat supply of this species. Empirical species-environment models for two age-groups (juveniles and adults) at two depth strata were developed based on a long-term (27 years) gillnet survey data. Models incorporated interactive terms indicate a high degree of prediction accuracy and satisfied the assumption of residual independence. As a benthivorous species, high-quality habitat is mainly distributed in the bottom waters. Suitable habitat for adults is also found in the mid-waters in the central and east basins. Weighted suitability index per unit area differs significantly among years, basins, and vertical strata. Currently, quota allocation among jurisdictions is determined by using GIS applications of jurisdictional surface area of waters within each management unit. The outputs from our study can be used to revise the current quota allocation schemes and habitat-based quota allocation protocol will provide more scientific and rational total allowable catch for each jurisdiction.

The effects of phenol and its derivatives (4-chlorophenol, 4-nirophenol and 2,4-dinitrophenol) on the activity of peptidases in five species of fish differing in feeding modes have been studied. The power of the effects depends on the fish species and localization of the enzyme (mucosa or chyme). As a rule, in the in vitro conditions the phenols in concentrations of 0.06−0.5 μM/L considerably decreases activities of the intestinal peptidases in bream; silver bream; and, especially, in pike. In some cases, phenol and its derivatives induce an inconsiderable increase in peptidase activities. In zander and perch, in fact, no changes in the enzymatic activity under impact of phenols are observed. It is suggested that the effect of phenol and its derivatives depends to a high extent on the species specificity of peptidases: in the fish of fam. Percidae, the enzymes are relatively tolerant; in fam. Cyprinidae and Esocidae, they are sensitive to the studied toxicants.

Non-native ruffe (Gymnocephalus cernua; family Percidae) were first detected in the Laurentian Great Lakes in 1986, and are not included in regional larval fish keys which were published several years prior to their discovery. In addition, subsequent scientific literature has inconsistently described ruffe larvae. As a result, identification of larval ruffe remains challenging. We used traditional morphology paired with DNA technology to develop diagnostics for ruffe larvae collected in the lower St. Louis River, and compared them to similar species. We found that ruffe < 6 mm total length phenotypically resemble centrarchids, like black crappie, bluegill, and pumpkinseed, but have myomere counts that are intermediate between values for both common percid and centrarchid species. We suggest that developmental and pigment patterns as well as morphometrics can be used to distinguish ruffe from similar species at this size. At larger sizes, ruffe increasingly resemble other percids such as yellow perch, but can be distinguished using myomere counts and morphological features. The findings presented here clarify conflicting descriptions in the scientific literature, and provide additional data to support more confident morphological identification of larval ruffe.

Eurasian perch (Perca fluviatilis) were sampled in April, from May to June and at the end of August to test whether the current season (i.e. feeding conditions) affects the fishes’ stomach size (i.e. volume and weight). A wide range of size data were analysed to reveal the relationship between fish size (length and weight) and stomach size. No significant differences in length-specific stomach volume or stomach weight were found in fish sampled at different times of the year. However, there were differences between seasons in the size of the stomach in relation to body weight, as length-specific body weight changes during the year because of the development of gametes and changes in nutritional status. Both stomach volume and weight grew obeying the power function up to about 20 cm in total length of perch. Yet, the growth was faster than that predicted by the cube law in relation to fish length, i.e. allometric. In larger fish, stomach growth decreased in relation to growth in length, and the relative weight of the stomach even decreased in the largest size class. These dynamics match well with the typical pattern of growth and ontogenic shift in diet from small invertebrates to fish. A non-proportional power function relationship was found between stomach weight and stomach volume. peerReviewed

International audience; Present research suggests that phenotypic variations and consequent potential differences in suitability for commercial culture are more likely to occur among genetically diverse populations. We investigated diversity in traits important to aquaculture and assessed genetic differentiation based on four mitochondrial markers in three European populations of Perca fluviatilis. Using a transplant approach to standardize conditions and minimize environmental effects on phenotype expression, we compared survival, cannibalism, growth rate, growth het-erogeneity, and specific growth rate of the populations to assess whether difference in aquaculture performance (i.e. expression of phenotypical traits that facilitate the rearing of fish and impact the productivity of the farming) is more likely between genetically differentiated populations than between genetically similar populations. We found key traits of performance to differ among allopatric populations, suggesting value in considering geographic source of broodstock. The largest aquaculture performance disparities were observed among genetically differentiated populations. Some lesser differences were observed between allopatric genetically similar populations, possibly the consequence of pre-collection environment, or transgenerational effects.

Recovering populations of piscivores can challenge understanding of ecosystem function due to impacts on prey and to potentially altered food webs supporting their production. Stocks of walleye (Percidae, Sander vitreus), an apex predator in the Laurentian Great Lakes, crashed in the mid-1900s. Management efforts led to recovery by 2009, but recovery coincided with environmental and fish community changes that also had implications for the feeding ecology of walleye. To evaluate potential changes in feeding ecology for this apex predator, we assessed diets in the main basin of Lake Huron and in Saginaw Bay, a large embayment of Lake Huron, during 2009–2011. Walleye switched their diets differently in the main basin and Saginaw Bay, with non-native round goby (Gobiidae, Neogobius melanostomus) and rainbow smelt (Osmeridae, Osmerus mordax) more prevalent in diets in the main basin, and invertebrates, yellow perch (Percidae, Perca flavescens) and gizzard shad (Clupeidae, Dorosoma cepedianum) more prevalent in diets in the bay. Feeding strategy plots indicated that there was a high degree of individual specialisation by walleye in the bay and the main basin. Bioenergetic simulations indicated that walleye in Saginaw Bay need to consume 10%–18% more food than a walleye that spends part or all of the year in the main basin, respectively, in order to achieve the same growth rate. The differences in diets between the bay and main basin highlight the flexibility of this apex predator in the face of environmental changes, but changes in diet can alter energy pathways supporting piscivore production.

Population-level reproductive success (recruitment) of many fish populations is characterized by high inter-annual variation and related to annual variation in key environmental factors (e.g., climate). When such environmental factors are annually correlated across broad spatial scales, spatially separated populations may display recruitment synchrony (i.e., the Moran effect). We investigated inter-annual (1966–2008) variation in yellow perch (Perca flavescens, Percidae) recruitment using 16 datasets describing populations located in four of the five Laurentian Great Lakes (Erie, Huron, Michigan, and Ontario) and Lake St. Clair. We indexed relative year class strength using catch-curve residuals for each year-class across 2–4 years and compared relative year-class strength among sampling locations. Results indicate that perch recruitment is positively synchronized across the region. In addition, the spatial scale of this synchrony appears to be broader than previous estimates for both yellow perch and freshwater fish in general. To investigate potential factors influencing relative year-class strength, we related year-class strength to regional indices of annual climatic conditions (spring-summer air temperature, winter air temperature, and spring precipitation) using data from 14 weather stations across the Great Lakes region. We found that mean spring-summer temperature is significantly positively related to recruitment success among Great Lakes yellow perch populations.

The results of the studies on feeding of zander (Sander lucioperca) underyearlings in the Rybinsk Reservoir in 2008-2010 and 2012 are presented. The study revealed that, at feeding on plankton, the assemblage of the organisms consumed by juvenile zander has not been changed compared to 1950. The underyearlings prefer to feed on large zooplankters—Daphnia longispina, Leptodora kindtii, and Bythotrephes longimanus—along with copepods. At some sampling stations, the species of macrozoobenthos were included in the young zander food. The piscine component of zander food was dominated by underyearlings of Azov-Black sea tyulka (Clupeonella cultriventris); the fries of perch (Perca fluviatilis) and cyprinids (Cyprinidae) were less important. The feeding strategy of zander underyearlings was unchanged in various years. At turning to predatory feeding, not only the ratio of sizes of predator versus prey but also the proportion of the densities of their populations plays an important role.

Spring viremia of carp virus (SVCV) is a rhabdoviral pathogen associated with disease outbreaks in cultured and wild fish worldwide. Common carp (Cyprinus carpio carp), and koi (C. carpio koi) suffer the highest mortalities from SVCV infections, while other cyprinid fish species have varying susceptibility. Although salmonid fish typically are considered refractory to infection by SVCV, there have been a few reports suggesting infection has occurred in rainbow trout (Oncorhynchus mykiss). There have been no reports of Percid fish being infected with SVCV. Since the first North American outbreak of SVCV at a North Carolina koi farm in 2002 there have been eight subsequent detections or outbreaks of SVCV among fish species from the families of Cyprinidae and Centrarchidae within the US and Canada. Thus, this exotic virus is considered a potential threat to native and cultured fish populations in North America. We performed multiple experimental challenges with fish species from three families (Salmonidae, Cyprinidae, and Percidae) to identify the potential risk associated with SVCV exposure of resident fish populations in North America. Three salmonid species, rainbow and steelhead trout (Oncorhynchus mykiss), Chinook salmon (O. tshawytscha), and sockeye salmon (O. nerka), were challenged by immersion or injection with the North Carolina SVCV isolate. Two cyprinid species, koi and fathead minnow (Pimephales promelas) and one percid species, yellow perch (Perca flavescens) were also challenged. Koi were highly susceptible to SVCV up to 11 months of age and fathead minnows had chronic disease expression with moderate mortality (29%). SVCV also induced moderate mortalities (33%) in yellow perch fry. Virus challenged salmonid fish had cumulative percent mortalities ranging from 0 to 100%, with sockeye salmon fry being the most vulnerable. A sub-sample of mortalities and survivors were screened for virus by plaque assay and reverse transcription polymerase chain reaction. In general, all mortalities tested positive for SVCV with high viral titers while survivors had variable persistence of SVCV with overall lower virus titers. Our SVCV challenges of multiple North American fish species suggested that host age is a key factor in determining disease outcome. Other factors, such as fish broodstock, virus strain, water temperature, and rearing conditions in association with the intrinsic level of species susceptibility may also impact infection dynamics. This is the first report of SVCV infecting a species (yellow perch) in the family Percidae and that sockeye salmon fry can suffer similarly high mortalities as the primary SVCV host species.

A transcriptomic comparison suggests an influence of the domestication process on egg quality in Eurasian Perch (Perca fluviatilis). 11. International Symposium on Reproductive Physiology of Fish

Background. Intra cohort cannibalism is one of the main factors that affects the growth and survival of cultured fishes, especially in the larval and juvenile stages. Cannibalism is mainly influenced by extrinsic factors, but intrinsic effects cannot be excluded. As regards the family Percidae, all-female rearing can be advantageous for the fish growth, but does this solution have some impact on cannibalism? The main objective of this study was to investigate potential differences in cannibalism rate and its relation to further growth and survival between mixed-sex and all-female Eurasian perch, Perca fluviatilis Linnaeus, 1758, larvae reared in full-siblings and halfsiblings groups. The additional purpose of this study was to determine whether there was some maternal influence on the cannibalism-survival-growth dynamics in cultured Eurasian perch larvae. Materials and methods. Cannibalism, survival, and growth were studied in mixed-sex and all-female progenies of Eurasian perch larvae. Ten-day old larvae (body weight of 20 mg) originating from the crosses of four parents (two females: f1 and f2; one male: ma; and one neomale: mc) were reared over 77 days at 22°C under the light regime of 16 : 8 (light : dark) in replicated groups consisting of mixed-sex full siblings (f1ma, f2ma), all-female full siblings (f1mc, f2mc), or mixed-sex half-siblings (f1ma + f2ma) and all-female groups (f1mc + f2mc). Results. At the end of the experiment, there was no sexual growth dimorphism and no sex-biased cannibalism. Neither the effect of sibling versus half-sibling groups, nor effects of normal progeny versus all-female population on survival and cannibalism rate were significant. By contrast, maternal effects on cannibalism were observed, chiefly as regards type I cannibalism (partial and tail-first ingestion), and they impacted on survival, as mortality from other causes (complete cannibalism or others) was independent from maternal origin. Conclusion. There is no particular disadvantage of rearing monosex female progenies in term of cannibalism and survival, whereas this culture-management solution is prone to produce long-term advantages for the perch growth, owing to the faster growth of female fish.

Individuals are constantly in competition with one another and, on both ecological and evolutionary timescales, processes act to reduce this competition and promote the gain of fitness advantages via diversification. Here we have investigated the genetic (AFLP) and morphological (geometric morphometrics) aspects of the littoral–pelagic axis, a commonly observed resource polymorphism in freshwater fishes of postglacial lakes. We found a large degree of variation in the genetic and morphological divergence between littoral and pelagic perch and roach across Swedish lakes. Although there was evidence of assortative mating (elevated kinship values) in both species, we could not find any significant coupling of morphology and genetic divergence. Instead, there was evidence that the extent of resource polymorphism may be largely caused by phenotypic plasticity. These results suggest that assortative mating, which can lead to genetically determined adaptive divergence, does occur in these species, particularly perch, but not according to genetically fixed morphological traits. The behavioural mechanisms facilitating associative mating need to be investigated to explore the interaction between phenotypic plasticity and adaptive genetic divergence and their roles in diversification. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 929–940.

To examine size-dependent food web interactions in systems with cannibalism, we compared the abundances of zooplankton and phytoplankton over 2 years in four lakes with cannibalistic perch (Perca fluviatilis) of which two also supported the top predator pike (Esox lucius). The abundance of perch 2 years and older was lower in lakes with pike than in lakes with only perch. In contrast, the abundance of small perch (young-of-the-year and 1-year old) was lower in lakes with only perch suggesting that intense cannibalism reduced these size classes to low levels in lakes lacking pike. Functional response experiments with differently sized perch and zooplankton showed that the attack rate of small perch susceptible to cannibalism was much higher than that of large cannibalising perch. The optimal body size of perch with respect to attack rate was also lower for small zooplankton prey than for large zooplankton. The zooplankton communities in lakes with only perch were dominated by the relatively small species Ceriodaphnia quadrangula and Bosmina spp. and total zooplankton biomass was higher in these lakes than in lakes with both pike and perch. In contrast, the mean size of cladoceran zooplankton was largest in lakes with both pike and perch owing to a dominance of the large zooplankton species Holopedium gibberum in these lakes. We relate these patterns to (1) the low foraging efficiency of large perch on small zooplankton and (2) the low abundance of small zooplanktivorous perch (due to cannibalism) in lakes with only perch. The differences in zooplankton community structure also resulted in different seasonal dynamics of phytoplankton between lakes. Cannibalism introduces a vertical heterogeneity to food webs that causes consumer-resource dynamics that are not predictable from linear food chain models.

The presence of and mechanisms behind density-dependent growth and resource limitation in larval and juvenile stages of organisms with high mortality such as fish are much debated. We compare observed consumption and growth rates with maximum consumption and growth rates to study the extent of resource limitation in young-of-the-year (YOY) roach (Rutilus rutilus) and perch (Perca fluviatilis). Diet, habitat use, consumption rate and growth rate were measured under varying YOY fish densities over 2 years in four lakes. In the first year, YOY roach and perch were studied under allopatric conditions. Experimental addition of perch roe in the second year also allowed study of YOY of the two species under sympatric conditions in two of the lakes. The diet of YOY roach was dominated by cladoceran zooplankton and YOY roach habitat use was restricted to the shore region in both years. This restricted habitat use did not involve any cost in foraging gain in the first year as consumption and growth rates were very close to maximum rates. During the second year, when the two species coexisted, resources were limited in late season, more so in the littoral than in the pelagic habitat in one lake while the reverse was the case in the other lake. The diet of YOY perch was also dominated by zooplankton, and with increasing perch size the proportion of macroinvertebrate prey in the diet increased. After hatching, YOY perch first utilized the pelagic habitat restricting their habitat use to the shore after 1 to several weeks in the pelagic zone. During the larval period, perch were not resource limited whereas juvenile perch were resource limited in both years. The fact that YOY perch were more resource limited than YOY roach was related to the higher handling capacity and lower attack rate of perch relative to roach, rendering perch more prone to resource limitation. Estimates of resource limitation based on consumption rates and growth rates yielded similar results. This supports the adequacy of our approach to measure resource limitation and suggests that this method is useful for studying resource limitation in organisms with indeterminate growth. Our results support the view that density-dependent growth is rare in larval stages. We suggest that density-dependent growth was absent because larval perch and roach were feeding at maximum levels over a wide range of larvae densities.

Transcriptomic analysis of Eurasian perch (Perca fluviatilis) eggs assigned to distinct groups of quality. 6. International Workshop on the Biology of Fish Gametes

A total of 196 yellow perch, Perca flavescens (Percidae), from 3 locations (100 from Strawberry Light in September 2015, 73 from Clinton River Cutoff in November 2017, and 23 from New Baltimore in November 2017) in Lake St. Clair, Michigan, U.S.A., were examined for the digenetic trematode Phyllodistomum superbumStafford, 1904 (Gorgoderidae Looss, 1901). The prevalence, mean intensity, and mean abundance of P. superbum in yellow perch were highest at Strawberry Light (30%, 1.5, and 0.45, respectively) and lowest at Clinton River Cutoff (7%, 1.2, and 0.08, respectively). The maximum intensity of P. superbum varied from 2 to 5 worms per infected fish. Individuals of P. superbum infected the urinary bladder and ureters of perch. Lake St. Clair is a new locality record for P. superbum.

Considering the divergent temperature habitats and morphological traits of four Percidae species: yellow perch (Perca flavescens), Eurasian perch (Perca fluviatilis), pike perch (Sander lucioperca), and ruffe (Gymnocephalus cernua), we stepped into the transcriptome level to discover genes and mechanisms that drive adaptation to different temperature environments and evolution in body shape. Based on 93,566 to 181,246 annotated unigenes of the four species, we identified 1,117 one-to-one orthologous genes and subsequently constructed the phylogenetic trees that are consistent with previous studies. Together with the tree, the ratios of nonsynonymous to synonymous substitutions presented decreased evolutionary rates from the D. rerio branch to the sub-branch clustered by P. flavescens and P. fluviatilis. The specific 93 fast-evolving genes and 57 positively selected genes in P. flavescens, compared with 22 shared fast-evolving genes among P. fluviatilis, G. cernua, and S. lucioperca, showed an intrinsic foundation that ensure its adaptation to the warmer Great Lakes and farther south, especially in functional terms like “Cul4-RING E3 ubiquitin ligase complex.” Meanwhile, the specific 78 fast-evolving genes and 41 positively selected genes in S. lucioperca drew a clear picture of how it evolved to a large and elongated body with camera-type eyes and muscle strength so that it could occupy the highest position in the food web. Overall, our results uncover genetic basis that support evolutionary adaptation of temperature and body shape in four Percid species, and could furthermore assist studies on environmental adaptation in fishes.

Summary Temporal variation in reproductive traits of geographically distributed fish is supposed to take place in response to the spatial and environmental variations. With regard to the wide distribution of the European perch in the northern hemisphere, important reproductive traits such as the initiation and duration of the spawning activity are likely to vary in different latitudinal gradients. In this study, reproductive biology of the European perch, Perca fluviatilis, is described, based on 324 specimens caught in the Anzali wetland (southwest Caspian Sea) between June 2008 and May 2009. The gonadosomatic index, oocyte frequency distribution and histological examination suggested a long vitellogenic process (October to February) and a short spawning season (January and February). The size-frequency distribution of the oocytes showed that this perch is a species with group-synchronous ovarian development. Ovarian development occurred only in one clutch of oocytes (700–900 μm oocyte diameter) with no indication of maturation of any subsequent clutch in the spawning season. The average of (realized) fecundity (±SD) was estimated to be 16177 ± 5846 eggs in late vitellogenic stage, which was lower than the potential fecundity (17188 ± 6917 eggs). Histological examination of the gonads revealed the existence of atretic oocytes in early vitellogenic stages (October and November). This investigation highlights the temporal variation in the initiation and duration of the reproductive activity of the European perch in this region compared to other geographical regions. The results emphasize the necessity of specific temporal management in fishing of European perch based on spatial differences in reproductive biology.

The basin of Lake Baikal is the southeastern boundary of the native area of perch Perca fluviatilis, widely distributed in Eurasia. Perch was introduced into Lake Kenon (basin of the Amur River) from Lake Ivan (basin of the Lena River) in 1920. Complete restructuring of the fauna of parasites of the host 90 years after the perch invasion is revealed. The restructuring is typical of introduced fishes: the disappearance of mother fauna of parasites and the acquisition of new species. Parasitological data show the separation of the perch population of Lake Kenon into two groups: “western” and “eastern.”

This study examined embryo survival and viability of Eurasian perch, Perca fluviatilis L., larvae in relation to the fragmentation of oil droplets in ovulated oocytes. The study was conducted after controlled reproduction. Four (I–IV) categories of egg-ribbons quality were distinguished, based on the degree of oil droplet fragmentation (where at least one oil droplet with minimum 0.39 mm diameter were certified in all oocytes in egg-ribbon — categories I and II) and percentage of eggs with highly fragmented oil droplets (where diameter of oil droplets did not exceed 0.35 mm — categories III and IV) in the egg-ribbon. The dynamics of survival and some morphological parameters were investigated during embryonic and larval development up to 10 days post-hatch (DPH), under laboratory conditions. The laboratory-obtained results were compared to semi-commercial incubation and initial larval rearing. The fragmentation of oil droplets was accompanied by a decrease in egg quality. Oil droplets were found to coalesce after activation of eggs in water and during incubation process. Thus, the presented categorization may be used in non-activated eggs only. In both experiments, at 10 DPH the percentages of feeding larvae and those with an inflated swim bladder were recorded. The best results of laboratory-conducted incubation were obtained in category I and II (92.80 and 74.20% in the eyed-egg stage respectively). In category IV, the mortality rate of embryos exceeded 90%. The highest body deformation rate of freshly hatched larvae was observed in category III (67.86%) and IV (86.14%) that was related with fragmentation of oil droplets. These results were confirmed under semi-commercial conditions. The obtained results indicate that the proposed categorization may be a valuable tool for the quality evaluation of Eurasian perch egg-ribbons. It could be successfully applied in both commercial fish production and scientific activity.

The host range of ranaviruses was investigated by challenging pike-perch (Sander lucioperca) with the following ranavirus isolates: epizootic haematopoietic necrosis virus (EHNV), European sheatfish virus (ESV), European catfish virus (ECV), pike-perch iridovirus (PPIV), short-finned eel virus (SERV) and frog virus 3 (FV3). Pike-perch fry were bath-challenged at 12 °C and 22 °C at 5 weeks post hatching, and the challenge was repeated with EHNV and PPIV in older fish (15 weeks post hatching) at higher densities. A third batch of fish was subjected to intraperitoneal (i.p.) and cohabitation challenge with EHNV, ESV, ECV and PPIV at 16 °C. Statistically significant mortality was observed in EHNV-challenged fish at both temperatures in the five week old fish. No mortalities were seen in older fish challenged with EHNV and PPIV. High mortalities were registered in i.p.-challenged fish, but not in cohabitated fish. Virus re-isolation was possible from the youngest bath-challenged fish in all challenge trials and the i.p.-challenged fish, but not from older fish or cohabitated fish. Susceptibility of pike-perch to ranaviruses appears to be dependent on age of fish and challenge route. The study shows that pike-perch are susceptible to infection with ranavirus under certain conditions, and it is suggested that this be considered when reviewing the legislation on notifiable diseases.

The turnover and distribution of energy and nutrients in food webs is influenced by consumer stoichiometry. Although the stoichiometry of heterotrophs is generally considered to vary only little, t ...