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This study presents a large-scale interlaboratory comparison (ILC) aimed at detecting and quantifying DNA from two European anglerfish (Lophius budegassa, Lophius piscatorius), pike (Esox lucius) and sea bream (Spondyliosoma cantharus) using real-time qPCR. To detect amplification of the parvalbumin genetic marker, single and multiplex qPCR assays using EvaGreen® dye or TaqMan™ probes were used. Genomic DNA isolated from target fish species and an advanced DNA calibrator, gBlocks® gene fragments, were used as standards. The DNA of anglerfish, pike and sea bream as well as their mixtures were analysed together with 14 other non-target fish species. All target fish samples were correctly identified by the participating laboratories. Qualitative assessment of anglerfish and seabream DNA showed an accuracy rate of 100%, while pike DNA achieved a match rate of 99%. Validation of quantitative protocols in four different laboratories consistently achieved z-scores below 2, indicating satisfactory performance and confirming the high degree of similarity of laboratory results. Furthermore, high accuracy and efficiency were demonstrated for the quantification of anglerfish and seabream DNA by triplex qPCR using TaqMan™ probes. Regarding the selected gene marker, the major fish allergenic protein parvalbumin enables indirect detection and quantification of the allergen in the sample. Therefore, the use of proposed protocols can significantly contribute to protecting the health of consumers and to controlling the food market. [ABSTRACT FROM AUTHOR]

Background: The genus Nematostrigea comprises trematodes parasitising in fish-eating birds of Europe, Africa, and North America. Their life cycle is unknown. Purpose: To provide the first description of metacercariae of Nematostrigea serpens serpens, a nominative subspecies of the type species of Nematostrigea, and to record metacercaria of Nematostrigea vietnamiensis, with molecular data. Methods: Encysted metacercariae of N. serpens serpens and N. vietnamiensis were collected from fish in Russia and Vietnam, respectively, and were processed, identified, and documented using standard morphological techniques. The 28S rRNA gene of metacercariae of both species and the cox1 gene of metacercariae an earlier studied adult of N. serpens serpens were sequenced and used for phylogenetic analysis. Results: Metacercaria of N. serpens serpens have a spatulate body with a foliate forebody and a short hindbody, two long lateral rectilinear pseudosuckers, and the holdfast organ with bifurcated anterior and entire posterior external lobes. The analysis of the cox1and 28S rRNA gene sequences unequivocally showed the conspecificity of metacercariae and adult stage of N. serpens serpens. Based on the 28S rRNA gene sequence-based phylogenetic analysis, the genus Nematostrigea is a sister taxon to the group of strigeid genera Cotylurus + Ichthyocotylurus. Morphological and phylogenetic data demonstrated that N. vietnamiensis does not belong to the genus Nematostrigea and is possibly be affiliated with the crassiphialine trematodes. Conclusion: This is the first record of metacercariae of N. serpens serpens. N. vietnamiensis, renamed Prodiplostomulum vietnamiense comb. nov., must be moved to the crassiphialine 'Prodiplostomulum'-type metacercariae group [ABSTRACT FROM AUTHOR]

This study investigated the effects of a six-week starvation period on the fatty acid profile, body composition and blood parameters of intensively reared pike (Esox lucius). 150 pike were stocked in an experimental recirculating aquaculture system (RAS) and feed was completely withdrawn. Body composition, fatty acid composition and blood parameters (serum protein, albumin, triacylglycerol, cholesterol concentration and Lactate dehidrigenase and alkaline phosphatase activity) were measured and somatic indices were calculated. A significant decline in bodyweight, crude fat content and somatic indices was accompanied by a significant decrease of blood triacylglycerol content. The relative proportion of saturated fatty acids in the fillet decreased, while polyunsaturated fatty acids increased. There was also a significant increase in the average chain length and unsaturation index of fatty acids found in the fillet flesh. [ABSTRACT FROM AUTHOR]

Intraspecific genetic admixture occurs when previously separated populations within a species start interbreeding, and it can have either positive, negative, or neutral effects on reproductive performance. As there currently is no reliable predictor for the outcome of admixture, an increased knowledge about admixture effects in different species and populations is important to increase the understanding about what determines the response to admixture. We tested for effects of admixture on F1 offspring quality in three subpopulations of pike (Esox lucius). Gametes were collected in the field, and eggs from each female were experimentally fertilized with milt from a male from each population (one "pure" and two "admixed" treatments). Three offspring quality measures (hatching success, fry survival, and fry length) were determined and compared between (a) pure and admixed population combinations and (b) the sex‐specific treatments within each admixed population combination (based on the origin of the male and female, respectively). The results suggested that although there were no overall effects of admixture on offspring quality, the consequences for a given population combination could be sex‐specific and thus differ depending on which of the parents originated from one or the other population. All offspring quality traits were influenced by both maternal ID and paternal ID. Sex‐ and individual‐specific effects can have implications for dispersal behavior and gene flow between natural populations, and are important to consider in conservation efforts. We tested for effects of genetic admixture on offspring quality in three natural subpopulations of pike (Esox lucius) in an artificial fertilization experiment with a common garden setup. The results revealed that although there were no overall effects on offspring quality on the population level, the effects for a given combination of populations could differ depending on which of the parents originated from one or the other population. Such sex‐specific effects have implications for dispersal behavior and gene flow between natural populations, and are important to consider in conservation efforts. [ABSTRACT FROM AUTHOR]

An environmental study of pike Esox lucius recorded their presence in 522 Irish lakes and that they coexisted with brown trout Salmo trutta in 97 of these. Statistical models, accounting for spatial non‐independence among lakes, suggested that lakes with greater area, maximum depth and stream connectivity show a higher probability of coexistence. Introductions of E. lucius are likely to have negative effects on S. trutta stocks in small isolated lakes, but coexistence may be possible in larger systems. [ABSTRACT FROM AUTHOR]

Variation in movement between individuals can have important ecological effects on populations and ecosystems, yet the factors driving differences in movement and their consequences remain poorly understood. Here, individual variability in the movements of juvenile (age 0 + and 1 + year) pike Esox lucius was assessed using passive integrated transponder ( PIT) telemetry in off-channel nursery areas over a 26- month period. Differences in the movement patterns of individuals were tested against their body sizes, ages, growth rates and trophic positions using data collected through a combination of catch-and-release sampling and stable isotope analyses. Results revealed that variation in movement between individuals was affected by age, with 1 + individuals moving more than individuals of age 0 + , but not length. Individuals whose TP was low on their initial capture event moved significantly less than those with a higher initial TP. Individuals that moved more grew faster and achieved a higher final TP. These results suggest that higher activity (i.e., increased movement) increases resource acquisition that enhances growth rates, which could ultimately maximise individual performances. [ABSTRACT FROM AUTHOR]

Esox flaviae represents the native esocid species of the Italian peninsula at present potentially highly threatened by the diffusion of exotic E. lucius. Here, we present a novel mtDNA ( N = 272) and microsatellite ( N = 275) dataset including 13 test and 3 reference samples, aimed to delineate the distribution of the native as well as the exotic species and to unravel potential introgressive hybridisation between the two species in Northern Italy. We highlight a complex mosaic distribution of both species, with contrasting occurrence even between neighbouring sites. Significant genetic substructure is still observed within E. flaviae, while the dispersal of the invader seems to be promoted by restocking actions. In addition, we prove the existence of introgressive hybridisation between native and exotic pikes. Here, gender-biased hybridisation is suggested, with native E. flaviae constituting the predominant 'mother species' in the hybridisation process. Finally, we underline the need for a revision of fisheries management regulations, for which a nation-wide and exhaustive genetic screening in the near future should build the scientific basis. [ABSTRACT FROM AUTHOR]

Predation is thought to be one of the main structuring forces in animal communities. However, selective predation is often measured on isolated traits in response to a single predatory species, but only rarely are selective forces on several traits quantified or even compared between different predators naturally occurring in the same system. In the present study, we therefore measured behavioral and morphological traits in young-of-the-year Eurasian perch Perca fluviatilis and compared their selective values in response to the 2 most common predators, adult perch and pike Esox lucius. Using mixed effects models and model averaging to analyze our data, we quantified and compared the selectivity of the 2 predators on the different morphological and behavioral traits. We found that selection on the behavioral traits was higher than on morphological traits and perch predators preyed overall more selectively than pike predators. Pike tended to positively select shallow bodied and nonvigilant individuals (i.e. individuals not performing predator inspection). In contrast, perch predators selected mainly for bolder juvenile perch (i.e. individuals spending more time in the open, more active), which was most important. Our results are to the best of our knowledge the first that analyzed behavioral and morphological adaptations of juvenile perch facing 2 different predation strategies. We found that relative specific predation intensity for the divergent traits differed between the predators, providing some additional ideas why juvenile perch display such a high degree of phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accelerometer technology was used to evaluate behaviours in the teleost ambush predator pike Esox lucius foraging on crucian carp Carassius carassius. Automated rule-based estimates of prey-size determined handling time were obtained and are compared with video-recorded behaviours. Solutions to tag attachment and the limitations imposed by battery-time and data-logging capacities are evaluated. [ABSTRACT FROM AUTHOR]

Background: Pikes represent an important genus (Esox) harbouring a pre-duplication karyotype (2n = 2x = 50) of economically important salmonid pseudopolyploids. Here, we have characterized the 5S ribosomal RNA genes (rDNA) in Esox lucius and its closely related E. cisalpinus using cytogenetic, molecular and genomic approaches. Intragenomic homogeneity and copy number estimation was carried out using Illumina reads. The higher-order structure of rDNA arrays was investigated by the analysis of long PacBio reads. Position of loci on chromosomes was determined by FISH. DNA methylation was analysed by methylation-sensitive restriction enzymes. Results: The 5S rDNA loci occupy exclusively (peri)centromeric regions on 30-38 acrocentric chromosomes in both E. lucius and E. cisalpinus. The large number of loci is accompanied by extreme amplification of genes (>20,000 copies), which is to the best of our knowledge one of the highest copy number of rRNA genes in animals ever reported. Conserved secondary structures of predicted 5S rRNAs indicate that most of the amplified genes are potentially functional. Only few SNPs were found in genic regions indicating their high homogeneity while intergenic spacers were more heterogeneous and several families were identified. Analysis of 10-30 kb-long molecules sequenced by the PacBio technology (containing about 40% of total 5S rDNA) revealed that the vast majority (96%) of genes are organised in large several kilobase-long blocks. Dispersed genes or short tandems were less common (4%). The adjacent 5S blocks were directly linked, separated by intervening DNA and even inverted. The 5S units differing in the intergenic spacers formed both homogeneous and heterogeneous (mixed) blocks indicating variable degree of homogenisation between the loci. Both E. lucius and E. cisalpinus 5S rDNA was heavily methylated at CG dinucleotides. Conclusions: Extreme amplification of 5S rRNA genes in the Esox genome occurred in the absence of significant pseudogenisation suggesting its recent origin and/or intensive homogenisation processes. The dense methylation of units indicates that powerful epigenetic mechanisms have evolved in this group of fish to silence amplified genes. We discuss how the higher-order repeat structures impact on homogenisation of 5S rDNA in the genome. [ABSTRACT FROM AUTHOR]

The objective of the research was to test the effect of iron and aluminium coagulants commonly used for lake re-cultivation, on the pike sperm motility and fertilisation. The coagulants caused changes in the analyzed hydrochemical parameters of the water such as: Fe, Mg2+, TSS, SO42- and Cl-. Selected parameters of sperm motility: MOT, VCL, VSL, VAP, LIN were estimated using CASA. The sperm motility at the moment of activation was the highest in the control sample. With increasing the time of exposure the proportion of sperm motility in the analyzed semen decreased. In the samples with coagulants the values of MOT, VCL and VSL were smaller than in the control sample (statistically significant differences between the control and the samples with PIX and PAX were recorded in the 25th-30th second after activation). The percentage of fertilised eggs was the greatest in the control sample and in the PAX®18 sample (73.11 and 70.42%, respectively), whereas in the PIX®113 it was less than that (54.88%). The shortest larvae were those in the sample with coagulant PIX®113. In the samples with PIX®113 and PAX®18 the survivorship of embryos compared to the control sample was the smallest (43.10 and 51.61%, respectively and control 67.60%) and the proportion of malformed larvae was the highest (34.82 and 24.52%, respectively and control 15.17%). [ABSTRACT FROM AUTHOR]

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The fish genus Esox (Teleostei, Esocidae) has been recorded from thirty late Miocene, Pliocene, and Pleistocene localities where forty-one bone-bearing strata are exposed in the territory of Ukraine, Russian Federation, and Republic of Moldova. From eight localities the genus is reported or described for the first time. A detailed description and morphological analysis of the currently available osteological material demonstrates the presence of four species in the studied area: (i) Esox sibiricus (late Miocene-early Pliocene); (ii) Esox moldavicus (early Pliocene-early Pleistocene); (iii) Esox nogaicus sp. nov. (early Pleistocene, Calabrian); (iv) Esox lucius (early-middle Pleistocene). The Northern Pike (Esox lucius) is recorded for the first time in the early Pleistocene fossil record of southeastern Europe. The new species E. nogaicus is characterized by a massive dentary with deep symphysis and the possible presence of a pair of fixed canine-like teeth near the anterior end of the vomer. Such canine teeth are seen also in certain species known only from North America, the extant Esox masquinongy, the fossil species E. columbianus, and an unnamed Miocene form. However, unlike in E. nogaicus, in the three North American species fixed canines also occur anteriorly on the palatines. The Miocene, Pliocene, and Pleistocene pikes from southeastern Europe document a greater diversity of morphologies in the past than exists today in the pike species of Europe. Changes in the predominant species of Esox in southeastern Europe are hypothesized to be driven by changing global and regional climates. [ABSTRACT FROM AUTHOR]

The fish genus Esox (Teleostei, Esocidae) has been recorded from thirty late Miocene, Pliocene, and Pleistocene localities where forty-one bone-bearing strata are exposed in the territory of Ukraine, Russian Federation, and Republic of Moldova. From eight localities the genus is reported or described for the first time. A detailed description and morphological analysis of the currently available osteological material demonstrates the presence of four species in the studied area: (i) Esox sibiricus (late Miocene-early Pliocene); (ii) Esox moldavicus (early Pliocene-early Pleistocene); (iii) Esox nogaicus sp. nov. (early Pleistocene, Calabrian); (iv) Esox lucius (early-middle Pleistocene). The Northern Pike (Esox lucius) is recorded for the first time in the early Pleistocene fossil record of southeastern Europe. The new species E. nogaicus is characterized by a massive dentary with deep symphysis and the possible presence of a pair of fixed canine-like teeth near the anterior end of the vomer. Such canine teeth are seen also in certain species known only from North America, the extant Esox masquinongy, the fossil species E. columbianus, and an unnamed Miocene form. However, unlike in E. nogaicus, in the three North American species fixed canines also occur anteriorly on the palatines. The Miocene, Pliocene, and Pleistocene pikes from southeastern Europe document a greater diversity of morphologies in the past than exists today in the pike species of Europe. Changes in the predominant species of Esox in southeastern Europe are hypothesized to be driven by changing global and regional climates. [ABSTRACT FROM AUTHOR]

Pike in the western Baltic Sea live on the edge of their salinity tolerance. Under physiologically challenging conditions, organism may respond by moving to environmentally more benign areas during critical periods, such as during spawning. We hypothesised that pike in a brackish lagoon (8-10 ppt salinity) would perform spawning- and feeding-related movements between areas with different salinity regimes. Twenty-two pike were caught prior to spawning, tagged with acoustic transmitters, and their movements were tracked for 18 months. Pike showed two main patterns of movements that were consistent within individuals across two years. Whereas some individuals stayed in the lagoon year-round, most pike left the lagoon for longer periods after spawning and returned to the lagoon prior to following year's spawning season. We found no evidence that probability of moving out of the lagoon co-varied with either length or condition factor. Despite the fact that the lagoon's salinity is close to the reported upper limit for pike egg development, results indicated that all pike spawned in the lagoon. Correspondingly, genetic data showed that all fish belonged to the same reproductive population unit. Movement patterns thus appear to reflect individual variation in home-range and/or resource optimisation following ideal free principles. [ABSTRACT FROM AUTHOR]

Eutrophication of lakes has increased the risk of fish kills during winter under ice cover. If such a lake is isolated, the fish assemblage consists of only oxygen-tolerant species without predatory species. Here, our main aim was to analyze the fate of 99 marked pike (Esox lucius) stocked to a pikeless lake that is known to have low oxygen concentrations under ice cover. These pike (total lengths 33.5–76.9 cm; weights 260–3050 g) were stocked in May 2008 and were followed 7 years. The first marked pike was caught in August 2008 and the last one in September 2012. Between these dates, 21 pike were caught at least once, five pike were caught twice, and two pike were caught three times. Relative condition was based on the length–weight relationship. Both length and weight affected significantly the recapture probability, whereas relative condition had no effect. The growth of marked pike was estimated based on length or weight increments in two separate models with either starting length or weight together with the number of days between observations. In these models, the number of days had positive, and size, either length or weight, had a negative relationship with growth. According to marginalr2, length and the number of days explained 65.5% of variation in length increments, whereas the marginalr2for weight and the number of days was 49.3% for weight increments. The length increment model was used to compare pike growth in Lake Savijärvi with other Finnish lakes. The comparison showed that during the first four growing seasons after stocking, the pike growth in Lake Savijärvi was faster than in the other lakes studied. [ABSTRACT FROM PUBLISHER]

In 2005 and 2006, the United States Army Corps of Engineers released experimental flows to mimic natural spring flooding on the highly regulated lower Savannah River in the Southeastern US. We used vegetation, invertebrate, and fish communities to assess how past regulation and current experimental releases were affecting the ecological conditions on floodplains. The nearby Altamaha River, of similar size but retaining near-natural spring pulses, served as a reference. We did not find that past flow regulation of the Savannah River had significantly altered floodplain forest structure. However, numbers of tree seedlings in bottomland hardwood forests were higher during a year with an artificial pulse than one without. Analyses of invertebrate and fish communities suggested some limited differences in floodplain community structure between rivers, with differences being most pronounced for predaceous Dytiscidae beetles and Esox spp. fishes. Artificial re-creation of small spring flood pulses down the Savannah River in 2005 and 2006 elicited some responses from fish and invertebrates, but did not shift species assemblages towards those occurring on Altamaha River floodplains. [ABSTRACT FROM AUTHOR]

This study tested for links among behaviour, state and life-history variables as predicted by the pace-of-life hypothesis in adult pike Esox lucius. First, a standardized open-field behavioural assay was developed to assess individual behaviour of wild-captured adult E. lucius. Behaviour within the standardized assay predicted swimming behaviour in the lake, providing an ecological validation of the assay. There was no relationship between standardized behaviour and any of the life-history and state variables, including metabolism, body condition, juvenile growth rate and adult growth rate in contrast to predictions from the pace-of-life hypothesis. This study demonstrates that it is possible to assess ecologically relevant behavioural variation in a large-bodied top predator using a standard open-field assay, but it is noteworthy that this standardized behaviour is not systematically related to standard metabolism or growth. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the impact pike fishing season (before spawning in fall (group A) and after spawning in spring (group B)) had on the slaughter yield and fillet fatty acid profile. The slaughter yield of fillets with skin and skinned fillets from the group B fish was significantly lower (by approximately 7.5% of body weight). The fatty acid profile of the fish meat from the groups examined differed significantly. The fillets of pike caught before spawning were dominated by unsaturated fatty acids (UFA), while those from fish caught after spawning had mainly saturated fatty acids (SFA). The share of polyunsaturated fatty acids (PUFA) in the fillets of fish that had spawned was sixfold lower, and the n-3 PUFA differences were nearly ninefold. The content of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids in fillets of fish that had spawned was ninefold lower than in those that had not yet done so. Consequently, the ratio of n-3 PUFA/n-6 PUFA in pike from group A was over three times higher than that in the fish that had spawned (2.61 vs 0.82). Fillets from pike that have spawned are a significantly poorer source of valuable fatty acids for consumers. [ABSTRACT FROM AUTHOR]

Half a century after introducing the final host Northern pike (Esox lucius L. 1758) into Lake Grundlsee in Austria, a sudden massive infection with the pike tapeworm Triaenophorus crassus Forel 1868 was noticed in the population of the intermediate host Arctic charr (Salvelinus umbla (L. 1758)) and led to the closure of this famous fishery. In an effort to contain the epidemic, a total of 1163 pike were removed over a period of three years (2008-2010). The efficiencies of gill and fyke netting as well as electro and spear fishing were assessed. All four methodswere costlywithEUR37-371 to catch a single fish. During intensive fishing, catch per unit effortandfishlengthsof pikedeclined. Fyke netting coupled with electro fishing turnedout to be the most practicable strategy to reduce the pike stock. After another three years, prevalence of T. crassus in Arctic charr could be reduced by 40% in 2013. However, it will be impossible to completely eradicate pike and its parasite in the lake. [ABSTRACT FROM AUTHOR]

The first comprehensive investigation of pike Esox lucius trophic ecology in a region (Ireland) where they have long been thought to be a non-native species is presented. Diet was investigated across habitat types (lake, river and canal) through the combined methods of stable-isotope and stomach content analyses. Variations in niche size, specialization and the timing of the ontogenetic dietary switch were examined, revealing pronounced opportunism and feeding plasticity in E. lucius, along with a high occurrence of invertivory (up to 60 cm fork length, LF) and a concomitant delayed switch to piscivory. Furthermore, E. lucius were found to primarily prey upon the highly available non-native roach Rutilus rutilus, which may alleviate predation pressure on brown trout Salmo trutta, highlighting the complexity of dynamic systems and the essential role of research in informing effective management. [ABSTRACT FROM AUTHOR]

The lysosomal enzyme activities of the cestode Triaenophorus nodulosus and its host, the pike, in aquatic bodies with different degrees of technogenic transformation (Northern Karelia, Russia) have been studied. As has been shown, iron-ore waste causes an increase in the acid phosphatase, nuclease, and β-galactosidase activities of the host and a decrease in its β-glucosidase and cathepsin D activities. As a rule, the changes in the same cestode enzyme activities are the opposite. With a decrease in the technogenic load, most of the studied characteristics display the trend of approaching the corresponding values observed in a clean lake. It is assumed that the host plays a leading role in the biochemical adaptation of the parasite and its host to mineral environmental pollution. [ABSTRACT FROM AUTHOR]

Copyright of Cybium: International Journal of Ichthyology is the property of Societe Francaise d'Ichtyologie (SFI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A recent publication (Pedreschi et al., 2014, Journal of Biogeography, 41, 548-560) casts doubt over the status of pike (Esox lucius) as a non-native species in Ireland by reporting two distinct genetic groups of pike present: one a human introduction in the Middle Ages, the other hypothesized to result from natural colonization after the Last Glacial Maximum (LGM). While the existence of two groups is not disputed, the hypothesized natural colonization scenario conflicts with the sequence in which the islands of Britain and Ireland became isolated from Europe after the LGM. An alternative natural colonization scenario raised herein was rejected, leaving an earlier, two-phase, human introduction of pike from Britain or Europe to Ireland as a realistic alternative hypothesis explaining the results of Pedreschi et al. (2014). This leaves the debates on human introduction versus natural colonization, introduced versus native species status, and pike management in Ireland wide open. [ABSTRACT FROM AUTHOR]

Length-weight relationships for Alburnus arborella, Esox cisalpinus and Scardinius hesperidicus from Trasimeno Lake are provided. A total of 4,205 specimens were collected for examination from 2008 to 2014 throughout the lake by means of electrofishing and nets. For all species the value of b ranged from 2.887 for Esox cisalpinus males to 3.115 for Scardinius hesperidicus. The study provides the first reference of length-weight relationships for the three species. A new maximum total length is also reported for E. cisalpinus. [ABSTRACT FROM AUTHOR]

Background Freshwater fishes of the genus Esox are found throughout the Holarctic region. The northern pike (E. lucius) has a circumpolar distribution whereas the assumed sister species the Amur pike (E. reichertii) is only found in the Amur region. The genetic structure and post-glacial dispersal of these species are not well known. Here, we use sequence variation at two mitochondrial DNA regions (cytb and D-loop) to investigate the phylogeography, infer location of glacial refugia and investigate the time of divergence and potential demographic expansion of the various clades detected. Results The two species did not share haplotypes implying long-term isolation with no gene flow, and divergence of the taxa were estimated at 4.55 Myr. The northern pike mtDNA haplotypes revealed three main lineages. One of the northern pike mtDNA lineages was found throughout the entire Holarctic region suggesting transcontinental dispersal from a single refugium. The three lineages exhibited a star phylogeny, indicating population expansion following isolation in separate glacial refugia. Estimated time of divergence of these lineages was 0.18 - 0.26 Myr. Conclusions The precise location of the glacial refugia is uncertain, but our data suggests an Asian origin. The expansion of the circumpolar lineage is estimated to be around the end of the second glacial, implying that the current distribution is due to a recent recolonization from an east- Asian refugium. All three northern pike mtDNA lineages occurred sympatrically in Europe, possibly due to secondary contact. Two of the lineages probably originated from different European refugia, one in the Danube-region and one in Western Europe, the latter seems to be the primary source for recolonization of northern Europe. [ABSTRACT FROM AUTHOR]

Copyright of Natura Croatica is the property of Natura Croatica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The relationship between total length ( L, cm) and weight ( W, kg) in the large northern pike ( Esox lucius) was investigated using a dataset comprising 802 specimens weighing between 1 and 18.8 kg caught during fishing competitions. The applying the data to the equation W = aLb , yielded a = 6.648 × 10-6 and b = 3.0217. Weight residuals fluctuate during the fishing season, likely due to conditions of the fish, probably associated with gonad development. Additionally, the equations including maximum girth ( G, cm) - W = aGb and W = a( L × G) b - were fitted using a subset of record fish totalling 186 specimens. Comparison of the equations W = aLb and W = aGb showed that weight was better described by maximum girth (AIC = 624.9) rather than by length (AIC = 690.0), but the best fit was obtained with the equation W = a( L × G) b (AIC = 566.3) with the parameters a = 2.426 × 10-3 and b = 0.974. [ABSTRACT FROM AUTHOR]

Large numbers of microsatellite loci for many species are increasingly made available from public data bases or through de novo isolation with next generation sequencing methods. However, the challenge remains to identify the subset of loci with suitable polymorphism for the populations of interest. This normally requires genotyping individuals in a representative subset of populations., Here, we present an approach that does not require individual genotypes, but instead uses the presence and absence of alleles in pooled DNA samples to estimate within-population variation ( WPV, i.e. polymorphism) and among-population variability ( APV, i.e. rare alleles). From these, we developed a scoring procedure to rank individual loci and thereby identify those most suitable for individual genotyping., We used multiplex PCR of 20 pooled individuals from each of 12 populations to screen a total of 80 published and unpublished microsatellite loci in the Northern pike Esox lucius, a species known to exhibit low genetic variability, thus predisposing it as a model species to test our approach. The screening of pooled samples revealed extremely different levels of microsatellite variability, ranging from 1·0 to 27·5 alleles per microsatellite ( WPV) and from 1·4 to 12 populations per allele ( APV). Scoring placed microsatellites with high WPV and medium APV at the highest ranks., We validated this outcome by genotyping individuals of two pike populations from geographically close areas. A strong differentiation potential (measured as Weir's & Cockerham's FST) as well as a better resolving power of higher over lower-ranked microsatellites (measured as Nei′s DA and probability of identity) proved that the method presented here is suitable for rapid and inexpensive identification of appropriate microsatellites without a priori knowledge of genotypes., Our scoring procedure is generally applicable to all population genetic studies based on microsatellites and is particularly recommended, if species with low genetic variability are to be investigated. [ABSTRACT FROM AUTHOR]

This study examined effects of varying concentrations of the environmental contaminant perchlorate in northern pike (Esox lucius) based on exposure in water and/or from prey (threespine stickleback,Gasterosteus aculeatus). Routes of exposure to pike were through contaminated water at 0, 10, or 100 mg/L perchlorate for 49 d and/or through feeding, 1 per day over 14 d, sticklebacks that were previously maintained in water at 0, 10, or 100 mg/L perchlorate. Both water and food significantly contributed to pike tissue concentrations of perchlorate as compared to controls, but, as expected for a water-soluble contaminant, perchlorate did not biomagnify from prey to predatory fish. Pike gastrointestinal tissue retained significantly more perchlorate than other tissues combined. Route of exposure and concentration of perchlorate in various media are important to consider in risk assessment when evaluating uptake and tissue concentration of perchlorate because significantly higher tissue concentrations may result from combined prey and water exposures than from prey or water exposures alone in a concentration-dependent manner. [ABSTRACT FROM PUBLISHER]

A new species of fish leech from Poland, Piscicola burresoni n. sp. (Piscicolidae), is described. The leech was found in 2007 on stones and on pike (Esox lucius L.) and chub (Leuciscus cephalus L.) in the Łyna River, Poland. The leech is small, relatively flattened, with a prominent coarctation between the trachelosome and urosome. The pigmentation is unique to the new species and it has 14 annuli with gonopores separated by 4 annuli. The receptaculum seminis consists of an elliptical aperture located at a distance of 3 annuli behind the female gonopore. The copulatory area on the clitellum is characteristic in the shape of a parallel ellipse. The vector tissue is in the form of a transverse plate below the oviduct outlet. For a complete description of the external morphology, a geometric- mathematical model of the leech body form was used. [ABSTRACT FROM AUTHOR]

For circumpolar species, little is known on how somatic growth rates can vary at large, transcontinental spatial scales. In this study, a meta-analysis of growth rates was conducted for northern pike ( Esox lucius) across North America and Eurasia. Growth rates of northern pike did not differ between North American and 'coastal Eurasian' pike (e.g., UK, Ireland, Sweden), while growth rates for both of these groups were significantly higher compared to 'inland Eurasian' pike (mainly in Russia). There was no difference in growth between lentic and lotic habitats on either continent. In North America, pike growth was positively correlated with temperature, but in Eurasia, pike growth correlated poorly with most climatic variables. Similarly, maximum longevity in pike populations was significantly predicted by latitude in North America, but not in Eurasia. After standardising annual pike growth by the thermal opportunity for growth, a highly significant countergradient growth relationship was found for North American pike, while a significant, but considerably less predictive countergradient growth relationship was found for Eurasian pike. This study provides novel insights into the ecology of a circumpolar species and how populations function at extraordinarily large spatial scales. First, pike appear to be cosmopolitan across hydrologic habitats having fast or slow growth in either lentic or lotic environments. Secondly, continental-scale differences in pike growth rates are suggestive of major genetic and life-history differences. Finally, variable climate-growth relationships and countergradient growth patterns indicate that global climate change is likely to affect circumpolar fishes like pike in complex, nonlinear ways. [ABSTRACT FROM AUTHOR]

- Temperate lakes can be ice covered for several months each year, yet little is known about the behaviour and activity of the fish during the cold season. As northern pike represents the top of the food web in many northern temperate lakes and may structure the ecosystem both directly and indirectly, a detailed understanding of the behaviour of this species during winter is important. We continuously monitored the activity of adult northern pike ( Esox lucius) in a small temperate lake from late summer to winter for two consecutive years using an automatic acoustic positional telemetry system. Four subsample periods representing different temperature regimes from each year were chosen for further investigation. The results revealed that pike activity was similar between seasons. In all periods, a distinct diel pattern, showing increased activity during day as compared to night, was evident. Our findings indicate that the fish component of temperate lentic ecosystems can be more active during the cold season than previously assumed. This may have implications for the structuring effect of pike on the lower trophic levels. [ABSTRACT FROM AUTHOR]

Pike Esox lucius in the absence of prey and conspecifics were shown to have the highest habitat-change activity during dusk and to decrease preference for complex habitats in turbid water. As the behaviours indicate routine responses in the absence of behavioural interactions, E. lucius spatio-temporal distributions should be directly affected and thereby more easily assessed and avoided by prey, with potential consequences for encounter rates. [ABSTRACT FROM AUTHOR]

This study investigated the movement patterns of Baltic Sea pike Esox lucius in Matsalu Bay, Estonia, using otolith microchemistry. Migration patterns of E. lucius were remarkably diverse, but distinct groups were evident. Of the E. lucius analysed ( n = 28), 82% hatched in fresh water and 74% of them left this biotope during the first growth season. [ABSTRACT FROM AUTHOR]

We address the taxonomic position of the southern European individuals of pike, performing a series of tests and comparisons from morphology, DNA taxonomy and population genetics parameters, in order to support the hypothesis that two species of pike, and not only one, exist in Europe. A strong relationship emerged between a northern genotype supported by COI, Cytb, AFLP and specific fragments, and a phenotype with round spot skin colour pattern and a large number of scales in the lateral line, clearly separated from a southern genotype with other skin colour pattern and a low number of scales in the lateral line. DNA taxonomy, based on a coalescent approach (GMYC) from phylogenetic reconstructions on COI and Cytb together with AFLP admixture analysis, supported the existence of two independently evolving entities. Such differences are not simply due to geographic distances, as northern European samples are more similar to Canadian and Chinese samples than the southern Europe ones. Thus, given that the differences between the two groups of European pike are significant at the phenotypic, genotypic and geographical levels, we propose the identification of two pike species: the already known northern pike (Esox lucius) and the southern pike (E. flaviae n.sp.). The correct identification of these two lineages as independent species should give rise to a ban on the introduction of northern pikes in southern Europe for recreational fishing, due to potential problems of hybridisation. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the growth rate and growth parameters of pike Esox lucius L. in the mesotrophic Lake Rubikiai and to evaluate species growth in light of environmental conditions in Lithuanian lakes of different limnologic types. A total of 204 pike specimens were caught in two subsequent years, April 2005 and April 2006, in Lake Rubikiai. Six age classes (2-7 years of age) for males and 10 age classes (3-12 years of age) for females were identified by scale readings; 2- to 4-year-old males and 4- to 7-year-old females prevailed. Total length of pike ranged from 26.5 to 107 cm and weight from 106 to 7600 g. There were no statistically significant differences (Student's t-test, P > 0.1) between mean lengths and weights of males and females of the same age. Von Bertalanffy growth parameters for the entire population were: L = 131.7 cm, k = 0.1530 year, t = −0.0398 year. Calculated overall growth performance index ϕ′ was 3.42. The length-weight relationship was described by the equation . The growth rate of pike in Lake Rubikiai was higher than in most other investigated Lithuanian lakes. Pike from Lake Rubikiai are characterized by average growth, compared to other populations from various geographical locations. No significant differences were established between the growth of pike in mesotrophic and eutrophic lakes. Pike growth rate did not correlate with lake surface area, maximum or mean depth, and negatively correlated with bogginess in mesotrophic lakes and limpidity and bogginess in eutrophic lakes (P < 0.05). [ABSTRACT FROM AUTHOR]

The effects of maximum, minimum, and slot length limits on the sizes and relative abundance of northern pike Esox lucius were evaluated in 22 Minnesota lakes. The regulations were implemented in 1989-1998 and lasted 9-15 years. As preregulation information was available back to the 1970s, the evaluation periods covered 21-37 years. Comparisons were made with reference populations from 47 ecologically similar lakes during the same extended period. Although the regulations did not achieve management objectives in every lake, the broader-scale, statewide finding was that they improved the size structure of northern pike populations but produced no consistent trends in relative abundance. The improvements were detected against the backdrop of reference populations that initially appeared to have similar sizes and relative abundances. Maximum length limits protecting fish over 20, 22, and 24 in produced significant long-term increases in the percentages of northern pike 24 in and longer and 30 in and longer compared with the reference populations. Lakes with 30-in minimum length limits had increased percentages of northern pike 20 in and longer, but the improvements did not carry over to fish 30 in and longer. A mix of slot length limits produced results that are more difficult to interpret but generally improved size structure. A metaanalysis incorporating all of the length regulations indicated that the changes in northern pike size structure in regulated lakes were very large for an ecological experiment. Length limits protected large northern pike, with the expectation that lower yields were an acceptable trade-off for producing larger fish for recreational fisheries. This study reveals the range and magnitude of responses we can reasonably expect from length limits as well as the substantial value of conserving large fish when the goal is improved population size structure. [ABSTRACT FROM AUTHOR]

Fisheries professionals charged with managing muskellunge Esox masquinongy frequently seek population information that requires the ability to identify cohorts as well as individuals; hence, reliable tagging methods are needed. Our approach was to simultaneously assess multiple marking techniques on different life stages of muskellunge over short and long time scales. We evaluated the short-term detection of visible implant elastomer (VIE) and passive integrated transponder (PIT) tags in muskellunge fingerlings in experimental ponds. We compared survival (relative to that of control fish) and tag retention for two PIT tagging locations (the cheek and dorsal musculature) and one VIE location (the jaw). Overwinter survival did not differ between tagged and untagged fish (84-98%), but overwinter PIT tag retention was lower for the cheek (92%) than the dorsal musculature (100%). We also fin-clipped and VIE-tagged (jaw) 1,651 muskellunge fingerlings from 1997 to 2002 to evaluate long-term tag retention in a broodstock lake. In addition, 125 adult muskellunge were captured and PIT-tagged from 2003 to 2006. Muskellunge were sampled annually with trap nets and electrofishing during spring and fall. Only 2 VIE tags were detected in adults marked as fingerlings. The proportion of PIT-tagged adults recaptured ranged from 52% to 84% during the sampling period. Our results indicate that both VIE and PiT tags are viable short-term marks for muskellunge fingerlings, while PIT tags appear to be reliable long-term tags when implanted in the dorsal musculature of adults. [ABSTRACT FROM AUTHOR]

Background: Salmonids are one of the most intensely studied fish, in part due to their economic and environmental importance, and in part due to a recent whole genome duplication in the common ancestor of salmonids. This duplication greatly impacts species diversification, functional specialization, and adaptation. Extensive new genomic resources have recently become available for Atlantic salmon (Salmo salar), but documentation of allelic versus duplicate reference genes remains a major uncertainty in the complete characterization of its genome and its evolution. Results: From existing expressed sequence tag (EST) resources and three new full-length cDNA libraries, 9,057 reference quality full-length gene insert clones were identified for Atlantic salmon. A further 1,365 reference full-length clones were annotated from 29,221 northern pike (Esox lucius) ESTs. Pairwise dN/dS comparisons within each of 408 sets of duplicated salmon genes using northern pike as a diploid out-group show asymmetric relaxation of selection on salmon duplicates. Conclusions: 9,057 full-length reference genes were characterized in S. salar and can be used to identify alleles and gene family members. Comparisons of duplicated genes show that while purifying selection is the predominant force acting on both duplicates, consistent with retention of functionality in both copies, some relaxation of pressure on gene duplicates can be identified. In addition, there is evidence that evolution has acted asymmetrically on paralogs, allowing one of the pair to diverge at a faster rate. [ABSTRACT FROM AUTHOR]

The form of Darwinian selection has important ecological and management implications. Negative effects of harvesting are often ascribed to size truncation (i.e. strictly directional selection against large individuals) and resultant decrease in trait variability, which depresses capacity to buffer environmental change, hinders evolutionary rebound and ultimately impairs population recovery. However, the exact form of harvest-induced selection is generally unknown and the effects of harvest on trait variability remain unexplored. Here we use unique data from the Windermere (UK) long-term ecological experiment to show in a top predator (pike, Esox lucius) that the fishery does not induce size truncation but disruptive (diversifying) selection, and does not decrease but rather increases variability in pike somatic growth rate and size at age. This result is supported by complementary modelling approaches removing the effects of catch selectivity, selection prior to the catch and environmental variation. Therefore, fishing most likely increased genetic variability for somatic growth in pike and presumably favoured an observed rapid evolutionary rebound after fishery relaxation. Inference about the mechanisms through which harvesting negatively affects population numbers and recovery should systematically be based on a measure of the exact form of selection. From a management perspective, disruptive harvesting necessitates combining a preservation of large individuals with moderate exploitation rates, and thus provides a comprehensive tool for sustainable exploitation of natural resources. [ABSTRACT FROM AUTHOR]

Methods for quantifying selection pressures on adaptive traits affected by size-selective fishing are still scarce, and none have as yet been developed for recreational fishing. We present an ecologically realistic age-structured model specifically tailored to recreational fishing that allows estimating selection differentials on adaptive life-history traits. The model accounts for multiple ecological feedbacks, which result in density-dependent and frequency-dependent selection. We study selection differentials on annual reproductive investment under size-selective exploitation in a highly demanded freshwater recreational fish species, northern pike ( Esox lucius L.). We find that recreational angling mortality exerts positive selection differentials on annual reproductive investment, in agreement with predictions from life-history theory. The strength of selection increases with the intensity of harvesting. We also find that selection on reproductive investment can be reduced by implementing simple harvest regulations such as minimum-size limits. The general, yet computationally simple, methods introduced here allow evaluating and comparing selection pressures on adaptive traits in other fish populations and species, and thus have the potential to become a tool for evolutionary impact assessment of harvesting. [ABSTRACT FROM AUTHOR]

Uranium mining and milling operations in northern Saskatchewan (Canada) release effluents with elevated levels of certain trace metals and metalloids, including selenium. The goal of the present study was to evaluate the presence of seleniuminduced deformities in northern pike (Esox lucius) and white sucker (Catostomus commersoni) larvae originating from adults collected downstream of a uranium mine. Eggs were fertilized in the field and incubated in the laboratory following a two-way (crossover) analysis-of-variance experimental design to discriminate effects from maternal transfer versus those from exposure to site water in the developing embryos. Selenium concentrations in northern pike and white sucker eggs (8.02 and 4.89 μg/g dry wt, respectively; mean ± standard error throughout) from the exposure site were approximately two- to threefold higher than reference (2.35 ± 0.20 and 1.94 ± 0.25 μg/g dry wt, respectively). Among all evaluated deformities (skeletal curvatures, craniofacial deformities, fin deformities, and edema), only edema in white sucker fry from the exposure site was slightly elevated (∼3%) compared to reference. The occurrence of edema, however, can be associated with factors other than selenium (e.g., other metals and organic compounds). Both fish species displayed strong linear relationships between the selenium concentrations in eggs and other tissues (muscle, liver, kidney, and bone), suggesting that selenium concentrations in eggs could be predicted from selenium concentrations in adult tissues. The lack of a clear, toxic response in the present study is in agreement with selenium thresholds for early life-stage deformities reported in other studies, with egg selenium concentrations in northern pike and white sucker collected at the exposure site being less than the 10 μg/g (dry wt) threshold associated with the presence of deformities. [ABSTRACT FROM AUTHOR]

The hypothesis that vagility, or tendency to move, in pike Esox lucius can be predicted from individual home range was tested using telemetry. Independently of fish size, mean annual excursion distance was positively correlated to winter (0·02–0·95 ha) and spring (0·02–0·59 ha) home ranges but not summer and autumn home ranges. [ABSTRACT FROM AUTHOR]

The object of this study was to test site fidelity of female pike Esox lucius and to contrast the activity centre size in summer and winter in a 25 ha lake in north-eastern Germany using radio telemetry. Weekly 24 h tracking and two 96 h tracking exercises were conducted by boat from June to December 2005 and by walking on surface ice from January to February 2006. Positions of 12 E. lucius [total length ( LT) = 450–733 mm] were recorded every 3 h within a 24 h tracking cycle. Site fidelity to individual summer activity centres was tested by translocating eight E. lucius away from their activity centre. All translocated E. lucius returned to their summer activity centre within 6 days, which provided evidence of site fidelity of E. lucius. There was no relation between E. lucius LT or the translocation distance and return time to the activity centre after translocation. In winter, the activity centre size of E. lucius was significantly larger than in summer, but there was considerable overlap between the sites chosen in winter and those in summer. The seasonal variation in activity centre size possibly reflected changes in habitat structure ( e.g. collapse of structured vegetated habitats in winter) or prey fish distribution. [ABSTRACT FROM AUTHOR]

The influence of the invasive black bullhead Ameiurus melas on the predatory efficiency of the pike Esox lucius was investigated using an additive experimental design. Pike predatory success on 0+ years roach Rutilus rutilus was significantly reduced in the presence of black bullhead. Among the different hypotheses that may explain such a pattern, the hypothesis of direct competition between pike and black bullhead was not verified, as black bullhead hardly fed on roach. Similarly, pike predatory efficiency did not decrease with turbidity, rejecting therefore the hypothesis of an indirect effect through black bullhead-generated turbidity. Therefore, the reduced predatory efficiency of pike was probably related to behavioural interference between pike and black bullhead. These laboratory results confirm the potential negative impact of black bullhead on native European fauna, with a particular emphasis on pike, which is a top predator considered as vulnerable in some European regions. [ABSTRACT FROM AUTHOR]

In the northern hemisphere, pike ( Esox lucius Linnaeus) is one of the most important recreational fisheries resources, and regulatory or voluntary catch-and-release angling is common. No information is available about the potential sublethal impacts on pike that catch-and-release fishing may cause, such as behavioural alterations and changes in habitat choice after release. Radio telemetry with N = 20 pike was used to test the hypothesis that fish modify behaviour by reducing movement as a reaction to a catch-and-release event in a previously unfished, slightly eutrophic lake, having an area of 25 ha and located in northeastern Germany. During a 7-month tracking period, activity of pike was monitored for consecutive 24 h every week. Minimum displacement per hour (m) and distance to shore (m) were significantly lower upon the first post release tracking compared to tracking before the capture. Two tracking events after capture, both movement and distance to shore were similar to those measured during pre-angling. There were no significant relations between the change in movement and distance to shore and size of pike. In terms of habitat choice, pike significantly selected for reed and avoided the pelagic area over the whole study period that was not influenced by catch-and-release angling. The results indicated that catch-and-release induces short-term behavioural alterations in pike, probably explained by physiological disturbances and facilitated by evolved anti-predation behaviours. Such alterations, however, seem to be of short duration and reversible suggesting sublethal catch-and-release impacts on pike behaviour are limited. [ABSTRACT FROM AUTHOR]

The pike, Esox lucius Linnaeus, is a predatory fish that supports important fisheries and could substantially impact prey populations around the temperate northern hemisphere. Consumption of prey by pike is most readily estimated using the energy budget to calculate food intake indirectly using estimates of growth rate and metabolism. Resting metabolic rate, R s, is a particularly important component of such calculations. Here, the available estimates of R s are reviewed and compared. Scaling coefficients for variation with body mass are consistent between the two studies in which they have been derived (0.81, 0.82). However, the effect of temperature on R s markedly varies among studies ( Q 10 from 1.73 to 4.80). There is substantial variation in R s (twofold to fourfold) among studies when temperature and fish size are accounted for. This variation is shown to have a large effect on energy budget calculations of energy intake and to be sufficient to account for imbalances in published budgets. These effects depend on age of pike and season; in one energy budget model, a 50% reduction in R s resulted in decrease of 19–42% in estimated energy intake of pike. Potential causes of among-study variation in R s are discussed and it is recommended that standard techniques by applied in the future to differentiate between genuine biological variation among populations and experimental factors. [ABSTRACT FROM AUTHOR]

Northern pike (pike) Esox lucius Linnaeus are broadly distributed across Wisconsin and provide an important sport fishery for anglers. Historical management has included use of angling regulations, stocking, and protection of critical habitat areas. Pike management is often a lower priority in comparison to more intensively managed species such as muskellunge Esox masquinongy Mitchell and walleye Sander vitreous. Pike provide angling opportunities year around, with higher catch rates and live release during open water, and higher harvest rates during winter. While length of pike caught during the two seasons is generally similar, there is some evidence that larger fish are caught during winter months. Results from minimum length limit changes implemented in 1995 have been equivocal and warrant further monitoring using standardized protocol to better determine effects on populations. If natural recruitment is not limited, pike populations can reach high densities and stunting can result. Loss of nearshore habitat has continued at an increased rate as more lake homes are built and shorelines graded, and altered with riprap, sand blankets, or sea walls. If natural recruitment is lacking, fry or fingerling stocking sustains or rehabilitates populations. Most pike stocking occurs in the southeastern portion of the state where habitat loss has been extensive. Stocking in other areas is largely to re-establish populations following a chemical reclamation or from winterkill. Future management needs to establish sampling protocols to ensure comparable data on both a temporal and a spatial scale. Long-term monitoring with these methods is essential to help determine effects of various factors (e.g., regulations, habitat loss) on populations. [ABSTRACT FROM AUTHOR]