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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We used multiplex PCR of 20 pooled individuals from each of 12 populations to screen a total of 80 published and unpublished microsatellite loci in the Northern pike Esox lucius, a species known to exhibit low genetic variability, thus predisposing it as a model species to test our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]

Top-level piscivores are highly sought after for consumption in freshwater fisheries, yet these species contain the highest levels of the neurotoxin monomethylmercury (MMHg) and therefore present the greatest concern for MMHg exposure to humans. The slow elimination of MMHg is one factor that contributes to high levels of this contaminant in fish; however, little quantitative information exists on elimination rates by top predators in nature. We determined rates of MMHg elimination in northern pike (Esox lucius) by transferring fish that had naturally accumulated isotope-enriched MMHg (spike MMHg) through a whole-lake Hg loading study to a different lake. Over a period of ~7 y, pike were periodically recaptured and a small amount of muscle tissue was extracted using a nonlethal biopsy. Spike total mercury (THg) persisted in muscle tissue throughout the entire study despite discontinuing exposure upon transfer to the new lake. Spike THg burdens increased for the first ~460 d, followed by a decline to 65% of original burden levels over the next 200 d, and subsequently reached a plateau near original burden levels for the remainder of the study. We estimated the half-life of muscle THg to be 3.3 y (1193 d), roughly 1.2- to 2.7-fold slower than predicted by current elimination models. We advocate for further long-term field studies that examine kinetics of MMHg in fish to better inform predictive models estimating the recovery of MMHg-contaminated fisheries. [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]

Abstract: The strontium (Sr) or Sr:Ca ratio in otoliths has been widely used in the last decade to describe the migration histories of fish between fresh and marine waters. However, reference experimental studies of particular species and waters are necessary to confirm the underlying assumptions and evaluate the applicability of this tool to field data. Laboratory experiments indicated that juvenile, anadromous pike (Esox lucius L.) from the Baltic Sea reared in successively increasing salinities (from 0 to 7‰) for 110d accumulated Sr in their otoliths according to a positive relationship with waterborne Sr. When the pike were given prey fish from brackish (7‰) environments, the otolith Sr:Ca ratio increased more than in fish given prey from freshwater lakes. Pike held at constant salinity (7‰) and given prey fish from the same salinity environment had an Sr:Ca ratio of 6.9×10−3. The ratio decreased successively for fish given prey from freshwater (4.4×10−3) or kept in freshwater and given food from brackish water (3.1×10−3). Fish exposed to freshwater and given prey fish from freshwater displayed no increase in Sr:Ca ratio (1.6×10−3). The experiments demonstrated that the Sr:Ca ratio may be used to describe the migration history of pike between rivers and the Baltic Sea. The maximum Sr:Ca value for pike given marine-origin food corresponded to those of fish collected from the Baltic Sea. [Copyright &y& Elsevier]

We developed decision trees (J48 algorithm) to predict the distribution of the pike (Esox lucius). Based on a historical data, 75 sampling sites were considered for the pike in 7 stream basins in Flanders (Belgium). In total, 108 instances were available in the given sites. The measured variables consisted of a combination of the structural-habitat, physical–chemical and biological variables (biomass, abundance and presence/absence of the pike). The predictive power of decision trees was assessed on the basis of the number of Correctly Classified Instances (CCI %) and Kappa statistic (k). In order to reduce the noise in the data and improve the predictive results with regard to complexity and accuracy of the predictions, different Pruning Confidence Factors (PCFs) were tested. The obtained results showed that the prediction of the pike (based on presence/absence data) was acceptable in terms of two model evaluations (CCI>70% and k >0.40). The habitat variables had more contribution to the prediction of distribution of pike relative to the water quality ones. The developed model presented a logical relationship between distribution of the pike and distance from the source, slope and followed by depth. These models can as such become essential tools to encourage river managers to make the necessary investments and/or activity changes as desired by society. [Copyright &y& Elsevier]

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]

Background and purpose: Aquatic ecosystems pollution with heavy metals, have always been a major concern for aquatic organisms and human health. Contaminants such as heavy metals get accumulated along the food chain and then transmitted to human body. Levels of contaminants in fish are of particular interest because of the potential risk to humans consuming them. This paper examines the levels of cadmium, lead, zinc and copper in muscle tissue of Esox lucius from the Anzali international wetland and compared them whit human health standards. Materials and methods: In this study 26 Pike perch (Esox lucius) were collected from the wetland by multimesh gill nets in September 2010. After sampeles digestion with concentrated nitric acid, they were analyzed for Pb in a graphite furnace atomic absorption spectrophotometer and for Cd, Cu, and Zn in a flame atomic absorption spectrophotometer. Results: Mean concentration of Cd, Pb, Cu and Zn were 0.82 ± 0.06, 0.22 ± 0.02, 5.68 ± 0.31, 54.26 ± 0.87 (µg/g dry weight) respectively. Data analysis showed that no significant correlation exist between Pb, Cu and Zn concentrations with body weight and length but a significant negative correlation observed between Cd concentration with body weight and body length. Conclusion: The levels of Zn, Cu and Pb was below than the established limits by WHO, FAO, and EPA but levels of Cd was exceeded than the limits of WHO and EPA standards. These results can be a warning for consumers of these fish, especially vulnerable people. Daily intake calculation showed that a meal consumption of this fish per week no prohibition for an adult consumer. [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]

Abstract: Northern pike (Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17μm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6μm, respectively. The osmolality of seminal plasma ranged from 228 to 350mOsmolkg−1 (average: 283.88±33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media (P <0.05). In general, the greatest percentage of motile spermatozoa and highest spermatozoa velocity were observed between 125 and 235mOsmolkg−1. Osmolality above 375mOsmolkg−1 inhibited the motility of spermatozoa. After triggering of sperm motility in activation media, beating waves propagated along the full length of flagella, while waves appeared dampened during later periods in the motility phase, and were absent at the end of the motility phase. By increasing osmolality, the velocity of spermatozoa reached the highest value while wave length, amplitude, number of waves and curvatures also were at their highest values. This study showed that sperm morphology can be used for fish classification. Sperm morphology, in particular, the flagellar part showed several changes during activation in distilled water. Sperm motility of pike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters. [Copyright &y& Elsevier]

Abstract: We examined the physiological and behavioural consequences of, and recovery from, catch-and-release related stressors using a combined laboratory and field study in northern pike (Esox lucius L.). A laboratory experiment was conducted to investigate the recovery dynamics of physiological indicators of stress resulting from a simulated angling event resulting in exhaustion, with and without additional air exposure of 300s. In addition, a field study using a combination of physiological and behavioural assessment was conducted to assess the long-term consequences of exhaustive exercise and various air exposure durations. Exhaustive exercise for 60s led to increased muscle lactate, decreased tissue energy stores, and alterations in plasma ionic status. Recovery from physiological disturbance was rapid with all physiological variables except plasma glucose returning to baseline levels after 6h. The recovery profile was largely unaffected by air exposure of 300s that simulated extended de-hooking time. The field component of our study verified the impact of exhaustive exercise on blood lactate values, but did not detect any impact of air exposure varying between 0s and 300s on physiological stress indicators. However, pike exposed to air for 300s were behaviourally impaired in the first hour post-release indicating that despite limited effects on physiological status air exposure resulted in significant impairment of organismal performance. Behavioural patterns returned to normal within several hours. In a three-week post-release monitoring period no mortality occurred. Our results emphasize that angling-induced stressors result in physiological and behavioural disturbances, but that recovery is quick. This suggests that pike are relatively resilient to catch-and-release related stressors but air exposure durations should be kept <300s to minimize behavioural impairment. [Copyright &y& Elsevier]

Abstract: Genetic analyses allowed management and conservative programmes specifically designed for biodiversity conservation purposes. To date, no information is available for the N e definition of any Italian northern pike population, because of their wide, highly fragmented, distribution. Low gene flow levels may have caused some of the health population problems emerging from professional fisheries data, underlining a marked reduction of these populations. This paper reports the first estimate of genetic N e of the Lake Trasimeno''s northern pike, by means of microsatellites data, over the last four decades compared with five other significant Italian populations. N e values were evaluated through specific software and θ estimator. The N e results confirm that, despite a marked reduction between 1966 and 1997 and a less than optimal status, the Trasimeno population shows a positive trend in its health status, presumably due to proper management programmes. Considerations on the biological conservation and management of this pike population are also reported. [Copyright &y& Elsevier]

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 article focuses on the published taxonomic accounts of Neoechinorhynchus tenellus from Esox lucius Linnaeus and Sander vitreus. Its original type material was studied and found that their present state are little use for clarifying characters. The revised description includes trunk of males and females that is widest in anterior, the lateral anterior hooks which are marked larger, and the middle and posterior hooks with discoidal bases.

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]

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]

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]

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]

The objective of this study was to contrast movement rates and habitat choice of pike ( Esox lucius Linnaeus) in mid-summer and mid-winter in a 25-ha lake (Kleiner Döllnsee, northeastern Germany) using radio-telemetry. Positional telemetry for consecutive 96-h was conducted by boat in July 2005 and by walking on surface ice in January/February 2006. Positions of pike ( N = 11) were recorded with a GPS unit corrected by a reference station. Movement rates, distance to shore and habitat use were compared between summer and winter and relative to daytime and fish length. Pike moved significantly more in summer, and during summer had activity peaks in twilight periods. In winter, pronounced activity peaks at specific daytime periods were missing and pike chose habitats significantly closer to shore. In summer, submerged macrophyte beds were positively and pelagic areas negatively selected. In winter, pike negatively selected shallow open water in the littoral zone, and there was a tendency to avoid the pelagic. Movement rate and distance to shore were significantly and positively related to the size of pike. [ABSTRACT FROM AUTHOR]

The effect of pike Esox lucius predation on the mortality of newly stocked Atlantic salmon Salmo salar smolts was investigated in the Pyhäjoki River, Finland. The number of smolts eaten by pike was assessed by estimating the size of the pike population (mark–recapture experiment) and studying the stomach contents of pike. Before recapturing the pike, approximately 39,700 smolts were stocked upstream of the 2.5-km-long (89-ha) research area. The estimated size of the >40-cm pike population was 1507 (95% CL 1012–4731) individuals (17 pike and 29.8 kg·ha−1). Pike were estimated to eat 29% of the released smolts during 1 week. The diet of the pike in the research area consisted almost entirely of smolts, whereas in the reference area with no stocked smolts, the meal sizes were significantly smaller and the importance of smolts as prey was substantially lower. Pike <40 cm had not eaten any smolts, probably indicating a size refuge for the smolts, or alternatively fear of intraspecific interactions or cannibalism of pike. [ABSTRACT FROM AUTHOR]

1. The keystone piscivore northern pike Esox lucius can structure fish communities, and models predicting pike-focused connectivity will be important for management of many waters. 2. We explored the ability of pike to colonize upstream locations and modelled presence–absence in lakes based on landscape features derived from maps. An upstream connectivity model (UC model) was generated using data from 87 lakes. We validated the UC model with retrospective whole-lake experiments involving introductions ( n = 49) and extirpations (by rotenone) of pike ( n = 96), as well as with the natural distribution of pike in lakes ( n = 1365) within 26 drainage basin networks in northern Sweden. 3. The UC model predicted the incidence of pike in lakes with stream-connections with 95·4% accuracy, based mainly on a single variable, SV5max, that measures the minimum distance found between 5 m elevation intervals (= maximum stream slope) along watercourses from nearest downstream source of potential immigrants. Recolonizations of pike in rotenone lakes generated a near-identical classification tree, as in the UC model. The classification accuracy of pike presence in the external validation procedure ranged from 88·7 to 98·7% between different drainage basins. Predictions of pike absence were not as accurate, due possibly to undetected introductions, but still lead to 86·6% overall accuracy of the external validation. Most lakes lacking pike, but misclassified as having pike based on low SV5max, were isolated from downstream sources of pike by subsurface streamflow through bouldery areas (SSB). 4. Synthesis and applications. The variable SV5max provide managers with a tool for revealing the location and severity of natural dispersal barriers to pike (and logically also barriers to other species with equivalent or less dispersal capacity). Because presented models only require map-based information, and have high predictive power, they may have the potential to be of fundamental use in predicting distribution of freshwater fish. These predictions may provide the means for prioritizing in risk assessment and control programmes to combat pike invasions, as well as contribute to determining a reference state of species incidence in specific lakes. Our results also point towards a possibility that, even where stream slope is low, long-term effective barriers may be designed that mimic natural SSB. [ABSTRACT FROM AUTHOR]

Quantifying the effects of density-dependent and density-independent factors in demographic and dispersal processes remains a major challenge in population ecology. Based on unique long-term capture-mark-recapture (CMR) data (1949-2000) on pike (Esox lucius) from Windermere, United Kingdom, we provide estimates of density-dependent and density- independent effects, under the influence of individual size and sex, on natural survival, fishing mortality, and dispersal. Because survival is expected to be related to the individual growth process, we also explore the degree of parallelism between the two processes by applying the best-supported survival model structure to individual growth data. The CMR data were analyzed using sex- and age-structured multistate models (two lake basins: north and south) assuming no seasonal variation in survival and dispersal. Total survival and dispersal probabilities were insensitive to this assumption, and capture probability was shown to be robust to assumptions about intra-annual variation in survival and dispersal. The analyses revealed that large pike (>55 cm) displayed marked basin-specific differences in survival and dispersal responses to the abundance of conspecifics in which pike from the south basin show high density dependence in survival and a low degree of density dependence in dispersal, whereas the opposite was found for those of the north basin. Both large- and small-pike dispersals were found to be dependent upon the between-basin gradient in perch (Percafluviatilis, the main prey) abundance, but most so for north-to-south dispersal. The strength and pattern of density-dependent mortality in small pike was influenced by temperature in a peculiar way: at low summer temperatures survival was lowest at high small-pike abundances and low perch abundances; at low temperatures, survival was lowest at high small-pike abundances and high perch abundances. Analyses of individual small-pike growth trajectories showed a similar modulation of the positive perch abundance effect on growth rate when temperature increases. The growth analysis also indicated that cannibalism may be biased in favor of rapidly growing individuals or at least increased growth rate for the surviving individuals. Altogether, this study provides evidence of a complex interplay between density- dependent and density-independent factors affecting survival, dispersal, and individual growth of an aquatic top predator. [ABSTRACT FROM AUTHOR]

The short-term tolerances of northern pike, Esox lucius L., fry reared in a freshwater hatchery, to salinity were examined in the laboratory. Survival of two size groups of pike fry (mean length 21 ± 2 mm SD and 37 ± 4 mm SD) was examined over 72- to 96-h periods at 9–14 ppt salinity in combination with temperatures of 10, 14 and 18 °C. A parametric survival model found a significant correlation between survival of pike fry and temperature and salinity, respectively. LC50 values after 72 h were between 11.2 and 12.2 ppt, being lowest at 10 °C. Pike fry did not survive more than 13 ppt. Mortality at 12 ppt was significantly faster at 18 °C than 10 or 14 °C. Moreover, mortality was higher and faster for large than for small pike fry at 12 ppt and 14 °C. These results imply that pike raised in fresh water can survive stocking into brackish waters below 11 ppt at least for a short time. [ABSTRACT FROM AUTHOR]

1. Stocking of piscivores in shallow, eutrophicated lakes to reduce cyprinid densities is a common approach in lake restorations. Young-of-the-year (YOY) pike Esox lucius are frequently used to reduce cyprinid densities, but their effectiveness is equivocal. This study uses a simple model to assess the efficacy of pike stocking as a lake restoration tool. 2. The model evaluates YOY pike consumption in relation to different survival and growth patterns, timing of stocking, degree of piscivory of pike as well as YOY cyprinid growth patterns and productivity. The parameters used in the model are obtained from field surveys in eight study lakes stocked with YOY pike as well as from the literature. 3. Our model showed that all parameters studied were important for predicting the effects of pike stocking on cyprinids. In particular, body size at stocking, cyprinid production and pike survival were good predictors of biomanipulation success. 4. However, our model showed that only under very specific circumstances will stocking of YOY pike result in a reduction of YOY cyprinid densities large enough to affect water quality. 5. The findings of this study question the efficacy of pike stocking as an appropriate and reliable tool for restoration programmes in shallow lakes, and indicate that when used efforts should be made to optimize the timing of stocking in relation to YOY cyprinid production and to increase the stocking body size of the pike. [ABSTRACT FROM AUTHOR]