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Esox lucius Linnaeus, 1758 [N]—Northern pike Taxonomy. Original description: Esox lucius Linnaeus,1758:314 [Europe; possible syntypes:BMNH1853.11.12.114 (1, skin)]. Type catalog: Wheeler 1958:209].— Afghanistan synonyms: None.—Revisions: Berg (1948: 458).— Illustration: Berg (1948: 459, fig. 274). Status in Afghanistan. First record from Afghanistan by Berg (1948: 463); confirmed by Coad (1981: 8).— Afghanistan materials: None. Distribution and habitat. Distribution in Afghanistan: Pitnyak (Amu Darya River system, into Aral Sea).—General distribution:Circumpolar in Northern Hemisphere:North America, Europe, and northern Asia; widely introduced elsewhere.—Habitat: This species usually occurs in clear small lakes, shallow vegetated areas of larger lakes, marshes, creeks, and small to large rivers. It moves to deeper, cooler water in the summer. Spawning occurs in shallow flooded marshes associated with lakes, inlet streams to those lakes, or rivers; spawning habitat is basically a flooded area with emergent vegetation. Freshwater, brackish. Economic importance. Commercially important. Conservation. Conservation status in Afghanistan: Unknown.—IUCN: LC (NatureServe 2018).—Threats: No major threats are known.—Moderate sensitivity to human activities.—Keystone species.—Decline status: Stable.—Low priority for conservation action., Published as part of Çiçek, Erdoğan, Fricke, Ronald, Eagderi, Soheil, Sungur, Sevil, Coad, Brian W & Hamdard, Mohammad Hamid, 2023, Fishes of Afghanistan; a revised and updated annotated checklist, pp. 1-69 in Zootaxa 5305 (1) on page 42, DOI: 10.11646/zootaxa.5305.1.1, http://zenodo.org/record/8048564, {"references":["Linnaeus, C. (1758) Systema Naturae. Vol. 1. Ed. X. [Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata]. Impensis Direct. Laurentii Salvii, Holmiae, ii + 824 pp.","Berg, L. S. (1948) s. n. In: Ryby presnych vod SSSR i sopredelnych stan. [Freshwater fishes of the U. S. S. R. and adjacent countries]. Vol. 1. 4 th Edition. Opredeliteli po faune SSSR. [Guide to the fauna of the U. S. S. R.], Moskva. Freshwater fishes of the U. S. S. R. and adjacent countries No. 27. Russian Academy of Sciences, USSR, Moskva, 466 pp. [in Russian. English translation available, Israel Prog. Sci. Transl., Jerusalem, 1962, 504 pp.]","Coad, B. W. (1981) Fishes of Afghanistan, an annoted checklist. National Museum of Canada Publications in Zoology, 14, i - v + 1 - 26."]}

The aim of this research is to compare the average individual weight of the four most important fish species in fisheries (Cyprinus carpio, Silurus glanis, Esox lucius and Sander lucioperca), caught by angling in different parts of the Sava River catchment in Croatia. Significant differences were expressed between the counties along the Sava River catchment, with the smallest specimens (p˂0.05) caught in Vukovar-Sirmium county. Artisanal fishery is mostly developed in that part of the Sava River, along with angling in both countries – Croatia and Bosnia and Herzegovina. Furthermore, the inflow of the River Bosna passes through urban and industrial cities of Bosnia and Herzegovina. It can be concluded that implementing recreational fishing surveys with the specific aim of obtaining data on average individual weight is useful for fishery management.

Northern pike (Esox lucius) was widely distributed in the high latitudes of the northern hemisphere. In China, northern pike was originally distributed only in the upper reaches of the Irtysh River in Xinjiang and has appeared in many water bodies outside the Irtysh River Basin in Northern Xinjiang. A total of four populations were collected from north to south in Xinjiang, including Irtysh River (RIR), Ulungu Lake (LUL), a small lake nearby Ulungu River (LJD), and Bosten Lake (LBO). We estimated population genomic parameters, performed gene flow analysis, and estimated the effective population size of each population. The proportion of individuals with high inbreeding coefficient (F ≥ 0.0625) accounted for 36.4% (44/121) of all sequenced individuals, approximately 4.5% (1/22) in LUL, 25.9% (7/27) in LBO, 42.9% (18/42) in RIR, and 60% (18/30) in LJD. RIR had the highest mean of genomic relatedness (coancestry coefficient = 0.025 ± 0.040, IBD = 0.036 ± 0.078). Gene flow results showed that the population spreading was from RIR into two branches, one was LBO, and the other continued to split into LUL and LJD, and migration signal from LBO to LUL was detected. Our results suggested that the extinction risk of northern pike was very low in Xinjiang of China, and the controlled capture fishery of northern pike could be developed reasonably.

Considerable genetic divergence emerged among the barcoded E. lucius from the northern lakes, between the fish of the western lakes of the sampled region (Chalain, Annecy) compared to other northern lakes. Despite evidence suggesting the additional presence of E. cisalpinus in Lake Geneva in the first half of the 19 th century (barcoding of historic samples from a museum collection) [154], all ten Esox barcoded from Lake Geneva in Projet Lac were genetically E. lucius. Two lineages were apparent among the Geneva pike however, with five of the fish sharing the lineage of a historically sampled E. lucius (also collected in the first half of the 19 th century) [154] 4. This lineage was also shared with two pike from Lake Joux.The five other E. lucius from Lake Geneva shared a lineage with fish of other northern perialpine lakes (including also one fish from Lake Joux). Another distinct lineage of E. lucius contained all barcoded pike from Chalain (3 fish) and one from Annecy. This lineage clustered with GenBank reference samples mostly from Canada (as well as other parts of Europe) and may reflect the translocation of fish for stocking., Published as part of Alexander, Timothy & Seehausen, Ole, 2021, Diversity, distribution and community composition of fish in perialpine lakes – " Projet Lac " synthesis report, Eawag: Swiss Federal Institute of Aquatic Science and Technology on page 132, DOI: 10.5281/zenodo.5779569

Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.

WOS: 000470363000001, Ladik Lake (Samsun, Turkey) is a natural landscape under the threat of pollution because of urban, agricultural and industrial activities. In this study, accumulation of heavy metals (Al, Ba, Cr, Cu, Fe, Mn, Pb and Zn) in the tissues (muscle, liver and gill) of sediment dwelling pike fish and in different substrates of Ladik Lake were investigated. Seasonal haematological, biochemical and histopathological parameters of the carp are also reported. In general, heavy-metal levels in water and sediment samples were found in the highest level in summer and the lowest in autumn. Histopathologic changes in the tissues of the fish (liver and gill) were at the minimum in winter while it was highest in summer. Blood biochemical parameters exhibited higher level in summer in comparison with other seasons. Al, Ba, Cr, Mn and Zn levels in the tissues of the fish were in the order gill>liver>muscle in all seasons. The levels of Cu, Fe and Pb were in the sequence liver>gill>muscle. Cr, Cu, Pb and Zn levels were determined to be in high level in the tissues of the fish with respect to the literature values. The heavy-metal levels in Ladik Lake and the fish health need to be regularly monitored for a sustainable environmental health.

In the stomach of a pike from the Danube Delta we have found seven Perccottus glenii individuals. Their message indicated that in the Danube Delta P. glenii has already large population. Also, it proves that in its habitats, the pike can consume numerous individuals of this invasive species. Their gut contents prove that P. glenii hunted near the shores, ingesting numerous terrestrial preys.

Background. Temporal variability in fish reproductive features is influenced by environmental and spatial variations. Given the wide distribution of northern pike, Esox lucius Linnaeus, 1758, in the northern hemisphere, important reproductive features such as the initiation of the spawning activity are likely to vary with latitudinal gradients. The overall goal of the presently reported study was to answer basic questions regarding the reproductive biology of the pike and to discuss changes in the timing of the onset of spawning activity in relation to geographical locations and the water temperature in the Anzali Wetland compared to higher latitudes. Materials and methods. Monthly samples (537 specimens in total) were collected from the Anzali Wetland (southwest of the Caspian Sea) from July 2012 through July 2013. Samples were macro- and microscopically examined, and their maturity stages were identified, so that spawning season, monthly distribution of maturity stages, oocytes development, spawning strategy, length at 50% maturity, and fecundity were estimated. Results. The gonadosomatic index, oocyte size-frequency distribution, and histological examination suggested a relatively short spawning season, from February through March. The short annual spawning period and the oocyte size-frequency distribution demonstrated that pike is a total spawner with group synchronous oocyte development. The length at 50% maturity was 28.5 and 33.9 cm FL for males and females, respectively. Absolute fecundity values ranged from 4423 to 48471 oocytes, with mean (± standard error) of 16481 ± 2705 oocytes and the relative fecundity was estimated as 26.9 ± 1.6 oocytes per gram of mature female. Conclusion. The most important findings of this study are: the earlier initiation and relatively shorter duration of the reproductive activities of pike in the south Caspian region compared to northern geographical regions. The results emphasize the need for specific management strategies based on seasonal measures for pike such as: fish size limits, limitation of catches during the spawning season, limitation of the boat number, and closure of the spawning area during spawning months.

5 pages; International audience; Pumpkinseed (Lepomis gibbosus) originates from North America and has been widely introduced in Europe where invasive populations have established. We tested the effectiveness of a biomanipulation approach based on the stocking of a native top-predatory species, the northern pike (Esox lucius), in 23 small and oligotrophic ponds at the Pinail Nature Reserve (Vienne, France) among which 10 ponds were stocked twice. In addition, 16 ponds with similar environmental characteristics were used as control with no pike stocking. Our study revealed that, even with limited space and limited alternative prey species, northern pike did not eradicate pumpkinseed populations. Instead, we found that pumpkinseed were younger and larger when reaching sexual maturity in the stocked ponds, suggesting an increased growth rate in ponds with the predator. These results suggest that invasion populations might adapt and respond to management practices. These changes were likely driven by an adaptation to predation pressure and/or changes in food availability with reduced intraspecific competition. Importantly, such changes might actually modify the level of invasiveness potential of non-native populations and lead to counterproductive results for managers.

The chief aim of invasive species management is to prevent biological invasions by taking measures for suppressing or eradicating potential invaders. Biological control as a management tool is frequently implemented to reduce the population size, adverse ecological impacts, and dispersal of invasive species. The efficacy of biological control measures in managing thePerccottus gleniipopulation was assessed in four small lakes of Lithuania. The biocontrol was carried out by introducing the native piscivorous fishesEsox luciusandPerca fluviatilisinto the invaded water bodies for two successive reproductive seasons. The stocking of these fishes led to an instant reduction inP. gleniiabundances, and the outcome of the repeated stocking was complete disappearance of the species from the water bodies investigated. Our study proves that native predator fishes can be successfully used for eradicating well-establishedP. gleniipopulations in small eutrophic lakes. We hope the current study results will contribute to developing risk-commensurate methodologies for the control of invasiveP. gleniipopulations in small water bodies.

The increasing popularity of pike in angling and fish farming has created a need to increase pike production. However, intensive pike farming is subject to limitations due to diseases and pathogens. Sodium chloride (NaCl) could be a good alternative to chemotherapeutics, especially for protecting the fish against pathogens and parasites at early life stages. However, the impact of high salinity on the symbiotic bacteria inhabiting freshwater fish is still unclear. Therefore, our objective was to analyze the gut microbiome to find possible changes caused by salinity. In this study, the influence of 3&permil, and 7&permil, salinity on pike fry was investigated. High-throughput 16S rRNA gene amplicon sequencing was used to profile the gut microbiome of the fish. It was found that salinity had a statistically significant influence on pike fry mortality. Mortality was highest in the 7&permil, salinity group and lowest in the 3&permil, group. Microbiological analysis indicated that Proteobacteria and Actinobacteria predominated in the pike gut microbiome in all examined groups, followed by lower percentages of Bacteroidetes and Firmicutes. There were no statistically significant differences in the percent abundance of bacterial taxa between the control group and groups with a higher salinity. Our results suggest that salinity influences the gut microbiome structure in pike fry, and that 3&permil, salinity may be a good solution for culturing pike at this stage in their development.

Background The Northern pike, Esox lucius, is a large, long-lived, top-predator fish species and occupies a broad range of aquatic environments. This species is on its way to becoming an important model organism and has the potential to contribute new knowledge and a better understanding of ecology and evolutionary biology. Very few studies have been done on the intestinal pathology of pike infected with helminths. The present study details the first Italian record of adult Acanthocephalus lucii reported in the intestine of E. lucius. Results A total of 22 pike from Lake Piediluco (Central Italy) were examined, of which 16 (72.7%) were infected with A. lucii. The most affected areas of gastrointestinal tract were the medium and distal intestine. The intensity of infection ranged from 1 to 18 parasites per host. Acanthocephalus lucii penetrated mucosal and submucosal layers which had a high number of mast cells (MCs) with an intense degranulation. The cellular elements involved in the immune response within the intestine of pike were assessed by ultrastructural techniques and immunohistochemistry using antibodies against met-enkephalin, immunoglobulin E (IgE)-like receptor (FCεRIγ), histamine, interleukin-6, interleukin-1β, substance P, lysozyme, serotonin, inducible-nitric oxide synthase (i-NOS), tumor necrosis factor-α (TNF-α) and the antimicrobial peptide piscidin 3 (P3). In intestines of the pike, several MCs were immunopositive to 9 out of the 11 aforementioned antibodies and infected fish had a higher number of positive MCs when compared to uninfected fish. Conclusions Pike intestinal tissue response to A. lucii was documented. Numerous MCs were seen throughout the mucosa and submucosal layers. In infected and uninfected intestines of pike, MCs were the dominant immune cell type encountered; they are the most common granulocyte type involved in several fish-helminth systems. Immunopositivity of MCs to 9 out of 11 antibodies is of great interest and these cells could play an important key role in the host response to an enteric helminth. This is the first report of A. lucii in an Italian population of E. lucius and the first account on positivity of MCs to piscidin 3 and histamine in a non-perciform fish.

Baltic Sea populations of the northern pike (Esox lucius) have declined since the 1990s, and they face additional challenges due to ongoing climate change. Pike in the Baltic Sea spawn either in coastal bays or in freshwater streams and wetlands. Pike recruited in freshwater have been found to make up about 50 % of coastal pike stocks and to show natal homing, thus limiting gene flow among closely located spawning sites. Due to natal homing, sub-populations appear to be locally adapted to their freshwater recruitment environments. Management actions should therefore not involve mixing of individuals originating from different sub-populations. We offer two suggestions complying with this advice: (i) productivity of extant freshwater spawning populations can be boosted by modifying wetlands such that they promote spawning and recruitment; and (ii) new sub-populations that spawn in brackish water can potentially be created by transferring fry and imprinting them on seemingly suitable spawning environments.

International audience; Size, caloric value and chemical composition were measured separately in the progeny of two northern pike (Esox lucius) females at 3-day intervals during the endogenous feeding period from hatching to final yolk resorption. Tissue, yolk and entire larvae were analysed separately in three groups of larvae that hatched at different times (between 88 and 106 degree-days post-fertilization). An integrated approach with the Gompertz model was used to compute the yolk conversion efficiency and time to maximum tissue size in early, mid and late hatched larvae. At hatching, unresorbed yolk of early hatched larvae contained more energy (39.20 J) and more protein (0.99 mg) compared to the yolk of larvae that hatched later (38.13 J and 0.92 mg protein for late hatched larvae, p < 0.05). In contrast, a significant reduction in tissue weight (-0.7 mg DW) and protein content (-0.5 mg) was found in early hatched larvae compared to those which hatched later (p < 0.05). Between days 9 and 12 post-hatching (108 and 144 degree-days post-hatching), close to the final yolk resorption, late hatched larvae stopped growing and their tissue began to be resorbed. This tissue resorption time was delayed in early hatched larvae which presented at the end of the experiment a greater tissue weight than late hatched ones. Yolk conversion efficiency in term of energy from hatching to complete yolk resorption stage was significantly higher for early and mid hatched larvae (51 %) compared to late hatched ones (44 %) (p = 0.004). Furthermore, the time to maximum tissue size was found to be negatively related to hatching time which implies that early hatched larvae take longer time to switch from one developmental stage to the next. The maximum tissue dry weight and energy content were found to be reached at approximately the same age post-fertilization for both early hatched and late hatched larvae, suggesting that the principal steps in a fish's lifespan are better correlated with time of fertilization than hatching time.

The biogeography of freshwater fish species during and after late-Pleistocene glaciations relate to how these species are genetically organized today, and the management of these often disjunct populations. Debate exists concerning the biogeography and routes of dispersal for Northern pike (Esox lucius) after the last glaciation. A hypothesis to account for the relatively low modern genetic diversity for E. lucius is post-glacial radiation from refugia, including lakes from within the un-glaciated portions of eastern Beringia. We report the remains of a Northern pike (E. cf. lucius) skull, including bones, teeth, bone collagen and ancient DNA. The remains were preserved at a depth of between 440 and 446 cm in a 670 cm long core of sediment from Quartz Lake, which initiated at ∼11,200 cal yr BP in interior Alaska. A calibrated accelerator mass spectrometer (AMS) radiocarbon age of the collagen extracted from the preserved bones indicated that the organism was dated to 8820 cal yr BP and is bracketed by AMS values from analyses of terrestrial plant macrofossils, avoiding any potential aquatic reservoir effect that could have influenced the radiocarbon age of the bones. Scanning electron microscope images of the specimen show the hinged tooth anatomy typically of E. lucius. Molar C:N (3.5, 1σ = 0.1) value of the collagen from the specimen indicated well-preserved collagen and its mean stable nitrogen isotope value is consistent with the known predatory feeding ecology of E. lucius. Ancient DNA in the bones showed that the specimen was identical to modern E. lucius. Our record of E. lucius from interior Alaska is consistent with a biogeographic scenario involving rapid dispersal of this species from glacial refugia in the northern hemisphere after the last glaciation.

A growing number of studies have been investigating the influence of contemporary environmental factors on population genetic structure, but few have addressed the issue of spatial patterns in the variable intensity of factors influencing the extent of population structure, and particularly so in aquatic ecosystems. In this study, we document the landscape genetics of northern pike (Esox lucius), based on the analysis of nearly 3000 individuals from 40 sampling sites using 22 microsatellites along the Lake Ontario - St. Lawrence River system (750 km) that locally presents diverse degrees of interannual water level variation. Genetic structure was globally very weak (F ST = 0.0208) but spatially variable with mean level of differentiation in the upstream section of the studied area being threefold higher (F ST = 0.0297) than observed in the downstream sector (F ST = 0.0100). Beside interannual water level fluctuation, 19 additional variables were considered and a multiple regression on distance matrices model (R (2) = 0.6397, P 0.001) revealed that water masses (b = 0.3617, P 0.001) and man-made dams (b = 0.4852, P 0.005) reduced genetic connectivity. Local level of interannual water level stability was positively associated to the extent of genetic differentiation (b = 0.3499, P 0.05). As water level variation impacts on yearly quality and localization of spawning habitats, our study illustrates how temporal variation in local habitat availability, caused by interannual water level fluctuations, may locally decrease population genetic structure by forcing fish to move over longer distances to find suitable habitat. This study thus represents one of the rare examples of how environmental fluctuations may influence spatial variation in the extent of population genetic structure within a given species.

Northern pike, Esox lucius, needs different habitats to survive and reproduce and thus depends on the availability and accessibility of these habitats. To efficiently manage pike, information is needed on its spatial and temporal patterns of migration. In this study, we investigated the occurrence of adult pike migration and which environmental variables influenced migration. From December 2010, we followed 15 pike for 1 year by use of radio telemetry in the River Yser, a typical lowland river characterised by anthropogenic impacts such as artificial embankments. Pike migrated most in February and March, which could indicate they frequented spawning habitat in this period. Four environmental variables significantly affected pike migration, ranging from the location where pike were observed (strongest effect), over water temperature and flow to diel water temperature change (weakest effect). The relation between migration and the location where pike were observed could demonstrate that pike preferred specific regions in the river. Increasing water temperature triggered migration for both sexes, and males started migrating at lower temperatures than females, which suggests that males start migrating earlier. This was the only substantial difference observed between male and female pike migration. The results suggest that migration was inhibited by high flow, as no migration was observed at high flow. River managers can use this information to efficiently manage their pike populations, for example, by removing or temporarily opening hydraulic structures like valves, weirs and sluices. This may facilitate access to suitable habitats at moments pike needs these habitats to fulfil its life cycle.

The combined effects of predators on prey may substantially differ from thatof each predator species alone because of alterations in prey behavior. Using enclosures within a pond, we examined experimentally the effects of two piscivorous predators on prey mortality and prey resource levels in two habitats. The two predators use two different foraging modes, which also allowed us to examine the behaviorally induced indirect effects of prey on predator growth and prey food resources. Both perch (Perca fluviatilis) and pike (Esox lucius) caused significant mortality of roach (Rutilus rutilus), and the combined predator mortality was higher than predicted from a multiplicative prey consumption model. Growth rates of perch were similar when enclosures contained only perch and when they contained perch combined with pike. The growth rate of pike was higher when they were together with perch compared to when alone. Growth of roach was similar among treatments. The invertebrate food resources of roach increased by a factor 10 in the open water but remained at similar levels throughout the experiment in the vegetation. Biomass of Daphnia longispina, the dominant zooplankton species in the open water, was strongly correlated with mortality of roach, indicating a density-mediated indirect effect of predators on prey resources. There was no indirect effect on D. longispina in the vegetation caused by habitat restriction of roach and only a weak relationship in the open water. There was a strong indirect effect of pike predation on macroinvertebrates induced by a habitat shift of roach. Our results suggest that there was facilitation between predators caused by conflicting antipredator behavior of roach, which resulted in density-mediated indirect effects on prey resources. The behavioral response of roach to the two predators also induced indirect effects on invertebrate prey.

International audience; Based on the analysis of 11 morphometric variables of body (total length, body area and perimeter, myotome height and eye diameter) and yolk sac (length, height, area, perimeter and volume) of pike larvae, the aim of this study was to evaluate how larval size at hatching and growth of larvae hatched from single egg batches vary according to three hatching times: early, mid and late. Hatching time structures strongly pike larval morphometrics. Early hatched larvae have smaller body sizes at hatch, faster growth and higher yolk use efficiency than late hatched ones. Early hatched larvae seem to be premature and hatch at precocious developmental stage whereas late hatched individuals continue their growth within the egg shell and hatch at larger size but with lower reserves (yolk). A compensatory growth phase was observed for the early hatching pike larvae particularly during the first 5days post hatch. Consequently, no significant difference in body parameters was recorded from day 10 post hatching whatever the hatching time. The higher growth accomplished by early hatched larvae may be related to a particular metabolic activity that converts more efficiently yolk into body tissues.

In a catch-and-release recreational fishery fish populations can be impacted by lethal and sub-lethal effects. In terms of sub-lethal effects anglers may directly (catch-and-release) and/or indirectly (angling-related disturbances, e.g. boating) influence the behaviour, growth and fitness of the fish. We quantified the long-term behavioural response of northern pike Esox lucius to angler-induced direct and indirect disturbances using radio-telemetry techniques. A whole lake experimental approach was conducted by dividing the study lake into an angling-disturbed and an angling-undisturbed lake side with 10 radio-tagged fish on each side, representing ~20% of the adult pike population. The impact of angling-caused disturbances on pike behaviour and growth as a proxy for fitness was assessed in a 7 month study period. Direct disturbances reduced swimming activities of pike and resulted in increased selection for structured (i.e., safer) habitat, whereas indirect disturbances had no significant effect on pike behaviour. Growth rates of caught-and-released fish were significantly smaller than those of uncaught pike (44%). Because, fish that were not captured by angling during the study period showed similar growth rates on both sides of the lake, this indicated that only direct angler-induced disturbances influenced pike growth. Our findings call for minimization of angling-related stressors during the process of catch-and-release angling to avoid behavioural and fitness impairments of the released fish because these may ultimately have population-level effects.

The vertical distribution, body orientation and mobility of pike free embryos were studied at 10 °C in 25-cm individual water columns. Five steps were identified: (1) a resting phase, up to day (D) 4 post-hatching; (2) an ascent phase (D1–D4); (3) a plateau (D5–D8), characterized by a wall-attachment behaviour in the subsurface zone; (4) a break-off phase (D9–D13); and (5) a final localization between mid-water and surface, corresponding to the air filling of the swim bladder and to the transition to active, horizontal swimming (D14–D17). Free embryos could be: side-lying (phase 1, late phase 4 and phase 5); lying upright (phases 4 and 5); vertically suspended with adhesion to the wall (phases 2–3 and early phase 4); and in oblique or horizontal position (phase 5). The opening of mouth and anus occurred during phases 2 and 3 and swim bladder filling started on days 13–14. Free embryo mobility was low and stable during the first 5 days and increased regularly thereafter to reach maximal levels on days 14–16. This research provides evidence for a more complex and more variable temporal pattern of free embryo vertical distribution, posture and mobility than previously thought. The vertical distribution, body orientation and mobility of pike free embryos were studied at 10 °C in 25-cm individual water columns. Five steps were identified: (1) a resting phase, up to day (D) 4 post-hatching; (2) an ascent phase (D1–D4); (3) a plateau (D5–D8), characterized by a wall-attachment behaviour in the subsurface zone; (4) a break-off phase (D9–D13); and (5) a final localization between mid-water and surface, corresponding to the air filling of the swim bladder and to the transition to active, horizontal swimming (D14–D17). Free embryos could be: side-lying (phase 1, late phase 4 and phase 5); lying upright (phases 4 and 5); vertically suspended with adhesion to the wall (phases 2–3 and early phase 4); and in oblique or horizontal position (phase 5). The opening of mouth and anus occurred during phases 2 and 3 and swim bladder filling started on days 13–14. Free embryo mobility was low and stable during the first 5 days and increased regularly thereafter to reach maximal levels on days 14–16. This research provides evidence for a more complex and more variable temporal pattern of free embryo vertical distribution, posture and mobility than previously thought., La répartition verticale, l’orientation corporelle et la mobilité de l’embryon libre de brochet ont été étudiées dans des colonnes d’eau individuelles de 25 cm à 10 °C. Cinq étapes ont été identifiées : (1) une phase de repos, pouvant durer jusqu’à 4 jours (J) après éclosion; (2) une phase ascensionnelle (J1–J4); (3) un plateau (J5–J8) caractérisé par un comportement d’adhésion à la paroi en subsurface; (4) une phase de rupture (J9–J13); et (5) une localisation finale entre la mi-profondeur et la surface, correspondant au remplissage de la vessie natatoire et au passage à une nage active dans le plan horizontal (J14–J17). Les orientations corporelles suivantes ont été observées : position allongée sur le flanc (phase 1, fin de phase 4, phase 5); position allongée sur l’abdomen (phases 4 et 5); suspension verticale avec adhésion aux parois (phases 2–3 et début de phase 4); et position oblique ou horizontale (phase 5). L’ouverture de la bouche puis de l’anus est intervenue au cours des phases 2 et 3 et le remplissage de la vessie natatoire a débuté à J13 ou J14. Le degré de mobilité de l’embryon libre, peu élevé et stable au cours des 5 premiers jours, a ensuite augmenté de façon régulière pour atteindre les valeurs les plus élevées entre J14 et J16. La présente étude met en évidence pour la répartition spatiale, la posture et la mobilité de l’embryon libre l’existence d’une séquence temporelle plus complexe et plus variable que ne le suggéraient les connaissances antérieures.

Esox lucius Linnaeus, 1758 Inland water: 30700-650 (1 spc.), 1974, B��y��k��ekmece Lagoon, Istanbul, N. Meri��., Published as part of Nurettin Meri��, L��tfiye Eryilmaz & M��fit ��zulug, 2007, A catalogue of the fishes held in the Istanbul University, Science Faculty, Hydrobiology Museum., pp. 29-54 in Zootaxa 1472 on page 37

Esox lucius Linnaeus, 1758 Inland water: 30700-650 (1 spc.), 1974, Büyükçekmece Lagoon, Istanbul, N. Meriç.