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Mercury is a highly toxic element for consumers, but its relation to amino acids and physiology of wild fish is not well known. The main aim of this study was to evaluate how total mercury content (THg) of northern pike (Esox lucius) is related to amino acids and potentially important environmental and biological factors along a climate-productivity gradient of ten subarctic lakes. Linear regression between THg and sixteen amino acids content [nmol mg−1 dry weight] from white dorsal muscle of pike from these lakes were tested. Lastly, a general linear model (GLM) for age-corrected THg was used to test which factors are significantly related to mercury content of pike. There was a positive relationship between THg and proline. Seven out of sixteen analysed amino acids (histidine, threonine, arginine, serine, glutamic acid, glycine, and aspartic acid) were significantly negatively related to warmer and more productive lakes, while THg showed a positive relationship. GLM model indicated higher THg was found in higher trophic level pike with lower cysteine content and inhabiting warmer and more productive lakes with larger catchment containing substantial proportion of peatland area. In general, THg was not only related to the biological and environmental variables but also to amino acid content. peerReviewed

The invertebrate fauna sampled on four locations (with an equal sampling effort performed on each locations) in the littoral area in the brackish water Lake Engervann on two dates (data report number of individuals sampled with the percentage contribution summed over two dates and combined for stations in the lower (Lower %) and upper sections (Upper %), and for the four sites and two dates combined in last column (Total %) (all data are taken from Halvorsen et al. [1]. Sampling sites 1 and 2 are from the lower and southern section on each side of the lake while site 3 and site 4 is situated on each side in upper northern part of the lake (see Fig. 1). (PDF 199 kb)

DAPC analyses (Dicriminant analysis of principal components) in adegenet (Jombart 2008) performed on the three lateral plate morphs of threespine stickleback from Lake Engervann. (PDF 299 kb)

STRUCTURE-HARVESTER results for the Lake Engervann sticklebacks. (PDF 640 kb)

The invertebrate fauna sampled on four locations (with an equal sampling effort performed on each locations) in the littoral area in the brackish water Lake Engervann on two dates (data report number of individuals sampled with the percentage contribution summed over two dates and combined for stations in the lower (Lower %) and upper sections (Upper %), and for the four sites and two dates combined in last column (Total %) (all data are taken from Halvorsen et al. [1]. Sampling sites 1 and 2 are from the lower and southern section on each side of the lake while site 3 and site 4 is situated on each side in upper northern part of the lake (see Fig. 1). (PDF 199 kb)

STRUCTURE-HARVESTER results for the Lake Engervann sticklebacks. (PDF 640 kb)

DAPC analyses (Dicriminant analysis of principal components) in adegenet (Jombart 2008) performed on the three lateral plate morphs of threespine stickleback from Lake Engervann. (PDF 299 kb)

Summary statistics of stable isotopic values of putative prey items for the threespine stickleback sampled in the brackish water Lake Engervann and marine areas. (PDF 176 kb)

A table of other fish species in the sampled localities. All the Norwegian minnow (Phoxinus phoxinus) populations used in the study and the other fish species in the same locality. The species of fish are: AC = Arctic charr (Salvelinus alpinus) BL = bleak (Alburnus alburnus), BR = bream (Abramis brama), BT = brown trout (Salmo trutta), BU = burbot (Lota lota), CC = crucian carp (Carassius carassius), CH = chub (Leuciscus cephalus), EE = eel (Anguilla anguilla), GR = grayling (Thymallus thymallus), PE = perch (Perca fluviatilis), PI = pike (Esox lucius), RU = ruffe (Gymnocephalus cernuus), SS = Siberian sculpin (Cottus poecilopus), VE = vendace (Coregonus albula), WB = white bream (Blicca bjoerkna), WF = European whitefish, SM = smelt (Osmerus eperlanus), ID = ide (Leuciscus idus), DA = dace (Leuciscus leuciscus), 9-SB = nine-spined stickleback (Pungitius pungitius) and 3-SB = tree-spined stickleback (Gasterosteus aculeatus). (DOC 192 kb)

Figure of distribution of Gyrodactylus spp. individuals. Distribution of Gyrodactylus spp. individuals in the total dataset of 1278 individual minnows (Phoxinus phoxinus) hosts from 43 populations in Norway. Here the 14 native and 23 stocked populations have been pooled. On the left axis is the probability of occurrence and on right axis is given counts. (DOCX 76 kb)

A table of tests result of demographic bottleneck. All the Norwegian minnow (Phoxinus phoxinus) populations used in the study. Information from tests of demographic bottleneck using Bottleneck 1.2.0.2. (Piry et al. 1999) with the two-phase model (TPM) and the Wilcoxon sign-rank test, and demographic expansion (where the intra-locus k-test identify signals of recent population expansion, while the inter-locus g-test identify signals of more ancient population expansion) using Kg-test (Reich et al. 1999). Footnotes: *Samples used in the rarefaction analysis using EstimateS 8.2.0 (Colwell 2011) where more than 5 Gyrodactylus spp. individuals were observed in the population. This number of observed Gyrodactylus spp. individuals is needed to calculate rarefaction in EstimateS 8.2.0. # None of tests were significant. (DOC 116 kb)