Sandimirov S. Heavy metal contents in whitefish (Coregonus lavaretus) along a pollution gradient in a subarctic watercourse. Environ. Monit. Assess. 2011, V. 182, №1-4, p. 301-316.

304 Environ Monit Assess (2011) 182:301-316 Table 1 Lake localities and distance to the pollution source (the Pechenganickel smelters) F Finland, N Norway, R Russia Lake no. Lake Country Geographic location Remoteness from the pollution source (km) 1 Kuetsjarvi R 69°27' N, 30°09' E 5 2 Skrukkebukta N 69°33' N, 30°07' E 16 3 Vaggatem N 69°13' N, 29°14' E 40 4 Rajakoski R 69°01' N, 28°55' E 65 5 Lake Inari F 68°50' N, 28°15' E 100 two different ecological morphs, differentiated by the morphology and number of gill rakers (Amundsen et al. 1999, 2004a; 0stbye et al. 2006). The densely rakered morph (hereafter referred to as DR whitefish) has numerous long and densely spaced gill rakers (approximately 30-40, mean number 33.0) and is predominantly feeding on zooplankton in the pelagic habitat, whereas the sparsely rakered morph (SR whitefish) has fewer, shorter and more widely spaced rakers (approx­ imately 20-30, mean number 23.1) and mainly reside in the littoral zone feeding on zooben- thos (Amundsen et al. 2004b). The two whitefish morphs exhibit distinct genetic and life-history differences (Amundsen 1988; Amundsen et al. 2004a, b ; 0stbye et al. 2006), and are treated as functional species in the analysis and presentation of the results. Field sampling and fish analyses Water, sediment and fish sampling was carried out during August and September 2004, with some additional heavy metal samples collected from fish in Skrukkebukta, Vaggatem and Rajakoski in September 2003 and 2005. Fish sampling was performed in the littoral (<8 m) and profundal (>10 m) habitats using bottom gillnets (1.5 m deep) and in the pelagic habitat (0-6 m) using floating nets (6 m deep). The gillnets consisted of eight 5-m sections with different mesh sizes (10, 12.5, 15, 18.5, 22, 26, 35 and 45 mm, knot to knot). The two whitefish morphs were identified from a visual evaluation of their gill raker morphology (Amundsen et al. 2004a). Each fish was measured for fork length and weight, sex and stage of mat­ uration were recorded, and otoliths were sampled for age determinations. Tissue samples were col­ lected from gills, liver, kidney and muscle of a subsample of fish for heavy metal analyses using stainless steel tools. The tissue samples (weight 3-10 g) were put into plastic sachets and frozen for further heavy metal analysis in the laboratory. A total of 3,117 whitefish were sampled from the five lake localities during the present study, whereas tissue samples for heavy metal analyses were collected from 244 fish. Age determination of whitefish was carried out by counting the hyaline zones of otoliths sub­ merged in glycerol using a stereo microscope with x 10-40 magnification. The somatic growth rate of the fish was modelled using von Bertalanffy’s growth model (Bagenal 1978; Roff 1984): L (t) = LTO(1 - e-Kt) (1) where L(t) is the mean fish length at age t, L x is the asymptotic length when age is close to infinity and K defines the rate at which the growth curve approaches the asymptote. These parame­ ters were estimated by non-linear regression, and the LTO estimates are used as a proxy for the growth performance of the different fish popula­ tions. Fish condition was assessed by calculating Fulton’s condition factor (FCF; Pyle et al. 2005): FCF = 100 x W /L 3 (2) where W is the weight in grams and L the fork length in centimetres. Furthermore, to explore the size and age at maturation, we used logistic regression with immature and mature fish as the nominal response variables to estimate the size at which 50% of the fish were sexually mature. As no major differences were found between the sexes, the presented results relate to the total fish populations. Springer