Linear Growth of Sparsely Rakered Whitefish Coregonus lavaretus (Coregonidae) of the Imandra Lake (Murmansk Oblast) / Zubova E. M., Kashulin N. A., Terent’ev P. M. [et al.] // Journal of Ichthyology. – 2016. - Vol. 56, №. 4. - P. 588–599

Table 1. Characteristics of the used materials 590 ZUBOVA et al. Region Period of studies Number of fish, spec. Bolshaya Imandra Lake September-October 2012-2013 46 (Belaya Bay, Mogil’nyi Island) Yokostrovskaya Imandra Lake August-September, 2011, every month 463 (Uzkaya Salma Channel, Bolshoi Yokostrovskii Island) from July to April 2012-2013 Babinskaya Imandra Lake August-September 2011 140 (Kunchast Bay, Khort Island) enabled the catching of individuals that were >5 cm long. In the littoral zone (at a depth of 1.5—3.0 m), one or two nets were installed perpendicular to the shore in the places with sand and gravel shoals and large boul­ der depositions. In the profundal zone with depths greater than 18 m, up to ten different-cell nets were used in the same order. In the pelagic zone of the pond, floating multisized nets with a height of 3 m were used. A sum of 649 whitefish specimens caught in different regions of the Imandra Lake was studied for the period of 2011—2013 (Table 1). Hydrochemical and hydrobiological samples were taken during the hydrobiological summer (July—August) in the places where ichthyologic samples were collected (Fig. 1). A biological analysis was made according to stan­ dard methods (Pravdin, 1966; Sidorov and Reshet- nikov, 2014). The weight of fish was determined to an accuracy of 1 g, and the length was measured accord­ ing to Smith (FL) to an accuracy of 1mm. To mark out the intraspecific forms in the studied whitefish, rakers were counted on the first gill arch (Reshetnikov, 1980; Siwertsson et al., 2008). To determine the age and rate of linear growth, scale was examined in 636 whitefish specimens (2011—2013). Scale was always taken from the same area—under the frontal part of the dorsal fin (Zinovyev and Mandritsa, 2003); the measurements were all made by the same operator. The growth rate was calculated using the Lee for­ mula according to the diagonal radius of scale (Bryuzgin 1969, Mina, 1973, 1981; Zubova, 2015). The growth rate was characterized using both absolute increases and a specific growth rate calculated by the Schmalhausen-Brodie formula (Schmalhausen, 1935; Mina and Klevezal, 1976; Dgebuadze, 2001; Smet- anin, 2003). Hydrochemical parameters were determined at the laboratory of the Center for Collective Use of the Institute of the Industrial Ecology Problems of the North at the Kola Scientific Center of the Russian Acad­ emy of Sciences (certificate of accreditation of the test laboratory (center) no. ROSS RU.0001.517126). The gross concentrations of heavy metals and aluminum that are priority pollutants in the Kola Region were determined in water and bottom sediment samples by atomic absorption spectrophotometry (Antropogennye modifikatsii..., 2002). Sampling, chamber treatment and analysis of phytoplankton, zooplankton, and macrozoobenthos samples were carried out according to conventional standard methods (Rukovodstvo ..., 1992; Denisov, 2011). RESULTS AND DISCUSSION Hydrochemical and hydrobiological indicators of three Imandra Lakes are different: there is a trend towards growth in their values from the conventionally background Babinskaya Imandra Lake to the polluted Bolshaya Imandra Lake (Table 2). After the anthropo­ genic load on the Imandra Lakes decreased in 1993— 2000 (Antropogennye modifikatsii ..., 2002), today there is some decrease in the water concentration of major pollutants, such as copper and nickel, in comparison with the period when the pollution of the lakes was maximal (Fig. 2). Meanwhile, the content of these ele­ ments in the surface bottom sediment layer (0—1 cm) has currently grown (Fig. 3). The current concentra­ tions of copper, nickel, and strontium in water and in the surface bottom sediment layer in all the Imandra Lakes surpass the background values (Table 2), which indicates the persistent high level of anthropogenic load on the pond. The high indicators of primary pro­ duction, zooplankton, and macrozoobenthos corre­ spond to the high content of biogenic elements (total phosphorus and nitrogen) in the Yokostrovskaya and Bolshaya Imandra lakes. The trophic status of these lakes is detected to vary from the mesotrophic to hyper-eutrophic status; only the water of the Babinskaya Imandra Lake is close to the natural state and corresponds to the oligotrophic trophic status. Intraspecific Forms and Composition o f Whitefish Catches The studies, which were carried out in the period of the maximum pollution of the Imandra Lakes, did not mark out the intraspecific whitefish forms. Our catches in the Babinskaya Imandra contained only one whitefish form: sparsely rakered whitefish (a ben- thophage); the catches in the Yokostrovskaya and Bol- shaya Imandra lakes contained two forms: sparsely and densely rakered whitefish (Table 3). The latter form (planktophage) in these two lakes was 1 and 30% of the whitefish catches. The presence of densely rak- ered whitefish in the Yokostrovskaya and Bolshaya JOURNAL OF ICHTHYOLOGY Vol. 56 No. 4 2016