The study on medium size river Sutla in Croatia indicated considerable water contamination at specific sites during the baseflow period, probably associated to low flowrate (0.73-68.8 m 3 s -1 ), and consequently low dilution capacity of this river. Various aspects of contamination were observed: increased conductivity to 1,000 lS cm -1 , decreased dissolved oxygen level to 50%, 4-5°C increased water temperature, increased concentrations of several dissolved trace elements (e.g., maximal values of Li: 45.4 lg l -1 ; Rb: 10.4 lg l -1 ; Mo: 20

No abstract

Diploid (2n) and triploid (3n) coho salmon were fed upon control (diet 1), recombinant porcine somatotropin (rpST)-supplemented (diet 2; 20 μg rpST/g body wt/day) or rpST/antacid/detergent-containing feed (diet 3; 20, 100 & 20 μg/g body wt/day respectively) for 16 wk. Fish were weighed and measured bimonthly and their relative performances assessed. By wk 4, 2n and 3n groups fed upon diet 2 were significantly heavier and longer than control 2n fish. At the termination of the trial, diet 3 fed animals were greater in weight than all other treatment groups. Diet 3 salmon also returned better feed conversion efficiencies than either diet 1 or 2 groups. RpST therapy induced a 28.7% and 60.2% increase in group wt for 3n diet 2/3 coho versus (-vs-) controls. Likewise, 2n rpST-treated fish increased wt -vs-2n control coho by 17% and 50% respectively over the same period. No differences were recorded between groups for body moisture, but diet 2, 3n and both diet 3 groups exhibited decreased condition factors when compared to control fish (p ≤ 0.05).

The study of metal bioaccumulation in the gills of European chub (Squalius cephalus) was conducted in September 2009 at the medium-sized rural river Sutla, characterized by agricultural and municipal type of water contamination. The concentration ranges were established for the first time in the soluble, metabolically available fractions of chub gills for 12 metals, which are environmentally extremely relevant and yet only seldom studied, as follows in a decreasing order: K, 225-895 mg L(-1); Na, 78-366 mg L(-1); Ca, 19-62 mg L(-1); Mg, 13-47 mg L(-1); Rb, 164-1762 μg L(-1); Sr, 24-81 μg L(-1); Ba, 13-67 μg L(-1); Mo, 1.3-16 μg L(-1); Co, 0.7-2.7 μg L(-1); Li, 0.4-2.2 μg L(-1); Cs, 0.2-1.9 μg L(-1); and V, 0.1-1.8 μg L(-1). The concentrations of Fe (1.6-6.4 mg L(-1)) and Mn (16-69 μg L(-1)) were also determined and were in agreement with previous reports. By application of general linear modelling, the influence of different abiotic (metal exposure level) and biotic parameters (fish sex, age, size and condition) on metal bioaccumulation was tested. It was established that bioaccumulation of many metals in fish depended on various physiological conditions, wherein Ba could be singled out as metal exhibiting the strongest association with one of biotic parameters, being significantly higher in smaller fish. However, it was also undoubtedly demonstrated that the concentrations of three metals can be applied as reliable indicators of metal exposure even in the conditions of low or moderate water contamination, such as observed in the Sutla River, and those were nonessential elements Li and Cs and essential element Fe. The results of our study present an important contribution to maintenance of high ecological status of European freshwaters, through enrichment of knowledge on the bioaccumulation of various metals in gills of European chub as frequently applied bioindicator species in monitoring of water pollution.

26The assessment of general condition of fish in the moderately contaminated aquatic environment was performed 27 on the European chub (Squalius cephalus)