Stefan Skorić

Accumulation of 20 elements in great cormorant (Phalacrocorax carbo) and its main prey, common carp (Cyprinus carpio) and Prussian carp (Carassius gibelio).

In this study, 20 heavy metals and trace elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, Ni, Pb, Si, Se, Sr and Zn) were analyzed in different tissues (muscle, liver, intestine, feather and bone) of the great cormorant (Phalacrocorax carbo) and in different tissues (muscle, liver, gills, kidney and gonad) of their main prey (common carp-Cyprinus carpio and Prussian carp-Carassius gibelio) during the nesting season. Cormorant and fish specimens were collected at the Ečka Fishing Farm (Serbia) and from the nearby river. Principal components analysis (PCA) showed that cormorant livers were differentiated from other four tissues by higher concentrations of Hg, Fe, Cu and Mo, feathers by higher concentrations of Al and Si, and bones by higher concentrations of Sr and Mg. Differentiation among the three age classes of cormorants was observed only with regard to elemental concentrations in their feathers: subadult cormorants were differentiated by higher Hg and Zn concentrations, while the adults were separated by higher concentrations of Fe. In comparison with their prey (common carp and Prussian carp) cormorants were differentiated by higher concentrations of Fe, Hg and Cu in the muscle. Toxic mercury concentrations above 4μgg(-1)dw were determined in the liver of juvenile cormorants, as well as in the liver and feathers of subadults. Hg concentrations were significantly correlated among all studied tissues. Cormorant had significantly higher concentrations of Fe and Hg in muscle and liver than two studied fish species.

Use of histopathology and elemental accumulation in different organs of two benthophagous fish species as indicators of river pollution.

The bottom feeding fish species have a good potential to be used for assessments of pollution, as they are under pressure from pollutants from both water and sediments. In this study, the level of similarity of histopathological responses to pollution in gills and liver between barbel (Barbus barbus) and sterlet (Acipenser ruthenus) from the Danube River was assessed, and compared with elemental concentrations in their gills, liver, and muscle. Results indicate that the detected metal concentrations were likely cause of different tissue responses in gills and liver of the two investigated fish species. Statistical analysis indicated a clear differentiation of the two species based on elemental concentrations and the level of histopathological changes in gills and liver. Metal concentrations exceeded maximum acceptable concentrations in a number of analyzed specimens, which indicates the importance of this type of monitoring. Results indicate that barbel is a better indicator for specific, rather narrow sites, whereas sterlet is a better indicator of larger (longer) water current segments. Obtained information could be of importance for both scientists and fishery and water management authorities working on the development of water monitoring programs.

Age-specific metal and accumulation patterns in different tissues of nase (Chodrostoma nasus) from the Medjuvršje Reservoir.

Nase (Chodrostoma nasus L. 1758) specimens of four age classes (1(+) to 4(+)) were caught in July 2013 in the Medjuvršje Reservoir. Concentrations of 14 metals and elements (Al, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Si, Sr, Zn) in the muscle, gills and liver were analyzed by inductively-coupled plasma optical spectrometry (ICP-OES). The highest concentrations of Al, Ba, Co, Cr, Mn, Si, Sr and Zn were detected in gills, while Cd, Cu, Fe and Mo reached the highest values in the liver. The majority of the analyzed elements were found in minimal concentrations in the muscle. Younger age classes (1(+), 2(+)) were differentiated by higher concentrations of Mn, Sr and Zn in muscle tissue, while the older ones were mainly differentiated by higher concentrations for Ni and Cu. The youngest age class (1(+)) was distinguished by higher concentrations of Zn, while the oldest age class (4(+)) was distinguished by higher concentrations of Ba, Cu, Mo and Sr in gills. Results obtained were likely caused by differences in the physiology and feeding habits between younger (1-2(+)) and older (3-4(+)) age groups of nase.

Review of sterlet (Acipenser ruthenus L. 1758) (Actinopterygii: Acipenseridae) feeding habits in the River Danube, 1694–852 river km

The aim of this work is to present the variation in the sterlet’s (Acipenser ruthenus L. 1758) diet along the course of the River Danube, from 1694 to 852 river km. The diet of sterlet mostly comprised 12 bottom fauna taxa. Sterlet in the Danube feed mainly on larvae of Trichoptera, Chironomidae (Diptera) and Gammaridae (Amphipoda), with a reduction in food composition variability close to the Djerdap I dam and in the reservoir between the two dams. The other components of the diet were Corophium sp., Asselus sp., Mollusca, Oligochaeta, Annelida, Insecta, Nematoda and Hirudinea. The organisms typical of lithorheophilic and psammorheophilic biocoenoses play a considerable role in the diet of the sterlet. Composition of bottom fauna as food items varies due to changes in environmental conditions induced mainly by the construction of two dams: Djerdap I (943 river km, 1970) and Djerdap II (863 river km, 1984).

The geometric morphometrics and condition of Pontic shad, Alosa immaculata (Pisces: Clupeidae) migrants to the Danube River

Anadromous fish could have intraspecific groups with different life histories; identification of these is very important for management and conservation. Geometric morphometrics represents a quick and cost-effective method to identify such intraspecific groups. In this study, geometric morphometrics of Pontic shad (Alosa immaculata) migrants from the Danube River were investigated, as was Fultons condition factor (K), hepatosomatic index (HSI) and gonadosomatic index (GSI). Pontic shad specimens were collected during April and May of 2004 and 2006. The sample comprised four groups (65 males and 56 females in 2004; 110 males and 78 females in 2006). Geometric morphometrics revealed differences in shape that were statistically significant for both year (nested analysis of variance: F = 13.84; p < 0.001) and sex (nested analysis of variance: sex nested in year, F = 1.71; p < 0.01). The major differences between years were in head shape and position of fins. The most significant difference between females and males was in the dorsolateral expansion of the mid-body section with emphasis on the higher dorsal part of the body. Values for K in this work (0.65–0.70) were the lowest recorded for Pontic shad in the Danube River. Additional investigations involving both geometric morphometrics and molecular genetics are necessary to confirm the presence of races. This could be important information for conservation purposes as Pontic shad is listed as Vulnerable on the International Union for Conservation of Nature list.

Effects of mine tailing and mixed contamination on metals, trace elements accumulation and histopathology of the chub ( Squalius cephalus ) tissues: Evidence from three differently contaminated sites in Serbia

Chub (Squalius cephalus) specimens were collected in Korenita River seven months after spillover from the waste water of antimony mine tailing pond and compared with chub living in Kruščica reservoir (intended for water supply) and Međuvršje reservoir (influenced by intense emission of industrial, urban and rural wastewater). Concentrations of 15 elements (Al, As, B, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Si, Sr, Zn) were determined in muscle, liver and gills of chub by inductively coupled plasma optical spectrometry (ICP-OES) and histopathological alterations in liver and gills were assessed. Chub specimens from Korenita River had higher concentrations of As, Ba and Pb in all three investigated tissues as well as higher total histopathological index values than chub from reservoirs. Specimens from Međuvršje reservoir were characterized by higher values for concentrations of Cu and Si in muscle tissue and higher values for regressive histopathological alterations in gills. Individuals of chub from Kruščica reservoir had the highest concentrations of Fe in liver, Hg in muscle and Sr and Zn in muscle while gills had the lowest value of total histopathological index. The results from the present study showed higher level of histopathological alterations as a result of mine tailing accident. As a result of mixed contamination on the Međuvršje site, histopathological index values of gills were in line with the index value from Korenita River. Increased values for Fe and Sr in chub tissue from Kruščica reservoir could be explained by geological structure of the site which is characterized by magmatic rock rich in Cu, Fe and Ni as well as dominant carbonate sediment complex of marine origin with increased level of Sr.