Mirjana Lenhardt

Liver, gills, and skin histopathology and heavy metal content of the Danube sterlet (Acipenser ruthenus Linnaeus, 1758).

The sterlet (Acipenser ruthenus L.) is a bottom-feeding fish species with a direct exposure to contaminants from water and sediments. Although heavy metal pollution is believed to be one of the main threats to the sterlet population in the Danube River basin, there is a lack of knowledge of the exact impact of heavy metals on their survival. In the present study, effects of heavy metal pollution on sterlet in the Danube basin were assessed as well as the utility of different sterlet organs and tissues as indicators of heavy metal contamination. The sterlet were sampled at three different sites in the Danube basin, in Hungary and Serbia, isolated from each other by dams. Heavy metal analysis included measurement of Cd, As, Pb, Cr, Hg, Cu, Ni, Fe, Mn, and Zn concentrations in sterlet gills, muscle, liver, and intestine, and histopathological analyses comprised assessment and scoring of the extent and intensity of alterations in skin, gills, and liver tissue. Analysis revealed a significant presence of sublethal histopathological changes that were most pronounced in the liver and skin and increased accumulation of heavy metals, with the highest concentrations in the liver. Canonical discriminant analysis showed significant differentiation among the three studied localities, suggesting that the heavy metal concentrations in sterlet populations were site specific. The present study concludes that the accumulation of heavy metals is a response to the presence of these pollutants in the environment, and, together with other pollutants, it affects the vital organs of natural sterlet populations.

Heavy metal accumulation and the genotoxicity in barbel (Barbus barbus) as indicators of the Danube river pollution.

The aim of this study was to analyze 16 trace elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, and Zn) in different barbel (Barbus barbus) tissues and to detect the presence of genotoxic effects in erythrocytes with the alkaline comet assay. Barbel specimens were collected in the Danube river near Belgrade, Serbia, where the discharge of untreated communal and industrial wastewaters is likely to produce negative effects on fish residing in this area. The highest concentrations of Sr, Mn, Fe, Ba, B, and Al were found in gills, Mo and Cu in liver, and As and Zn in gonads. Concentrations of Zn and Fe were above maximum acceptable concentrations (MACs) in a number of gonad, gill, and liver samples. Three-year-old barbel specimens had higher tail moment and Zn concentrations in gills (1.71 and 51.20 μg/g dw, resp.) than 5-year-old specimens (0.85 and 42.51 μg/g dw, resp.). Results indicate that the younger barbel specimens might be more suitable for the monitoring of environmental pollution.

Non-native and translocated fish species in Serbia and their impact on the native ichthyofauna

A total of 22 fish species have been introduced into the inland waters of Serbia, either intentionally or accidentally. This paper provides a summary of data concerning time and reason of introduction, mode of expansion, degree of acclimatization, impact on native fish and estimated area of recent distribution. Four of the non-native fish species currently occupy more than 51% of Serbian territory while 5 of them occupy between 21–50% of territory. This paper reviews impacts of introduced freshwater fish in Serbia based on collected data.

Assessment of Extinction Risk and Reasons for Decline in Sturgeon

Sturgeon populations in the Danube River have been affected by a combination of hydropower development, over-harvesting, habitat degradation from agricultural and industrial practices and from urbanization. The effects of these changes have been monitored on six sturgeon species inhabiting the Danube River. Two of them are resident species, while the other four migrate to the river for spawning. Atlantic sturgeon (Acipenser sturio) has completely disappeared from this region. Ship sturgeon (Acipenser nudiventris) is very rare in professional fishing catches. Beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus) are endangered with different levels of extinction risk. Here, we model the time dependence of the beluga and Russian sturgeon catch in the Serbian part of the Danube River. Predicted extinction of Russian sturgeon was estimated to fall around the middle of the century, and for beluga approximately at middle of the millennium. Suggestions for sturgeon conservation measures on a national level and coordination of all relevant institutions in Serbia are also presented.

Population viability analysis of the Danube sturgeon populations in a Vortex simulation model

Populations of six sturgeon species in the Danube River (beluga, Russian sturgeon, stellate sturgeon, sterlet, ship sturgeon and Atlantic sturgeon) have experienced severe decline during the last several decades, mostly due to the unsustainable fishery, river fragmentation and water pollution. Present lack of knowledge on basic sturgeon demography, life history and relative effects of different negative factors is further hindering implementation of efficient policy and management measures. In the present study, population viability analysis in a Vortex simulation model has been conducted in order to assess the state of the six Danube sturgeon species, their future risk of extinction and to determine the most suitable conservation and management measures. Population viability analysis has revealed a large sensitivity of the Danube sturgeon populations to changes in the natural mortality, fecundity, age at maturity and spawning frequency. It was also confirmed that the sturgeons are highly susceptible to even moderate levels of commercial fishery, and that their recovery is a multi-decadal affair. Stocking with adult individuals was shown to produce considerably greater effect on population persistence than stocking with juveniles, but the latter approach is probably still preferable since it avoids many inherent problems of aquaculture cultivation. This study represents the first population viability analysis of the Danube sturgeons.

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.

Distribution and accumulation of elements (As, Cu, Fe, Hg, Mn, and Zn) in tissues of fish species from different trophic levels in the Danube River at the confluence with the Sava River (Serbia)

Pikeperch (Sander lucioperca), European catfish (Silurus glanis), common carp (Cyprinus carpio), and gobies (Neogobius gymnotrachelus, Neogobius melanostomus) were collected from the Danube River (Belgrade section), and samples of liver, muscle, or whole-body composites (in the case of gobies) were analyzed for As, Cu, Fe, Hg, Mn, and Zn with inductively coupled plasma optical spectrometry to find out if there was a correlation between accumulation of these elements in predatory and prey species, as well as in pairs of species with overlapping diets. Concentrations of all analyzed elements were either higher (Cu, Fe, Mn, Zn) in liver than in muscle, or equal (As, Hg), except for Hg in carp, which was higher in muscle. Mercury concentration in liver and muscle of predators (catfish, pikeperch) was significantly (<10−4) higher than in prey fishes (carp and gobies). The results indicate that Hg concentration was biomagnified through the food chain. Concentrations of As, Fe, and Hg in carp liver and gobies whole-body composite were similar, but carp had significantly (<10−4) higher values of Zn and Cu in liver. The regression analysis and trendline equations indicate that the concentrations of all tested elements, except for As in liver, and Mn and Fe in muscle, were similar in predatory fish (pikeperch and catfish), on one hand, and in prey fish (carp and gobies), on the other hand. Distinctly high Zn concentration in carp is very common in this species due to its physiology. Concentrations of Hg and Zn were higher than the maximum acceptable concentration due to the high pollution level in this section of the Danube River, accordingly posing a risk for the human consumption of these fish species.

A report of Eriocheir sinensis (H. Milne Edwards, 1854) [Crustacea: Brachyura: Grapsidae] from the Serbian part of the Danube River

Two specimens of the Chinese mitten crab, Eriocheir sinensis, were found in the Serbian part of the Danube River (1995, 1084

Trends in Fisheries Science from 2000 to 2009: A Bibliometric Study

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Flooding modifies the genotoxic effects of pollution on a worm, a mussel and two fish species from the Sava River

km of the watercourse and 2001, 1174