Assessment of fish stocks and elemental pollution in the Danube, Sava and Kolubara rivers on the territory of the city of Belgrade, Serbia

Abstract

There is a lack of adequate estimates of the fish stocks in the Belgrade city area, Serbia, as well as of the current fishery pressure on fish diversity and of the contamination level of fish meat. These factors obstruct efforts to conduct valorisation of the current state and potential development of this resource. During 2012 and 2013, an assessment of the current state of the fish resources in Belgrade fishery waters was performed, in order to establish a good basis for the development of a monitoring system on the state of fish stocks and their exploitation. Fish were collected at ten localities in the Danube, Sava and Kolubara rivers. The fish stock composition and biomass were determined at each of the localities. The results indicate that the commercial fishery in the Danube and Sava rivers is characterised by seasonal variability regarding the amount and the composition of fish catch, while the ratio of high versus low quality fish remained relatively stable over time. In most of the analyzed fish, heavy metal concentrations remained below the prescribed maximum allowable concentrations (MAC). However, concentrations of mercury, cadmium and zinc exceeded MAC in the tissues of a number of individuals of Wels catfish, common carp, sterlet, pikeperch, European perch, ruffe, and sichel, which indicates that the meat of Danube fish species can be utilised in human diet only in limited quantities, and that it is necessary to establish permanent monitoring of heavy metal concentrations in this area. Based on the results, a system of indicators was defined and a monitoring system for the Belgrade fishery waters was proposed. Pikeperch and freshwater bream were selected as major species for fish meat quality monitoring, while the implementation of fishery monitoring program should comprise both economically important fish species and certain nonindigenous species.