Contaminants in the Baltic Herring
PCB, DDT compounds and Hg have a clear dependence on the age in the female Baltic Herrings.
The Finnish Institute of Marine Research has been analysed heavy metals and organic contaminants from different age classes of the Baltic Herring at five sampling locations in the Gulf of Finland and the Gulf of Bothnia since year 1997 (see map in Figure 1). Annually herrings have been analysed from one catchment area to follow the accumulation of contaminants. Sampling of herrings was performed always in autumn.
Heavy metals (Cd, Hg, Pb, Cu, Zn) have been measured in muscles homogenates in1997-2001 and in individual livers and muscles in 1999-2001.
Organic contaminants were analysed from the freeze-dried homogenates of several individuals from herrings collected between 1979 and 1999. Since 2001 fresh individuals have been analysed without freeze-drying.
Figure 1. Map of the sampling locations
Data on heavy metals in the individual herrings is presented in Figure 2. Increasing trend of Hg concentrations was found in the older herrings at every study areas in the both homogenates and individual samples. For Cd not similar trend was observed. At some stations (e.g. Kalajoki, Åland) Cd concentrations seem to stabilised after 10 year, while in Hanko area increased Cd values were found until 10 year and after that decreased concentrations. Thus there is no common Cd concentration trend in the dataset.
Concentrations of Cd and Pb were very low (near the detection limit) from the muscles homogenates, so liver samples were measured as well. However, Pb concentrations in livers were also low and no trend was observed in the results. Also, for Zn and Cu concentrations no clear trend was found. The study shows that only Hg seems to have correlation with the herring age.
Figure 2. Examples of cadmium (Cd, average of individual livers) and mercury (Hg, average of individual muscles) data in different age classes of female Baltic Herring in three sampling areas in 1999-2001.
All the data concerning organic pollutants shows a very clear age dependence of studied substances (Figure 3). The amount of contaminants in the ten year old herrings was about five-fold compared to two years old ones. Anyhow the accumulation rate seems to be slower after eight years.
Figure 3. Examples of CBs and DDTs in muscle homogenates of different age classes of female Baltic Herring.
PCB= sum CB(28,52,101,118,138,153 and 180), DDT= sum pp’DDE, pp’DDD and pp’DDT).
The study indicates that the concentrations of PCB and DDT compounds and Hg depend on age in a predictable fashion. This confirms the earlier findings that the fat-soluble contaminants tend to enrich in the old fish. It also indicates that the regular monitoring programme targeted in one age class only seems to represent adequately the annual situation in the study areas. Thus our conclusion is that it is not necessary to continue the measurement of the age-dependency of contaminant concentrations on an annual basis. Additionally, it is questionable how well the older individuals represent their respective catchment areas as herrings migrate in the different parts of the Baltic Sea.
More information on the age-dependency of contaminants will be obtained by an on-going EU-funded project for studying dioxin compounds in fish of the Baltic Sea coordinated by National Food Agency in Finland. Beside dioxin compounds, several other contaminants (i.e. heavy metals) are studied widely in the different fish species, age classes and areas of the Baltic Sea. Also several other scientists have studied age classes of herring in the Baltic Sea (e.g. Kiviranta et al. 2003).
Thus the additional national monitoring programme of the age classes has been ended 2002. Regulatory monitoring programme will, of course, be continued.
Kiviranta H, Vartiainen T, Parmanne R, Hallikainen A, Koistinen J. 2003. PCDD/Fs and PCBs in Baltic herring during the 1990s. Chemosphere 50:1201-1216.
Page updated 7 October 2003