Mercury and Methylmercury Concentrations in Muscle Tissue of Fish Caught in Major Rivers of the Czech Republic

The aim of the study was to evaluate mercury contamination at twelve outlet sites of rivers in the Czech Republic (Labe, Ohře, Vltava, Berounka, Sázava, Otava, Lužnice, Svratka, Dyje, Morava and Odra). As an indicator, we used muscle tissue of the chub (Leuciscus cephalus) caught at selected sites in 2007. A total of 96 fish were examined. Total mercury was determined by atomic absorption spectrophotometry using the AMA 254 analyzer and methylmercury was determined by gas chromatography with electron-capture detection. Total mercury (THg) and methylmercury (MeHg) concentrations ranged 0.039–0.384 mg kg-1 fresh weight and 0.033–0.362 mg kg-1 fresh weight, respectively. Mercury bound in methylmercury (HgMe) made up on average about 82.2% of total mercury. The highest mercury concentrations were found in fish from Obříství, a site on Labe (THg 0.263 ± 0.086 mg kg-1; MeHg 0.256 ± 0.084 mg kg-1). Mercury concentrations in fish from rivers that cross the borders of the Czech Republic (Labe, Odra and Morava) were low. The Czech Republic therefore does not contribute significantly to river pollution outside its national borders. Hazard indices of the sites monitored were well below 1, and reached 1.365 only in Obříství on Labe for fisherman’s family members (i.e. in the case of annual consumption of 10 kg fish). This indicates possible hazards involved in eating meat of fish caught in that location. Based on PTWI for methylmercury, the maximum amount of fish meat allowed for consumption per week was calculated. The site with the lowest value was Obříství on Labe (0.44 kg). The results of this study present a partial contribution to health risk assessment on the major rivers in Czech Republic

Arsenic Content in Tissues of Fish from the River Elbe

The aim of the study was to evaluate arsenic content in tissues (muscle, liver, kidneys, gonads) of fish caught in selected localities along the River Elbe and its tributary the Vltava in 1999, 2002 and 2003, and in pools of the River Elbe in 2000. A total of 118 bream and 151 perch were examined by AAS. The highest muscle tissue arsenic concentrations were found in Zelãín in bream in 2003 (0.17 ± 0.08 mg·kg-1) and in perch in 2002 (0.084 ± 0.012 mg·kg-1). The highest arsenic concentrations in perch were found in the kidneys, followed by the liver, milt, muscle tissue and eggs. An increase (P < 0.01) in arsenic concentrations in 2003 (after floods) compared with 2002 was found in bream muscle tissues in Zelãín and in perch muscle tissues in Podolí; a decrease in arsenic concentrations was demonstrated in perch musculature in Verdek, Nûmãice, Hfiensko (P < 0.01) and in bream musculature in Hfiensko (P < 0.05). Arsenic contamination in the localities under study does not pose a major environmental or health risk. River Vltava, Elbe pools, bream, perch, As distribution, AAS Arsenic is brought to the environment through natural and anthropogenic routes. The most serious sources of arsenic pollution include emissions and waste water of the ore mining and processing industry, dye manufacture facilities, tanneries, and also thermal power plants, application of certain insecticides, herbicides, etc. Because arsenic accompanies phosphorus, it is also found in wash water. Arsenic has a considerable tendency to accumulate in bottom sediments (Pi t ter 1999). For that reason, issues relating to arsenic content in aquatic organisms, and sea fish in particular, have attracted considerable attention (Lai et al. 2001). A number of recent studies have dealt with arsenic compounds speciatio

EFFECT OF CULTURE CONDITIONS ON REPRODUCTIVE TRAITS OF BROWN TROUT SALMO TRUTTA L.

Progeny from artificial propagation of wild brown trout (Salmo trutta L.) of the Blanice river, Czech Republic, were farmed to maturity and spawned at ages three, four and five during 2002-2004. Reproductive parameters and biological quality of eggs in this farmed population were compared to those of the original wild population. ANCOVA showed no differences between wild and farmed fish in weight of eggs per female, total fecundity, or relative fecundity in any year. Significantly higher egg diameter (4.57 mm, P = 0.001) and weight (69.3 mg, P = 0.0375) were found in the wild population in 2002 and conversely in 2004, the mean egg weight was higher in the farmed population (94.7 mg, P = 0.0021). Differences in egg diameter in this year (4.64 ± 0.06 and 4.82 ± 0.06 in wild and farmed trout, respectively) were close to the level of significance (P = 0.079). Mutual correlations between length or weight and studied reproductive traits were similar in both populations. Fertilization rate, duration of incubation period, egg losses during incubation and mortality of starving hatched fry were monitored in embryos and larvae of farmed population only (FxF), crosses between farmed females and wild males (FxW) and wild population only (WxW). Altogether 6.3%, 5.8% and 5.4% of eggs died during incubation period in FxF, FxW and WxW, respectively. There were also no significant differences in duration of incubation period and mortality of starving fry. It can be concluded that farming conditions did not significantly affect the reproductive parameters and quality of eggs in the first generation of farmed broodstock

EFFECT OF CULTURE CONDITIONS ON REPRODUCTIVE TRAITS OF BROWN TROUT SALMO TRUTTA L.

Progeny from artificial propagation of wild brown trout (Salmo trutta L.) of the Blanice river, Czech Republic, were farmed to maturity and spawned at ages three, four and five during 2002-2004. Reproductive parameters and biological quality of eggs in this farmed population were compared to those of the original wild population. ANCOVA showed no differences between wild and farmed fish in weight of eggs per female, total fecundity, or relative fecundity in any year. Significantly higher egg diameter (4.57 mm, P = 0.001) and weight (69.3 mg, P = 0.0375) were found in the wild population in 2002 and conversely in 2004, the mean egg weight was higher in the farmed population (94.7 mg, P = 0.0021). Differences in egg diameter in this year (4.64 ± 0.06 and 4.82 ± 0.06 in wild and farmed trout, respectively) were close to the level of significance (P = 0.079). Mutual correlations between length or weight and studied reproductive traits were similar in both populations. Fertilization rate, duration of incubation period, egg losses during incubation and mortality of starving hatched fry were monitored in embryos and larvae of farmed population only (FxF), crosses between farmed females and wild males (FxW) and wild population only (WxW). Altogether 6.3%, 5.8% and 5.4% of eggs died during incubation period in FxF, FxW and WxW, respectively. There were also no significant differences in duration of incubation period and mortality of starving fry. It can be concluded that farming conditions did not significantly affect the reproductive parameters and quality of eggs in the first generation of farmed broodstock

Recapture and condition of pond-reared, and hatchery-reared 1 + European grayling stocked in addition to wild conspecifics in a small river

The relative performance of European grayling Thymallus thymallus reared in a hatchery on commercial dry feed or in a pond with natural food and their wild conspecifics, was assessed through recapture of tagged fish 5 months after their release into the Blanice River, Czech Republic. One-year old pond and hatchery reared fish from a resident broodstock were marked using Visible Implant Elastomer tags and released into 3 sections of river in May 2006. Wild one-year-old grayling were also tagged in these sections on the same days. The ratio of hatchery reared, pond reared, and wild fish was 1:1:1 in all sections. The recapture rate (hatchery 14.9%, pond 22.1%, and wild 51.3%) and site fidelity (hatchery 7.8%, pond 13.0%, and wild 35.1%) were significantly different among groups. Wild fish had a higher probability of recapture upstream of their original section than did hatchery or pond reared fish. Pond rearing was superior to conventional hatchery rearing for subsequent stocking of 1 +  grayling in running water. Initially different mean condition factors were similar in all groups at recapture, suggesting adaptation of the artificially reared fish that remained in the river sections surveyed