PCB and DDT levels were evaluated in populations of endemic Iberian barbel (Barbus bocagei) in the Jarama River in Spain via a pollution gradient from well-preserved areas upstream to contaminated downstream areas. Age structure, abundance, recruitment and levels of morphological abnormalities and ectoparasites were assessed. Upstream to downstream PCB concentrations ranged from 3.4 to 101.4 ng/g (ww) and from 0.9 to 19.6 ng/g ww for DDTs. The PCB pattern was dominated by the PCB 153, 138 and 180 congeners, and the less chlorinated ones had a relatively high contribution upstream. Barbels exposed to low PCB and DDT levels had a well-balanced population with a predominant cohort of young fish, indicating good recruitment. The most contaminated sites displayed a disrupted age distribution, where the proportion of young fish was clearly under-represented. Recruitment and total density of barbel populations decreased downstream where the highest PCB and DDT levels were found. In addition, a higher incidence of abnormalities and ectoparasites was observed at these sites. High concentrations of PCBs and DDTs most likely contribute to the reduction of Iberian barbel reproductive performance in the most contaminated sites, as shown by the disrupted age-distribution found in our study.
Keywords: DDTs; Freshwater fish; Iberian barbel; Organochlorine compounds; PCBs; Spain.
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