FACTORS INFLUENCING ORGANOCHLORINE UPTAKE IN AGE-0 BROWN TROUT (SALMO-TRUTTA) IN LOTIC ENVIRONMENTS

In 1994 and 1995, we investigated the relationship between stream morp hology and water chemistry and levels of organochlorines (HCB, PCB, an d DDT) in young-of-the-year brown trout (Salmo trutta) from 25 streams in southern Sweden. Contrary to earlier findings for lakes, we found a positive relationship between trophic status (total phosphorus) and uptake of persistent pollutants in stream biota (trout). This differen ce between benthic, stream environments and pelagic, lake environments may be related to processes affecting pollutant uptake, i.e., polluta nt ''spiralling'' or the shift from heterotrophy to autotrophy in stre ams. Land use in the catchment area of the streams also affected pollu tant levels in trout, with higher levels in agricultural landscapes an d lower levels in forested areas. Size of catchment area, however, did not influence uptake of pollutants in trout. The results indicate tha t eutrophication of streams by agricultural activities and excessive n utrient loading may increase uptake of persistent pollutants in stream biota.