Evidence for endocrine disruption in perch (Perca fluviatilis) and roach (Rutilus rutilus) in a remote Swedish lake in the vicinity of a public refuse dump.

A two-year study on perch (Perca fluviatilis) in Lake Molnbyggen, Sweden, located in a pristine area but with a public refuse dump in the vicinity, has been conducted. The mechanistic approach through a set of biomarkers during the first year included age, condition, somatic growth, liver, gonad, and spleen weights, and a number of other physiological variables, in addition to ethoxyresorufin O-deethylase, glutathione-S-transferase, glutathione reductase, catalase, and the formation of DNA adducts in the liver. Perch from the uncontaminated Lake Djursjön, located in a neighboring drainage area, were used as reference fish. The most pronounced effect was a 80% reduction in the gonadosomatic index (GSI) for females and a corresponding 36% reduction in males. Fin erosion and shallow open sores were also frequently observed. Biomarkers and later chemical analysis employed indicated that exposure to well-known environmental pollutants was low, suggesting that less well-known antrophogenic substances are responsible for the effects observed in perch from Lake Molnbyggen. During the second year, roach (Rutilus rutilus) of both sexes were also included in this study. In addition, aromatase (P450arom) activity in the brain and testosterone and 17beta-estradiol levels in blood plasma were analyzed. Only one-fourth of the female perch were found to be sexually mature, which was associated with decreased GSI, lower P450arom activity, and reduced circulating levels of steroids. The reproductive disorders observed indicates disturbed endocrine function(s), arresting the majority of the female perch in a sexually nonreproducible immature stage. This novel study is the first to report evidence for endocrine disruption in wild populations of fish living in a lake exposed to leakage water from a public refuse dump. Copyright 2001 Academic Press.