MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(VER-1117-803938) Endocrine disruption in natural fish populations in Belgium.

Versonnen, B¹, De Coen, W², Janssen, C³, ¹ Euras, Ghent, Belgium² University of Antwerp, Antwerp, Belgium³ Ghent University, Ghent, Belgium

ABSTRACT- Since the observation of higher incidences of intersex in fish living in waters receiving effluents from sewage treatment works (STWs), effects of estrogenic compounds in the environment have been widely studied. However, to date no information was available on the occurrence of endocrine disruption in natural fish populations in Belgium (Western Europe). Moreover, in the very densely populated (440 inhabitants/km²) northern part of Belgium only 57 % of the household sewage water is treated prior to release in surface waters. Compounds with estrogenic activity are thus likely to occur in the surface waters. Therefore, we sampled, over a 3-year period, 797 roach (Rutilus rutilus), rudd (Scardinius erythrophtalmus) and tench (Tinca tinca) in 12 rivers, canals and ponds in Flanders (northern Belgium). Different conditional and endocrine parameters of these fish were measured: condition factor (CF), gonadosomatic index (GSI), blood or plasma vitellogenin (VTG) content and gonad histology. Elevated VTG levels in blood plasma were detected in fish collected at 2 sampling stations, 25 % of the male roach sampled for histology showed signs of intersex: 2 - 80 primary oocytes per testis slice in most fish and completely affected gonads in one fish. Further, degraded, vacuoled oocytes were observed in severely affected fish and overall sex-ratios of roach were skewed towards females. These results are compared with calculated and measured concentrations of natural hormones (excretions by cattle, human population) and other endocrine disrupters. The findings suggest that endocrine disrupting compounds are present in surface waters in Flanders in concentrations that adversely affect roach populations. However, compared with some of our neighbouring countries the effects observed appear less severe.

Key words: endocrine disruption, natural populations, fish, roach