Survey of intersex condition in two species of wild fish exposed to multiple municipal wastewater discharges in the Grand River watershed

The Grand River watershed in Southern Ontario, Canada, is projected to experience population increases of 57% by 2031 with the majority of growth concentrated in urban centers (such as Kitchener – Waterloo, Guelph and Brantford) in the central portion of the watershed.  The 26 wastewater treatment facilities in this watershed represent the largest point source discharges to the Grand River, with many of the effluents released having constituents capable of producing adverse effects in exposed fish. Intersex condition, where female oocytes are found interspersed amongst the testicular tissues of male fish, represents a relevant whole organism biomarker of estrogenicity. To evaluate the extent and variability of intersex condition, a survey of 16 sites in the watershed was conducted by collecting resident Rainbow Darter (Etheostoma caeruleum) and Greenside Darter (Etheostoma blennioides). Male gonad samples were evaluated for the presence of primary oocytes using a new quantitative evaluation technique. Sampling was conducted in the fall of 2009 as well as the spring of 2010 indicated an increase in the occurence of intersex condition in resident darters at some sites receiving wastewater effluent.