2012/01/01 by Joyce Evans, Leland J. Jackson, Hamid R. Habibi +1 · 1 citation
Environmental Science · Biochemistry, Genetics and Molecular Biology · #Fish Ecology and Management Studies #Reproductive biology and impacts on aquatic species #Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities
paper · pdf · doi:10.6064/2012/521931
openalex publication_date 2012/01/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We sampled an abundant, native minnow (Longnose dace-Rhinichthys cataractae) throughout the Oldman River, Alberta, to determine physiological responses and possible population level consequences from exposure to compounds with hormone-like activity. Sex ratios varied between sites, were female-biased, and ranged from just over 50% to almost 90%. Histological examination of gonads revealed that at the sites with >60% females in the adult population, there was up to 38% occurrence of intersex gonads in fish identified through visual examination of the gonads as male. In the majority of intersex gonad cases, there was a large proportion (approx., 50%) of oocytes within the testicular tissue. In male dace, vitellogenin mRNA expression generally increased with distance downstream. We analyzed river water for 28 endocrine disrupting compounds from eight functional classes, most with confirmed estrogen-like activity, including synthetic estrogens and hormone therapy drugs characteristic of municipal wastewater effluent, plus natural hormones and veterinary pharmaceuticals characteristic of livestock production. The spatial correlation between detected chemical residues and effects to dace physiology indicate that multiple land uses have a cumulative impact on dace in the Oldman River and effects range from altered gene regulation to severely female-biased sex ratios.