Document Title:

Endocrine Disruption in Razorback Sucker and Common Carp on National Wildlife Refuges along the Lower Colorado River : Final Report

Carrie Marr


PUBLICATION DATE: September 2007

To provide the entire Lower Colorado River with the first endocrine disruption reconnaissance study on native and non-native fishes (razorback suckers and common carp), the U.S. Fish and Wildlife Service (FWS) chose three sampling locations, Lake Mohave, Havasu National Wildlife Refuge, and Cibola National Wildlife Refuge, below Lake Mead, in 2002, to collect steroid hormones, vitellogenin, thyronine, thryoxine, sperm viability, histology, and environmental contaminants concentrations in whole body tissue and sediments. Tissue concentrations of total p,p’-DDT homologs, total brominated diphenyl ethers (BDEs), total chlordanes, and total polychlorinated biphenyls (PCBs) were all relatively low (parts per billion (ppb) range). Total p,p’-DDT homologs were detected at the highest concentrations of any environmental contaminant in this study. There were significant differences between environmental contaminants and sites. For example, while total DDT-homologs were highest at Cibola and lowest at Havasu, total PCBs and total BDEs were greatest at Mohave and lowest at Cibola. Endocrine disruption in endangered razorback suckers was not found although data indicates slightly elevated concentrations of 17ß-estradiol in female razorback suckers. A few indications of endocrine disruption in carp were found. Male carp vitellogenin concentrations (0.18-0.38 mg/mL) were elevated compared to normal male vitellogenin concentrations around the country and previous Lake Mead studies (0.01-0.1 mg/mL). Other carp data, such as elevated 17ß-estradiol in females and lowered 11-ketotestosterone in females, may reflect exposure to a variety of environmental stressors or intrinsic differences between the Lower Colorado River (LCR) and other sites, but do not indicate endocrine disruption. Differences in biomarker results between LCR sampling sites were also apparent. In most cases, Mohave had significantly different hormone concentrations or condition indices than Havasu or Cibola. For example, razorback sucker E/T ratios were significantly higher in both males and females at Mohave than the other sites, although male E/T ratios never exceeded one, an indicator of endocrine disruption. Also, sperm viability in Mohave carp was significantly lower (78.5%) compared with Havasu carp (95%). Regressions between environmental contaminants and hormones or condition indices yielded significant results, but no consistent relationships were found. Thus, while environmental contaminants may be affecting the health of fish in the Lower Colorado River, clear cause-and-effect relationships could not be determined at this time. Other factors in the Lower Colorado River that may influence hormone concentrations or condition indices and should be taken into consideration include trophic dynamics of each sampling site, nutrient status of fishes, and other stressors besides environmental contaminants (season, photoperiod, and hydrology of each site). 2N47

U.S. Fish and Wildlife Service



U.S. Fish and Wildlife Service - Arizona Ecological Services Field Office

Last updated: June 12, 2015