Hormones from livestock operations may skew fish gender toward males

Read the full story at Great Lakes Echo.

Baby fish exposed to hormone-laden manure from Indiana farms were much more likely to be male than those raised in uncontaminated water, according to new research.

The findings add to evidence that farm runoff may alter fish hormones and affect their reproduction and development.

Full research article: Jessica K. Leet, Linda S. Lee, Heather E. Gall, Reuben R. Goforth, Stephen Sassman, Denise A. Gordon, James M. Lazorchak, Mark E. Smith, Chad T. Javfert, and Maria S. Sepúlveda (2012). “Assessing Impacts of Land-Applied Manure from Concentrated Animal Feeding Operations on Fish Populations and Communities.” Environmental Science & Technology 46(24), 13440-13447. DOI: 10.1021/es302599t.

Abstract: Concentrated animal feeding operation (CAFO) manure is a cost-effective fertilizer. In the Midwest, networks of subsurface tile-drains expedite transport of animal hormones and nutrients from land-applied CAFO manure to adjacent waterways. The objective of this study was to evaluate impacts of land-applied CAFO manure on fish populations and communities. Water chemistry including hormone, pesticide, and nutrient concentrations was characterized from study sites along with fish assemblage structure, growth, and endocrine disruption assessed in selected fish species. Although most CAFO water samples had hormone concentrations <1 ng/L, equivalent concentrations for 17β-E2 and 17α-TB peaked at >30 ng/L each during the period of spawning, hatching, and development for resident fishes. CAFO sites had lower fish species richness, and fishes exhibited faster somatic growth and lower reproductive condition compared to individuals from the reference site. Fathead minnows (Pimephales promelas) exposed to CAFO ditchwater during early developmental stages exhibited significantly skewed sex ratios toward males. Maximum observed hormone concentrations were well above the lowest observable effect concentrations for these hormones; however, complexities at the field scale make it difficult to directly relate hormone concentration and impacts on fish. Complicating factors include the consistent presence of pesticides and nutrients, and the difference in temperature and stream architecture of the CAFO-impacted ditches compared to the reference site (e.g., channelization, bottom substrate, shallow pools, and riparian cover).

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