Endocrine Disrupting Chemicals and Prevalence of Intersex in Fish Populations in New Jersey

Science Center Objects

NJ WSC and Leetown Science Center scientists in cooperation with the New Jersey Department of Environmental Protection were tasked with characterizing endocrine disruption in smallmouth bass from New Jersey.


Processing Fish at Echo Lake

Scientists conducting health assessment on smallmouth bass collected from Echo Lake, NJ.

(Credit: Robert Newby, NJ DEP. Public domain.)

Priority Questions:

  • Do biological manifestations of ED occur in smallmouth bass in NJ lakes and streams?

  • Is estrogenic activity, used as a screen for EDC's, present in NJ surface waters at concentrations sufficient to elicit a biological response?

Map of the Intersex Fish Sampling sites

MAp of the Intersex Fish sampling sites in New Jersey

(Public domain.)


A sampling network of over 100 sites (lakes and streams) was established based on existing monitoring networks and geospatial information. Surface water was collected under low flow conditions at 16 reservoirs and 85 river locations and analyzed for estrogenicity (hormone assay used as an indicator of estrogenic compounds).

Estrogenicity in water collected under low flow conditions in combination with land-use gradients and fish population information was used to select the nine priority sites for fish health assessments.  At each fish location surface water was collected and analyzed for estrogenicity in the spring during fish sampling and again the following fall under low flow conditions.  

Scientists collecting smallmouth bass

NJ Department of Environmental Protection scientists collecting smallmouth bass from the Delaware River near Lambertville, NJ.

(Credit: Robert Newby, NJ Department of Environmental Protection. Public domain.)

Smallmouth bass (10 per sex) were sampled pre-spawn (spring) from 7 reservoirs and 2 river locations.

  • External health assessment

  • Length/width, sex and age data collected

  • All internal organs preserved for histopathology

  • Assessment of males for intersex

  • Blood collected for plasma vitellogenin measurement (egg yolk precursor protein, another line of evidence related to intersex conditions).


Information gained from this study will help state cooperators better understand the occurrence and potential effects of EDCs in surface water and determine feasible management steps necessary to help ameliorate the effects.






USGS NJWSC Team: Anna Boetsma, Brianna Williams, Kristin Romanok




    Division of Science, Research and Environmental Health

    Bureau of Freshwater and Biological Monitoring

   Division of Fish and Wildlife Bureau of Freshwater Fisheries  

USGS Environmental Health