M4 PM Endocrine Disruption in Fish (Part 2)
Monday, 14 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(BLA-1117-818764) Intersex in Fish: Species and Site Comparisons.

Blazer, V¹, Hinck, J², Schmitt, C², ¹ USGS, National Fish Health Research Laboratory, Leetown Science Center, Kearneysville, WV, 25430² USGS, Columbia Environmental Research Center, Columbia, MO

ABSTRACT- Intersex or ovotestis is a gonadal change that has been used as an indicator of exposure to reproductive endocrine disruptors in gonochorist fishes. This change is most often detected microscopically in male gonads and is characterized by the presence of oocytes. Although a wide variety of natural and manufactured chemicals are know to possess estrogenic activity in fishes, a high prevalence of intersex has most commonly been associated with domesticate sewage treatment discharges or runoff from agricultural/confined animal feeding operations. As part of the U.S. Geological Survey′s Biomonitoring of Environmental Status and Trends (BEST) program, gonads from 1400 common carp and 773 bass (primarily largemouth bass, but including smallmouth and spotted) have been collected from sites in the Mississippi, Rio Grande, Columbia and Colorado river drainages and examined microscopically. Using the complete data set we examined species differences and identify sites at which intersex was observed. The target sample size was 10 fish of each sex for each species per site. However, this is not always obtained. Hence, we compared prevalence of intersex only at those sites at which six or more male fish of a particular species were collected. In addition, using gonads collected from smallmouth and largemouth bass in the Potomac drainage we assessed the current BEST protocols for tissue collection: cut 1-cm pieces from the posterior end (bottom tips) of the gonads and place a maximum of five in fixative, and statistically evaluated the probablility of finding intersex when present depending on number and size of pieces examined.

Key words: intersex, endocrine disruption, carp, bass