Sex steroids in plasma of lake whitefish Coregonus clupeaformis during spawning in Lake Erie

Lake whitefish, Coregonus clupeaformis, were collected from the Western basin of Lake Erie during spawning. Free and conjugated (sulfated and glucuronidated) steroids including testosterone (T), 11-ketotestosterone (11-kT), estradiol-17β (E2) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in the plasma by radioimmunoassay. In males, the progression of spermiation was characterized by a significant decrease in plasma free steroids, whereas the levels of conjugated steroids remained similar and low, except for sulfated and glucuronidated testosterone. Plasma sex steroids did not correlate with the density or the motility of the spermatozoa. In females, the concentration of plasma T was significantly higher in preovulating than in ovulating females. The levels of E2 and 17,20βP in ovulating lake whitefish exhibited large variations ranging from below detection limit to 0.9 ng ml^-1 and from 0.2 to 13 ng ml^-1, respectively. Analysis of conjugated steroids revealed high levels of glucuronidated and sulfated 17,20βP and glucuronidated T in females ovulating in December. However, no significant differences in the proportion of the conjugated steroids were observed.