What is normal? A characterization of the values and variability in reproductive endpoints of the fathead minnow, Pimephales promelas.

Jensen et al. [Jensen, K.M., Korte, J.J., Kahl, M.D., Pasha, M.S., Ankley, G.T., 2001. Aspects of basic reproductive biology and endocrinology in the fathead minnow (Pimephales promelas). Comp. Biochem. Physiol. C 128, 127-141.] investigated aspects of the normal reproductive biology of the fathead minnow (FHM, P. promelas), and subsequent studies have generated a large amount of additional reproductive data for endpoints such as plasma steroid hormone and vitellogenin concentrations, spawn interval, and secondary sex characteristics (i.e., nuptial tubercle score and fat pad weight). These data were analyzed and fitted with statistical distributions to improve understanding of the variability in normal, unexposed, adult male (n=154) and female (n=186) FHM. Summary statistics for most endpoints were consistent with results from other more limited studies of FHMs. Male fat pad weight, and in both sexes gonad and liver weights were found to be proportional to body weight. Multiple statistical distributions were found to characterize each endpoint with the exception of spawn interval. Based on one of the largest datasets ever compiled for controlled studies, results presented herein provide a robust point of reference for the quantitative assessment of reproductive processes in the fathead minnow.