The effects of endocrine disruptors on the reproductive biology of resident fish in the Sacramento-San Joaquin Delta have been studied at BML. Endocrine disruption in the inland silverside (Menidia spp.) has been the focus for a number or years since populations of native fish are so low and several are listed as endangered, Menidia is an ideal indicator species as they have a limited home range, are found across broad salinity gradients, and are reproductive for about 4-6 months.