Teleost fishes exhibit a range of spawning modes that differ among the recruitment and timing of release of gametes. Oocyte staging is critical for understanding when females will spawn and in what spawning mode. Most of the data on reproductive biology of marine fishes is generated by fisheries biologists using specimens that are not archived in museum collections. We turned to these collections to investigate reproductive biology, including spawning mode and frequency, in the deep-sea hermaphrodite, the Shortnose Green Eye, Chlorophthalmus agassizi. Histological examination of specimens preserved over 50 years ago revealed both ovarian and testicular tissues in an ovotestis. Simultaneous activity of the female germinal epithelium and ongoing oocyte maturation and ovulation in these fishes which were preserved while spawning constitutes the basic mechanism of the asynchronous spawning mode in fishes: the germinal epithelium produces new follicles during or between spawning events. Well-preserved, archival museum specimens can provide information on reproductive biology for many taxa, especially rare species, which may never be the subject of detailed fisheries biology studies.