Investigating the Utility of Measuring 11α‐Ketotestosterone and Vitellogenin in Surface Mucus as an Alternative to Plasma Samples in Assessments of the Reproductive Axis of White Bass

Abstract

AbstractSex steroids and vitellogenin measured in plasma have been used in a variety of fish species to investigate the reproductive system. Surface mucus has been shown to be an effective substitute for plasma in several species of fish. The goal of this study was to investigate the utility of mucus sampling as an approach to investigating the hypothalamic–pituitary–gonadal (HPG) axis in White Bass Morone chrysops. We measured 11α‐ketotestosterone and vitellogenin in both surface mucus and plasma samples from White Bass collected from a wild population during their annual spawning migration. Mucus and plasma samples were collected from male and female White Bass that were treated to stimulate the HPG axis (carp pituitary extract, 10 mg/kg; estradiol, 10 mg/kg) or treated with saline injections. Mucus and plasma concentrations of both vitellogenin and 11α‐ketotestosterone were positively correlated with one another. Treatments with estradiol led to higher amounts of vitellogenin in both plasma and mucus in both male and female fish. Assessments of 11α‐ketotestosterone in mucus correctly identified the sex of 90% of spawning White Bass, as did vitellogenin in 94%. These data demonstrate the potential utility of mucus sampling as a tool to less invasively assess the annual reproductive cycle, identify stimulation of the HPG axis, and identify fish sex in hatchery populations of White Bass.