Validation of Gender Specific Markers in Plasma and Surface Mucus of Moronids and It's Utility for Broodstock Evaluation

Sex steroids and vitellogenin (VTG) are used routinely to investigate the reproductive systems of teleost fishes.  These markers are typically measured in plasma; however surface mucus samples have been shown to be an effective substitute in several species of fish.  We are attempting to validate mucus sampling as an approach to investigate reproductive events in white bass Morone chrysops and if mucus sampling can be used to monitor progression towards spawning in natural and compressed spawning cycles of fish.  In our validation study, reproductively mature white bass were collected during the March and April, 2010 spawning period via angling and electrofishing.  Male and female white bass were injected with carp pituitary extract (10 mg/kg) or saline, and plasma and mucus samples were collected and assayed for 11α-ketotestosterone (11-KT).  Samples from males and females treated with estradiol (10 mg E₂/kg) or the peanut oil carrier were also collected and assayed for VTG.  Simple linear regression analysis revealed a significant relationship (p=0.004) between 11-KT concentrations in the mucus and plasma.  Correlations of VTG between mucus and plasma samples are being determined.  Mucus of white bass broodstock was collected during artificial spawning events at the USDA HKD National Aquaculture Research Center in Stuttgart, Arkansas.  Samples were collected prior to hormone injection and ~24 h post injection.  Sperm and eggs were collected to determine sperm concentrations (sperm/ml; spermatocrit) and relative fecundity (eggs/kg of fish), respectively.  Mucus samples will be assayed and relationships between gender specific markers and reproductive output determined.  We will present comparisons of natural and compressed spawning events to illustrate the utility of mucus sampling as a tool to monitor the reproductive cycle and assist in broodstock selection of white bass.