Effect of capture, confinement and repeated sampling on plasma steroid concentrations and oocyte size in female striped trumpeter Latris lineata (Latrididae)

Abstract

Wild female striped trumpeter were caught during the spawning season to examine the effect of capture, confinement and repeated handling on reproductive function. Blood and ovarian samples were obtained from 5 females within 10 minutes of capture and from a pool of female fish (n = 17), including the original 5, that were sampled regularly from Day 2 to Day 13 after capture. Plasma concentrations of cortisol, testosterone (T), 17β-oestradiol (E₂) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured by radioimmunoassay. Four of the 17 fish ovulated and a small volume of eggs was obtained by hand stripping. Mean oocyte size did not change significantly, although there was a general trend toward decreasing oocyte diameters over time. Plasma concentrations of T and E₂ decreased significantly after capture, and remained low thereafter. Concentrations of 17,20βP remained unchanged apart from a decrease on Day 13. Cortisol concentrations significantly increased after capture and remained elevated until Day 5, with subsequent elevations on Days 7 and 9. These results suggest that the stress of capture, confinement and repeated handling inhibits the ovarian production of T and E₂ but not 17,20βP and arrests oocyte development at all but the most advanced stages.