Nonlethal Tools to Identify Mass Ovarian Follicular Atresia in Burbot

Abstract Skipped spawning, or variation in spawning periodicity, occurs many annual fish species and is an important consideration for population management. We assessed plasma sex steroid concentrations measured gonad size ovarian follicle diameter as metrics to nonlethally identify mass follicular atresia, which may contribute skipped Burbot Lota lota. maintained wild captivity exposed them increasing water temperatures during a 3-wk period before the season induce atresia. collected follicles, blood plasma, gonadal sonograms from weekly between January 28, 2018, March 25, 2018. histologically analyzed follicles confirm stage of maturity. steroids testosterone (T) estradiol-17β (E2) by radioimmunoassay. circumference ultrasonography image analysis. Mean T concentration decreased 8.94 ng/mL late vitellogenesis 1.83 suggesting that be used do not recommend using E2 atresia because rapidly completion initiation Burbot; therefore, accurately 4.05 cm 3.65 final week study, advanced The nonlethal tools assessed—plasma concentrations, ultrasonography, diameter—enable fisheries biologists determine occurrence frequency among Lake Roosevelt applied other populations.