Production of Monosex Female Populations of Walleye from Intersex Broodstock

Abstract Monosex female populations of walleye Stizostedion vitreum were produced by fertilizing eggs with sperm obtained from intersex genetic female broodstock. To produce these broodstock, groups of walleyes at mean sizes of 50, 70, and 90 mm total length (TL) were fed a diet containing 17α-methyltestosterone at 15 mg/kg of food for 60 consecutive days. At age 2, three masculinized females from the 50-mm TL group were identified by the presence of both ovarian and testicular tissue. Mature spermatozoa were collected from these fish and used to fertilize eggs collected from normal females. Approximately 200 of the resultant progeny were reared to 145 mm TL. Morphological and histological examination of the gonads from a subsample of 35 of these fish confirmed that all were normal females. The potential uses of monosex female populations of walleye and the advantages of this indirect hormonal method of producing monosex female populations are discussed.