Validation of Nonlethal Sex Determination for Black Crappies during Spring

Abstract

I evaluated the accuracy of using differences in body coloration, gamete stripping, and abdominal distension in females as a nonlethal method for determining the sex of black crappies Pomoxis nigromaculatus collected from two Minnesota lakes during spring (late April–early June). Sex assignments based on these three attributes were 93% accurate for all black crappies (211 of 227) and 98% accurate (174 of 177) for black crappies of 200 mm or more total length. The difference in body coloration between sexes was the most useful trait for identifying sex, but the distended abdomen of females and gamete stripping aided in identifying sex in some instances. Nonlethal sex assignment was less reliable for black crappies less than 200 mm (74% accurate; 37 of 50), largely because of the lack of dark coloration in males. The sex of black crappies of 200 mm or more can be identified accurately without killing the fish, but that of smaller crappies should be determined by means of visual inspection of the gonads.