Assigning Sex and Reproductive Stage to Adult Lake Sturgeon using Ultrasonography and Common Morphological Measurements

Abstract

Sex determination of fish species is difficult to assess when sexual dimorphism and gametes are not apparent. For threatened and endangered fish species, noninvasive techniques are needed when determining sex to minimize stress and the potential for mortality. We evaluated the use of a portable ultrasound unit to determine sex of Lake Sturgeon Acipenser fulvescens in the field. Ultrasound images were collected from 9 yellow-egg (F2, F3), 32 black-egg (F4, F5), and 107 fully developed male (M2) Lake Sturgeon. Two readers accurately assigned sex to 88–96% of fish, but accuracy varied in relation to maturity stage. Black-egg females and fully developed males were correctly identified for 89–100% of the fish sampled, while these two readers identified yellow-egg females only 33% and 67% of the time. Time spent collecting images ranged between 2 and 3 min once the user was comfortable with operating procedures. Discriminant analysis revealed the total length : girth ratio was a strong predictor of sex and maturity, correctly classifying 81% of black-egg females and 97% of the fully developed males. However, yellow-egg females were incorrectly classified on all occasions. This study shows the utility of using ultrasonography and a total length : girth ratio for sex determination of Lake Sturgeon in later reproductive stages around the spawning season.

Received April 7, 2015; accepted September 29, 2015

ACKNOWLEDGMENTS

The authors thank staff of the Lake St. Clair Fisheries Research Station: Mike Thomas, Todd Wills, Roy Beasley, Brad Utrup, Jeremy Maranowski, and Jason Pauken. We also thank staff from the U.S. Coast Guard Station in Port Huron, Michigan, for use of their facilities during the duration of this project. Trevor Pitcher and Jennifer Smith from the University of Windsor; Lloyd Mohr, Rich Drouin, Chris Gignac, Robert Dietz, Christine Scott, Karen Soper, and Tyler Genereaux from the Ontario Ministry of Natural Resources; Lisa Kaulfersch, Steven Gray, and Timothy Desorcie from the U.S. Geological Survey Great Lakes Science Center; Margaret Hutton, Eric Stadig, and Jeremy Moore from the U.S. Fish and Wildlife Service; Tina Whitaker and Jami Marranca from West Virginia University; and volunteers Sheri Faust, Mitchell Dender, and Audrey Elzerman. This article is contribution number 1960 of the U.S. Geological Survey Great Lakes Science Center. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service or the U.S. Geological Survey. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Partial funding from this research came from the Great Lakes Restoration Initiative and Great Lakes Fishery Trust (grant number2011.1200).