Field Collection, Handling, and Storage of Sperm of the Endangered Razorback Sucker

Abstract

We developed methods for the collection, handling, and refrigerated storage of sperm from the endangered razorback sucker Xyrauchen texanus. Sperm samples were obtained from 56 of 78 male razorback suckers collected from Lake Mohave (Colorado River) during the 1994 and 1995 spawning seasons. There were significant differences among the osmolalities of blood plasma, ovarian fluid, and seminal plasma. Maximum sperm motility was observed 3 s after dilution with river water and was maintained for 16 ± 8 s (mean ± SD). Motility ceased 70 ± 32 s after the addition of water. Given the short time that sperm were motile, care should be taken to ensure complete and early mixing of gametes during artificial spawning of razorback suckers. Refrigerated sperm (4°C) retained more than 90% motility when stored at 290 milliosmols/kg in calcium-free Hanks' balanced salt solution (C-F HBSS). Sperm diluted 1:1 with C-F HBSS had significantly higher motility compared with motility of undiluted sperm at the end of 24 h. Motility of sperm diluted with three proportions of C-F HBSS decreased at similar rates during 8 d of storage. Gamete collection and storage offers potential for enhancing management efforts for razorback suckers by allowing increased control of artificial spawning. In this regard, sperm may be collected by sampling crews and stored for days at the hatchery for production of fry.