Extending storage time for Rainbow Trout (Oncorhynchus mykiss) milt: the effect of temperature

Howell, Alex Elizabeth
Fish hatcheries collect and store milt (sperm) as part of their standard breeding protocol, and longer-term storage is desirable for various reasons such as poor performance in males or spawning issues when the timing of egg production by females is mismatched with the timing of milt production. A previous study in 2016 found that rainbow trout (Oncorhynchus mykiss) milt can be stored and remain viable for up to seven days. However, we still don't know if rainbow trout milt can be stored for longer periods of time or how temperature might affect storage time. The purpose of this current study is to: (1) observe how many days stored rainbow trout milt will remain viable based on motility and fertilization rate, and (2) investigate the effect of temperature on milt storage. I hypothesize that trout milt stored at 1.7˚C will remain viable longer and have a higher fertilization rate than milt stored at 4.2˚C. In addition, I hypothesize that despite motility, milt stored for longer periods (> 15 days) can still fertilize eggs. Individual milt samples from 15 male trout will each be divided into two groups and stored at the two temperatures for a paired design. During the course of the 21-day experiment, motility will be checked every 5 days and fertilization rate will be assessed on days 10 and 21. This study will assist the Story Fish Hatchery captive-breeding program by enhancing their understanding of longer-term storage potential for rainbow trout milt.
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