Fresh storage of rainbow trout ( Oncorhynchus mykiss) semen using a non-aqueous medium

Several media for the storage of semen from rainbow trout ( Oncorhynchus mykiss) at 4°C were evaluated. Treatments included semen diluted 1:1 with fluorocarbon, semen diluted 1:1 with a 1:1 fluorocarbon: extender emulsion, semen diluted 1:1 with a 2:1 fluorocarbon: extender emulsion, semen diluted 1:1 with extender, or semen stored undiluted. The treatments were stored either under a moisture-saturated air atmosphere or non-saturated air atmosphere. Efficacy of treatment was evaluated using motility rating, per cent dead sperm as determined by fluorometry, LDH leakage in seminal plasma, and fertility trials during the storage period. Unlike motility ratings and fluorometry, measurement of LDH leakage to estimate sperm viability during storage with fluorocarbon compounds did not give clear results due to the separation of the non-aqueous fluorocarbon from the aqueous seminal plasma phase. Semen diluted 1:1 with fluorocarbon maintained sperm viability at an acceptable level for 37 days. The moisture-saturated air atmosphere gave significantly greater duration of sperm viability than the non-saturated atmosphere. The use of fluorocarbon compounds for storage of salmonid semen shows promise for maintaining sperm viability for several weeks. Use of simple equipment will make this method readily adaptable to hatcheries.