Cold storage of the sperm of the endemic trout Oncorhynchus mykiss nelsoni: a strategy for short-term germplasm conservation of endemic species

Aiming to determine an appropriate protocol for short-term storage of the sperm of San Pedro Martir trout, Oncorhynchus mykiss nelsoni, wild fish previously matured in captivity were anesthetized and the semen, obtained by abdominal pressure, was suspended in Erdhal and Graham extender at 1:3, 1:6 and 1:9 dilution ratios and kept at 4 degrees C for 9 days with an undiluted sample as control. The percentages of sperm motility and membrane integrity were assessed daily. The results indicated that sperm suspended at a dilution of 1:9 can be stored at 4 degrees C with >= 80% motility and >= 65% membrane integrity for 7 and 6 days respectively. In addition, the results show that membrane integrity decreased more rapidly than motility, which suggests that it may be used as an early indicator of sperm damage during short-term cold storage. The results obtained are important to support future conservation programs of this trout.