BROODSTOCK, SPAWNING, AND EGG HANDLING 169 



hours at 34°F and to warm the stored milt to the ambient water tempera- 

 ture before fertilization. 



Cryopreservation (freezing) of sperm from several warm- and coldwater 

 species has been successful for varying length of times and rates of fertility. 

 These procedures generally require liquid nitrogen and extending agents, 

 and are reviewed by Horton and Ott (1976). 



At 46° to 48°F, sockeye salmon eggs with no water added maintained 

 their fertility for 12 hours after being stripped, and a few were still fertile 

 after 175 hours. Sockeye milt maintained its fertility for 11 hours and fertil- 

 ized a few eggs after 101 hours. Pink salmon eggs have maintained their 

 fertility for 8 hours, and some were still fertile at 129 hours. Milt of pink 

 salmon maintained its fertility for 33 hours after being stripped from the 

 male, and fertilized 65"i of the eggs after 57 hours; none were fertilized 

 after 81 hours. Some fish culturists have obtained 90"(i fertilization with 

 pink salmon eggs and sperm stored for periods up to 20 hours at 43°F. 

 Storage of chum salmon eggs for 108 hours at temperatures of 36° to 42°F 

 maintained an 80"() fertility when fertilized with fresh sperm. Chum salmon 

 sperm stored under similar conditions for 36 hours maintained a 90% fertil- 

 ity when applied to fresh eggs. 



Experiments with fall chinook salmon eggs and sperm have shown that 

 the eggs are more sensitive to storage time and temperature than sperm. 

 After 48 hours storage at 33°F, egg mortality was approximately 47%. Mor- 

 tality was 100"o after 48 hours storage at 56°F. Forty-eight-hour storage of 

 sperm at 56°F resulted in about a 12"n mortality. The stored eggs were fer- 

 tilized with freshly collected sperm and the stored sperm was used to fertil- 

 ize freshly spawned eggs. 



Anesthetics 



Anesthetics relax fish and allow increased speed and handling ease during 

 the spawning operation. In general, the concentration of the anesthetic 

 used must be determined on a trial and error basis with the particular 

 species of fish being spawned, because such factors as temperature and 

 chemical composition of the water are involved. Fish may react differently 

 to the same anesthetic when exposed to it in a different water supply. Be- 

 fore any anesthetic is used, it is advisable to test it with several fish. 



At least 15 anesthetic agents have been used by fish culturists. Of the 

 anesthetics reported, quinaldine (2-methylquinoline), tricaine methane sul- 

 fonate (MS-222), and benzocaine are the most popular fish anesthetics 

 currently in use. Only MS-222 has been properly registered for such use. 



There are various stages of anesthesia in fish (See Chapter 6, Table 39). 

 When placed in the anesthetic solution, the fish often swim about for 

 several seconds, attempting to remain in an upright position. As they lose 



