Fish Hatchery Management - fisheries & aquaculture

BROODSTOCK, SPAWNING. AND EGG HANDLING 169hours at 34"F and to warm the stored milt to the ambient water temperaturebefore fertilization.Cryopreservation (freezing) of sperm from several warm- and coldwaterspecies 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 maintainedtheir fertility for l2 hours after being stripped, and a few were still fertileafter 175 hours. Sockeye milt maintained its fertility for I t hours and fertilizeda few eggs after l0l hours. Pink salmon eggs have maintained theirfertility for 8 hours, and some were still fertile at 129 hours. Milt of pinksalmon maintained its fertility for 33 hours after being stripped from themale, and fertilized 65'l| of the eggs after 57 hours; none were fertilizedafter U1 hours. Some fish culturists have obtained 90fi fertilization withpink 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'Fmaintained an 80'lu fertility when fertilized with fresh sperm. Chum salmonsperm stored under similar conditions for 36 hours maintained a 90% fertilitywhen applied to fresh eggs.Experiments with fall chinook salmon eggs and sperm have shown thatthe eggs are more sensitive to storage time and temperature than sperm.After 4tl hours storage at 33'F, egg mortality was approximately 470/0. Mortalitywas 100(li, after 48 hours storage at 56'F. Forty-eight-hour storage ofsperm at 56"F resulted in about a 129ir mortality. The stored eggs were fertilizedwith freshly collected sperm and the stored sperm was used to fertilizefreshly spawned eggs.AnestheticsAnesthetics relax fish and allow increased speed and handling ease duringthe spawning operation. In general, the concentration of the anestheticused must be determined on a trial and error basis with the particularspecies of fish being spawned, because such factors as temperature andchemical composition of the water are involved. Fish may react differentlyto the same anesthetic when exposed to it in a different water supply. Beforeany anesthetic is used, it is advisable to test it with several fish.At least 15 anesthetic agents have been used by fish culturists. Of theanesthetics reported, quinaldine (2-methylquinoline), tricaine methane sulfonate(MS-222), and, benzocaine are the most popular fish anestheticscurrently 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 forseveral seconds, attempting to remain in an upright position. As they lose