BROODSTOCK, SPAWNING, AND EGG HANDLING 165 



thousand. The vent must be covered to prevent egg loss. Fish will become 

 sufficiently relaxed for removal of eggs within 1 to 2 minutes. Workers 

 should wear gloves to prevent injury from opercular and fin spines. Strip- 

 ping follows the procedure previously described in this chapter. 



Because the broodfish of anadromous species of Pacific salmon die after 

 spawning, no advantage is obtained by stripping the female. Females are 

 killed and bled. Bleeding can be accomplished by either making an inci- 

 sion in the caudal peduncle or by cutting just below the isthmus and 

 between the opercula to sever the large artery leading from the heart to the 

 gills. The females are allowed to bleed for several minutes before being 

 spawned. A mechanical device is in common use that effectively kills and 

 bleeds the fish by making a deep cut through the body behind the head. 

 Bleeding reduces the chance of blood mixing with the eggs and reducing 

 fertilization. The point of the spawning knife is placed in the vent to 

 prevent the loss of eggs and the fish is lifted by the gill cavity and held 

 vertically over a bucket, such that the vent is 7-I inch above the lip of the 

 bucket. The fish can be held securely in this position by bracing the back 

 of the fish between the spawner's knees. An incision is made from the vent 

 to a point just below the ventral fin, around the ventral fin, back to the 

 center line, and upward to a point just beneath the gill cavity. If the fish is 

 ripe, most of the eggs will flow freely into the bucket (Figure 56). The 

 remaining ripe eggs can be dislodged by gently shaking the viscera. If the 

 fish is not ripe, gentle shaking will not dislodge the eggs and such females 

 should be discarded. Eggs that can only be dislodged by greater force will 

 be underdeveloped and infertile. 



The spawning knife needs a sharp blade, but should have a blunt tip to 

 avoid damage to the eggs during the incision. Linoleum knives have been 

 used for this purpose, but personal preference usually determines the 

 choice of the knife. 



Male salmon also are killed prior to spawning. Milt is hand stripped 

 directly onto the eggs in the bucket. The eggs and milt are gently mixed 

 by hand. 



In the case of Atlantic salmon or steelhead, which may return to spawn 

 more than once, females should not be killed to obtain eggs. A female fish 

 can be spawned mechanically by placing her into a double walled, rubber 

 sack with the tail and vent of the fish protruding. The sack can be adjust- 

 ed to fit each fish. Water entering between the walls of the sack causes a 

 pressure against the entire fish, and will express the eggs if they are ripe. 

 Female fish handled in this way seem to recover more rapidly than from 

 other methods of stripping. Milt is collected from the males and stored in 

 test tubes. A male fish is held upside down and the milt is gently pressed 

 out and drawn into a glass tube with suction. 



Reduction of damage to broodstock and increased efficiency are factors 

 of prime importance in any spawning operation. The use of air pressure 



