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FISH HATCHERY MANAGEMENT 



systems, as introduced by Australian workers and used on some trout 

 species in this country, have made spawning fast, easy, and efficient (Fig- 

 ure 57). Two to four pounds of air pressure injected into the body cavity 

 by means of a hollow needle will expel the eggs. The needle is inserted in 

 the area between the pectoral and ventral fins midway between the mid- 

 ventral line and the lateral line. The possibility of damage to the kidney by 

 needle puncture is reduced if the posterior section of this area is used. The 

 needle should be sterilized in alcohol for each operation to reduce the pos- 

 sibility of infection. It is imperative that a female be ripe if the eggs are to 

 flow freely. When a fish is held in the normal spawning position, a few 

 eggs should flow from the fish without pressure on the abdomen. 



It is important that the fish be relaxed before the air pressure method is 

 attempted. An anesthetic should be used. The fish should be rinsed and 

 wiped fairly dry to prevent anesthetic dripping into the egg- spawning pan. 



Air should be removed from the body cavity before the fish is returned 

 to the water. This is best done by installing a two-way valve and a suction 

 line to the needle. A supplemental line may be used to draw off the air by 

 mouth, or the air may be forced out by hand when a check is made for 

 remaining eggs, although these methods are generally not as effective. 



Figure 56. Spawning Pacific salmon. Left, female is opened with a spawning 

 knife (cutting edge indicated by arrow). Right, milt is hand-stripped from a male 

 directly onto the eggs. 



