BROODSTOCK, SPAWNING, AND EGG HANDLING 



157 



Figure 49. Equipment used for spawning wild coolwater fishes (trap net shown 

 in background). The males and females are held separately in holding tanks con- 

 taining an anesthetic (A, B). A bench with a spawning pan (C) is provided for 

 the spawn taker. (FWS photo.) 



The fish is then held with the belly downward over a pan, and the eggs are 

 forced out gently by a massaging movement beginning forward of the vent 

 and working back toward it. Care should be taken to avoid putting pres- 

 sure too far forward on the body as there is danger of damaging the heart 

 or other organs (Figure 50). After the eggs have been extruded, a small 

 amount of milt (sperm) is added from a male fish. Milt is expressed from a 

 ripe male in much the same manner as the eggs are taken from a female 

 (Figure 5l). If either eggs or milt do not flow freely, the fish is not suffi- 

 ciently ripe and should not be used. The fish should be examined frequent- 

 ly, as often as twice a week, to determine ripeness. Fish rarely spawn of 

 their own accord under hatchery conditions, and, if they are not examined 

 for ripeness frequently, overripe eggs will result. Muskellunge, however, 

 will often spawn on their own accord. 



The two generally accepted procedures for handling eggs during fertili- 

 zation are often referred to as the wet and dry methods. In the dry method 

 of fertilization, water is not introduced before the eggs are expressed into 

 the pan, and all equipment is kept as dry as possible. Sperm and eggs are 

 thoroughly mixed and usually left undisturbed for 5 to 15 minutes before 



