154 



FISH HATCHERY MANAGEMENT 



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Figure 47. Spawning receptacles for channel catfish are placed in the pond 

 before it is filled with water. 



requires close inspection of nests with an underwater viewer. The method 

 allows the fish culturist to collect eggs, if so desired, for subsequent hatch- 

 ing under controlled conditions. It has the added advantage of allowing the 

 culturist to respawn broodfish during the height of the season. 



Culture of bluegills and other sunfishes is relatively simple. The 

 spawning-rearing pond method almost always is used for culturing these 

 species, although a few hatcheries transfer fry to rearing ponds. Best 

 spawning success with bluegills is obtained by using mature broodfish 

 weighing 0.3 to 0.6 pound. However, good production has been obtained 

 with 1-year-old fish averaging 0.10—0.15 pound at spawning time. When 

 broodstock of this latter size is used, an increased number of fish per acre 

 is needed to adequately stock the pond. Use of yearling broodstock gen- 

 erally results in less uniform spawning, which tends to cause greater size 

 variation in the fingerlings produced. Bluegills spawn when water tempera- 

 tures approach 80°F and several spawns can be anticipated during the sum- 

 mer. 



Catfish generally are spawned by either the open- pond or pen method. 

 In the open-pond method, spawning containers such as milk cans, nail 

 kegs, or earthenware crocks, are placed in the pond with the open end to- 

 ward the center of the pond (Figure 47). It is not necessary to provide a 

 spawning receptacle for each pair of fish, because not all fish will spawn at 

 the same time. Most culturists provide two or three receptacles for each 

 four pairs of fish. Fish will spawn in containers placed in water as shallow 

 as 6 inches and as deep as 5 feet. The receptacles are checked most easily 

 if they are in water no deeper than arm's length. 



Frequency of examination of spawning containers depends on the 



