138 FISH HATCHERY MANAGEMENT 



Channel catfish broodstock usually are maintained in a holding pond 

 and fed a good quality formulated diet. The density of broodfish should 

 not exceed 600-800 pounds per acre. The amount of food provided 

 depends on water temperature; above 70°F feed 3-4% of body weight per 

 day; from 50°-70°F, 2% per day; below 50°, 2% twice per week. Spawning 

 success and the quality of eggs and fry are improved, in many cases, if the 

 fish are provided a diet including natural food. For this reason, many cul- 

 turists supplement a formulated diet with cultured forage fish. Another 

 practice is to supplement a diet once or twice a week with liver fed at a 

 rate of 4% of fish weight. 



Differentation between male and female channel catfish also can be a 

 problem. The secondary sex characters are the external genitalia. The fe- 

 male has three ventral openings — the anus, the genital pore, and the uri- 

 nary pore — whereas the male has only an anus and urogenital pore. In the 

 male, the urogenital pore is on a papilla, while in the female the genital 

 and urinary openings are in a slit, without a papilla. Experienced breeders 

 can discern the sex of large broodfish and detect the papilla by rubbing in 

 a posterior to anterior direction or by probing the urogenital opening with 

 an instrument such as a pencil tip. 



Tertiary sex characteristics develop with approaching sexual maturation. 

 In the male, they include a broad muscular head wider than the body, a 

 darkening of the body color, and a pronounced grayish color under the 

 jaws. Females have smaller heads, are lighter in color, and have distended 

 abdomens at spawning time. 



Brood bluegills generally are obtained by grading or selecting larger 

 fingerlings from the previous year's crop. These replacements may either be 

 mixed with adults stocked in spawning- rearing ponds or stocked alone in 

 production ponds. The preferred procedure is to keep year classes of 

 broodfish separate so that systematic replacement can be carried out after 

 the broodfish have been used for three spawning seasons. Distinctive sexu- 

 al characteristics differentiate male bluegills from females (Figure 44). 



Special holding ponds normally are established for keeping broodfish. If 

 the stocking density is below 200 pounds per acre, the broodstock can be 

 sustained by natural food organisms, provided the pond has had a good fer- 

 tilization program. If more than 200 pounds per acre are held, a supple- 

 mental formulated diet usually is fed. The feeding rate is "iX of body 

 weight at water temperatures above 70°F, and 2.5% of body weight at tem- 

 peratures from 70-50°F. Below 50°F, feeding can be suspended entirely. 



Redear sunfish do not adapt to formulated feed as readily as bluegills be- 

 cause they are more predatory. Diets can be fed at 0.5—2%) of body weight, 

 depending on temperature, but suitably sized organisms also should be pro- 

 vided. Redear sunfish eat shelled animals and a holding pond should sup- 

 port a good crop of mollusks. 



