142 FISH HATCHERY MANAGEMENT 



feet out from shore. As soon as fry become numerous, they can be captured 

 with a small fry seine and transferred to rearing ponds at the rate of 

 300,000 to 600,000 fry per acre. From this stocking rate, a harvest of about 

 150,000 fathead minnows can be expected. 



During the first few weeks of life following transfer to the rearing pond, 

 fry grow very rapidly. Within 4 to 8 weeks, many of these fish will mature 

 and begin to spawn. When this occurs, the pond may become overstocked 

 and the fish become stunted. The excess fry should be transferred to 

 another pond or destroyed. 



A productive pond should have a good plankton density; a Secchi disk 

 reading of about 12 inches should be maintained. Fathead minnows readily 

 accept a formulated diet, usually in the form of meal. The amount recom- 

 mended is 2% of body weight per day, not to exceed 25 pounds per day 

 per acre. In 6 to 10 weeks this procedure will produce 2-inch forage organ- 

 isms. 



GOLDFISH 



Goldfish are good forage fish. This is a hardy species that prospers during 

 hot weather. Goldfish feed largely on plankton, but will take insects and 

 very small fish. They reproduce in large numbers and grow rapidly. 



Goldfish normally start spawning when the water reaches 60°F and con- 

 tinue to spawn throughout the summer if the temperature remains above 

 60°F and the fish are not overcrowded. The favorite spawning time is right 

 after sunrise on sunny days. The females lay their eggs on grass, roots, 

 leaves, or similar objects. A female goldfish may lay 2,000 to 4,000 eggs at 

 one time and may spawn several times during the season. The eggs are 

 adhesive and stick to any object they touch. The live eggs are clear and 

 turn brown as they develop; dead eggs are cloudy and opaque. The eggs 

 hatch in 6 to 7 days at a water temperature of 60°F. 



Goldfish averaging 0.25 to 0.75 pound reproduce well and should be 

 used for broodstock. Broodstock overwintered in crowded ponds will not 

 spawn in the ponds. Maximum egg production is obtained by keeping the 

 broodfish in the overwintering pond until after the last spring frost. Then 

 the fish are stocked in the production ponds at the rate of 100-200 adults 

 per acre without danger of frost damaging the eggs or fry. Goldfish will ac- 

 cept formulated feeds and feeding rates should be set to produce 2-3-inch 

 fish in the shortest time. 



Broodstock ponds should be fertilized to insure that phytoplankton pro- 

 duction is sustained all summer. Secchi disk readings should be 18 inches 

 or less. 



Ponds should contain suitable natural vegetation or artificial spawning 

 material. The water level is commonly dropped in early spring to en- 

 courage the growth of grass along the shoreline. When the ponds are filled, 



