140 FISH HATCHERY MANAGEMENT 



Forage Fish 



Forage species cultured as feed for predatory broodfish vary depending on 

 the species of broodfish being maintained. Several factors must be con- 

 sidered when a forage organism is selected. The forage must not be too 

 large for the predator to consume nor too small to provide adequate nour- 

 ishment, and should be able to reproduce in adequate numbers at the time 

 v^hen it is needed. Forage species should have the right shape and 

 behavior to attract the predator, be easily captured by the broodfish, and 

 require little pond space to rear. If the forage can be obtained commercial- 

 ly at a reasonable cost, production space and time will be saved at the 

 hatchery. 



Species of forage fish propagated as food include suckers, fathead min- 

 nows, goldfish, golden shiners and Tilapia. Shad, herring, bluegills, and 

 trout are used to a lesser degree as forage fish. Suckers, fathead minnows, 

 and goldfish usually are used with coolwater broodfish. These species are 

 early spawners, making them available as forage when needed by the 

 broodfish. Northern pike, walleye, and muskellunge prefer a long slender 

 fish with good body weight, such as the sucker. 



Culture of forage fish varies with the species; some notes about the most 

 frequently utilized species follow. 



WHITE SUCKER 



White suckers occur east of the Great Plains from northern Canada to the 

 southern Appalachian and Ozark mountains. They prefer clearwater lakes 

 and streams. In early spring, they run upstream to spawn in swift water 

 and gravel bottoms, although they also will spawn to some extent in lakes 

 if there are no outlets and inlets. White suckers have diversified feeding 

 habits, but prefer planktonic crustaceans and insect larvae. 



Broodfish usually are taken from streams during the natural spawning 

 run. These fish are hand-stripped and the eggs are hatched in jars. After 

 hatching, the fry are stocked in ponds prepared for the production of zoo- 

 plankton. Stocking rates vary with the size of the desired forage: 

 40,000-60,000 per acre for 1-2-inch fish; 20,000-40,000 for 2-4-inch fish; 

 5,000-20,000 for 4-6- inch fish. 



Ponds of moderate fertility usually produce the most suckers. Sterile 

 ponds do not produce enough food for white suckers and excessively fertile 

 ponds often produce too much aquatic vegetation. Ponds with large popu- 

 lations of chironomid fly larvae (bloodworms) in the bottom muds will 

 produce good sucker crops year after year. Loam and sandy- loam soils pro- 

 duce the best chironomid populations; peat and peat-loam ponds are ade- 

 quate for this purpose, but silt and clay- loam ponds are poor. Ponds with 



