Fish Hatchery Management - fisheries & aquaculture

140 FISH HATCHERY MANAGEMENTForage FishForage species cultured as feed for predatory broodfish vary depending onthe species of broodfish being maintained. Several factors must be consideredwhen a forage organism is selected. The forage must not be toolarge for the predator to consume nor too small to provide adequate nourishment,and should be able to reproduce in adequate numbers at the timewhen it is needed. Forage species should have the right shape andbehavior to attract the predator, be easily captured by the broodfish, andrequire little pond space to rear. If the forage can be obtained commerciallyat a reasonable cost, production space and time will be saved at thehatchery.Species of forage fish propagated as food include suckers, fathead minnows,goldfish, golden shiners and Tilapia. Shad, herring, bluegills, andtrout are used to a lesser degree as forage fish. Suckers, fathead minnows,and goldfish usually are used with coolwater broodfish. These species areearly spawners, making them available as forage when needed by thebroodfish. Northern pike, walleye, and muskellunge prefer a long slenderfish with good body weight, such as the sucker.Culture of forage fish varies with the species; some notes about the mostfrequently utilized species follow.WHITE SUCKERWhite suckers occur east of the Great Plains from northern Canada to thesouthern Appalachian and Ozark mountains. They prefer clearwater lakesand streams. In early spring, they run upstream to sPawn in swift waterand gravel bottoms, although they also will spawn to some extent in lakesif there are no outlets and inlets. White suckers have diversified feedinghabits, but prefer planktonic crustaceans and insect larvae.Broodfish usually are taken from streams during the natural spawningrun.These fish are hand-stripped and the eggs are hatched in jars. Afterhatching, the fry are stocked in ponds prepared for the production of zooplankton.Stocking rates vary with the size of the desired forage:40,000-60,000 per acre for l-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. Sterileponds do not produce enough food for white suckers and excessively fertileponds often produce too much aquatic vegetation. Ponds with large populationsof chironomid fly larvae (bloodwor-.) i.t the bottom muds willproduce good sucker crops year after year. Loam and sandy-loam soils producethe best chironomid populations; peat and peat-loam ponds are adequatefor this purpose, but silt and clay-loam ponds are poor. Ponds with