Fish Hatchery Management - fisheries & aquaculture

BROODSTOCK, SPAWNING, AND EGG HANDLING 155number of broodfish in the pond and the rate at which spawning is progressing.In checking a container, the culturist gently raises it to the surface.If this is done quietly and carefully, the male usually is not disturbed. Cautionshould be used, because an attacking male can bite severely. If the wateris not clear, the container can be slowly tilted and partly emptied.Catfish eggs may be handled in different ways. The eggs may be removed,or left in the spawning pond to hatch and the fry reared in theponds. Removal of the eggs has several advantages. It minimizes thespread of diseases and parasites from adults to youngr and provides for eggdisinfection. The eggs are protected from predation and the fry can bestocked in the rearing ponds at known rates.The pen method of spawning catfish utilizes pens about 10 feet long and5 feet wide located in a row in the spawning ponds (Figure 48). They areconstructed of wood, wire fencing, or concrete blocks. They should be enclosedon all four sides but the bank of the pond may be used as one side.The sides should be embedded in the pond bottom and extend at least 12inches above the water surface to Prevent fish from escaping. Water shouldbe 2-3 feet deep.Location of the spawning container in the pen is not critical, but generallyit faces away from the pond bank. Broodfish are sexed and paired inthe pens. Usually the best results occur when the male is equal in size to,or slightly larger than, the female. This discourages the female from eatingthe eggs that are being guarded by the male. After spawning, eggs andparent fish may be removed and another pair placed in the pen. Sometimes,the female is removed as soon as an egg mass is found, and the maleis then allowed to hatch the eggs. Usually, containers are checked dailyand the eggs removed to a hatching trough. A male may be used to spawnseveral females.Frcunn 4&. Channel catfish spawning pens. Note spawning receptacle (arrow).(Fws photo.)