Fish Breeding, Hatchery Management and Seed Production
Induced breeding
Captive carps do not spawn reliably without a cue. Hypophysation uses pituitary extract from a mature donor, typically at 5-10 mg/kg for females, with a lower male dose; synthetic preparations such as ovaprim or HCG are alternatives. A preparatory dose may be followed by a resolving dose; the latency period depends on temperature and species.
Hatchery operations
Select gravid females and milt-flowing males; inject; keep broodstock in flowing water; strip or allow natural spawning; incubate eggs in jars or troughs; transfer spawn to nursery ponds. Nursery ponds are small, weed-free and fertilized to produce rotifers; rearing ponds follow for fry to fingerling.
Worked example
A 3 kg female is to receive pituitary extract at 6 mg/kg. Dose = 3 x 6 = 18 mg. If each donor gland yields 2 mg, 9 glands are needed. If the male dose is one-third, prepare 6 mg for a 3 kg male. Reasoning: dose scales with body weight, not with pond volume, and donor glands must be counted before injection.
Traps
- Injecting females and males at the same dose.
- Stripping before ovulation: eggs should run clear and granular.
- Ignoring temperature when predicting latency.
- Mixing spawn from different species or batches.
- Stocking spawn directly into an unfertilized pond.