Finfish Breeding and Hatchery Management

Unit 3 - Breeding of major carps

3.3.3. Preparation of fish pituitary extract for injection

• The extract preparation should be carried out just before injection.
• The required quantity of glands is taken out of vial and they are dried on a filter paper by allowing the alcohol to evaporate.
• The glands are then homogenized with distilled water or saline in a tissue homogenizer.
• If acetone-dried glands are used, they can directly be taken for maceration.
• One-third of the media is used for homogenization, while the remaining two-third is used for rinsing the homogenizer and the glass rod.
• Recommended dilution rate is 20-30 mg in 1 ml of the media.
• The extract is centrifuged at 5,000 rpm for 5 minutes.
• The clear supernatant solution containing gonadotropins is taken in syringe for injection.
  

Types of injection

Homoplastic injection: Injecting pituitary from one fish to another fish closely related to the donor fish. E.g. carp pituitary gland extract to carps.

Heteroplastic injection: Injecting pituitary from one fish to another fish distantly related to the donor fish. E.g. carp pituitary gland extract to catfish and vice versa.

Methods of injecting fish brooders

There are three methods of injecting brooders.
They are :

1. Intra-muscular injection:

• It is administered into the muscle on the caudal peduncle or behind the dorsal fin, but above the lateral line.
• It is most effective, convenient, simple and less risky.
• It is widely practiced.

2. Intra-peritoneal injection:

• It is give through the soft regions of the body, generally at the base of the pelvic fin or the pectoral fin.
• It is risky as it may damage the gonads or liver.

3. Intra-cranial injection:

• In this method, the injection is given through the cranium and is also risky as it may damage the brain.
• The pituitary extract is administered through a glass or disposable syringe, 2.0 ml capacity, having 0.1 ml graduation.
• The size of the needle depends upon the weight of the brooder to be injected.
• Needle number 22 is used for fish weighing 1-3 kg, No. 19 for larger fish and No. 24 for smaller fish.
• When two injections are given, one is given on the side that did not receive the first injection.