Finfish Breeding and Hatchery Management

Preservation of pituitary gland:
There are three methods of preservation of  fish pituitary gland.

1. Preservation in absolute alcohol :
 
● Immediately after collection, wash the pituitary  and transfer  it  to   fresh alcohol. 
● After 24 hours, wash the pituitary again with fresh alcohol  and store in fresh alcohol at room temperature in a dark place or in a refrigerator.
● Absolute alcohol dehydrates the gland,   dissolves fats and preserves it for a long time.
Attach a label bearing date of collection, name of fish, stage of maturity, etc. to the vial.

2. Preservation in acetone:
● Immediately after collection, transfer the pituitary gland to ice-chilled acetone and stored in a refrigerator for 2-3 days.
● During this period, change the acetone 2-3 times and store the gland in a refrigerator.
● Like absolute alcohol, acetone also has dehydrating and defattening effect.

3. Immediate freezing :

In this method, freeze the glands immediately by keeping them in a freezer and store in a freezer.
 
Preparation of fish pituitary extract for injection
● The pituitary gland is necessary to prepare  the pituitary extract which induces fish to breed.
● Prepare the extract just before injection and note the weight of each brooder.
● Based on the weight of all the brooders, calculate the total quantity of  glands required to be used  for extract preparation, allowing about 10%  towards wastage.
● Take the glands out of the vial and dry them using blotting paper
● Homogenize the glands in a tissue homogenizer with a suitable medium, i.e. distilled water or saline
● If acetone-dried glands are used, they can directly be taken for maceration.
● Use one-third of the medium for homogenization and the remaining two-thirds for rinsing the homogenizer and the glass rod.
● Maintain a dilution rate of 20-30 mg of pituitary in 1 ml of the medium.
● After transferring the contents from the tissue homogenizer to centrifuge tubes, centrifuge the extract at 5,000 rpm for 5-10 minutes.
● Transfer the clear supernatant solution containing gonadotropins to a beaker for injection.