Explain the term hypophysation.

Hint: Fishes are limbless and cold- hearted vertebrates who use gills for respiration. The term hypophysation is related to fishes.

Complete Answer:
- Hypophysation is one of the types of methods that is used in fish breeding technique. In this technique, fishes are injected with an extract which is prepared from the pituitary gland. This technique also includes the induction of various gonadotropin hormones in the body of the fish needed for breeding purposes.
- Gonadotropins play an important role in increasing the frequency of breeding in the fishes. This method is beneficial to promote the reproduction in fish in the condition, where spawning is not favourable. Spawning is the process by which fishes deposit or release eggs.

Advantages of hypophysation are as follows:
i. The carps breed in rivers but not in captivity. But by hypophysation, carps can be made to breed in captivity.
ii. Through hypophysation, healthy and pure seeds can be produced at any time in the year. These seeds can be used for fish farming, which ensures desired quantities of carps.

One of the drawbacks of hypophysation technique is that it lacks standardization of the pituitary material.

The hypophysation technique can be used for obtaining more fish from an individual fish through artificial propagation involving stripping after hypophysation. Therefore, as compared to other propagation techniques, more fish can be obtained through hypophysation.

Note: Some of the species of fish such as Catla, Rohu, Marigal, Silver Carp, Grass Carp, and Common Carp are cultivated through induced breeding techniques.