Fiqh-us-Sunnah - 3.53

Hadith 3.53.1

Most scholars stipulate that zakah is not payable on anything extracted from the sea, such as pearls, corals, chrysalite, cachalot's ambergris, fish, and so on. There is, however, a report from Ahmad that if the amount extracted reaches a nisab, then zakah is due on it. Abu Yusuf agrees with him in the case of pearls and cachalot's ambergris. Ibn 'Abbas holds that there is no zakah of cachalot, beacause it is an object thrown out by the sea. Jabir said that there is no zakah on cachalot, but that it is a free spoil for anyone who finds it.

Hadith 3.53.A

Acquiring Property Through Profit or Increase

When a person acquires property and it stays in his possession for a year and constitutes a nisab, and he has no other property or he has similar property which has not reached a nisab except when the acquired property has been added to it, then the year hawl of zakah becomes applicable to it from the time of its acquisition. The zakah will be payable at the completion of the hawl. In such a case, the acquired property may be classified in any of the following categories: The acquired holdings increase in value either by profits from trade or by an increase in animal production. These kinds of holdings qualify themselves for the application of the hawl and zakah. For the individual whose merchandise or animals constitute a nisab and whose business also makes a profit or whose animals reproduce during the course of the hawl, he should count the original and additional property as one for the purpose of zakah. There is no dispute about this among scholars.
As for the acquired property which falls under the same category as the attained nisab but is not derived or generated from it--that is, it was acquired through purchase, gift, or inheritance-- Abu Hanifah holds that this may be combined with the nisab in order to become a part of it with regard to the hawl and payment of zakah. Thus, the principal property and the profits are collectively taxable.
Ash-Shaf'i and Ahmad suggest that newly acquired property be combined with the original one for the purpose of attaining a nisab and that a new hawl has to be assumed for it--whether the original consists of cash or animals.
For example, if someone has 200 dirhams and manages to acquire another 200 dirhams during the year, he should pay zakah on both at the completion of the hawl which will begin to roll at the acquisition of new property.
Malik's opinion is like that of Abu Hanifah's concerning animals but like Ahmad's in regard to gold and silver.