Dear Aspirant, to become a fishery scientist, the sound knowledge of biology along with interest is very important. A person with a back ground of physics, chemistry or mathematics or other non biological subjects is not going to help in understand the courses of Fishery sciences.
Why it is so, let me explain about the various courses of fishery sciences at masters or graduation levels.
The courses in masters degree are Fish nutrition, fish breeding, Fish genetics, Post harvest technology, Fish biotechnology, Inland aquaculture, Fish pathology and immunology, Fish Microbiology and others. from these subjects it is clear, that all the subjects have biology in it.
Therefore, it becomes imperative to have a knowledge of biology or a basic understanding of biology.
Here biology means the Zoology, the study of animals, Biology background is required at the level of 10+2. After that some detail studies of zoology is essential in bachelor degree program.

The sound understanding of biology is also very important to understand all the courses of Fishery sciences.
The course of Fish breeding, here you have to study the breeding seasons, breeding possibilities and rearing of eggs. In Fish nutrition, the various types of nutrition, their effect on fish growth, behavior and sexual activities, the nutrition should be cheap and easily available and should not be toxic to any aquatic animal or organisms. Fish genetics, here the total heredity methods of fish, this is studied and done to improve the varieties of fishes, this is some what similar to breeding program.
In most of the fishery courses, one has to study the urogenital, circulatory, respiratory and nervous system, therefore a basic or deep understanding of biology is very important. Moreover, the interest in biology subject is above all.
A fishery scientist has to improve the existing species of fish for more size, more eggs production, therefore, a person with sound understanding of biology can easily and successfully carry out this job. The pathology, microbiology, biotechnology and immunology aspects of fishery sciences also have biology in it. A person without understanding of biology will not be able to understand these courses and subjects.
If you want to pursue higher education in Fishery sciences or you are planning to start your career in Fishery sciences, then you should have a sound knowledge and clear understanding of biological and allied subjects along with great interest in it...