Unlike many other businesses, income in catfish farming is periodical except you have a big farm where you can sell regularly (weekly/monthly). However, some of us that sell two to three times a year may need another source(s) of income to meet our countless needs that will not wait for long period of time to be met.
In my own opinion, as a small or large scale catfish farmer, you need another business that can support your interest in catfish farming. Besides, there is no crime in making more money especially in a business that compliments your main business. Also you will have something to fall back on when you meet with major challenges like glut in catfish market.