How do you breed fish in fish tycoon

Drag fish into isolation, the blueish box at the bottom of the screen. Then simply pick up another pick and drag it t the box. The fish in isolation will now be pregnant. Dra the fish out of the box. After a while, the fish will give birth. If you hve a high enough Fsh Evironment (see 'Supplies') then the fry will grw up to be adults.