[AS3] Need help with collisions

Hello, I’m fairly hopeless at flash and I need help! I’m trying to create a virtual life simulation of some fish. They move randomly around the stage and when they collide I want something to happen. Like when the boy fish collide with the girl fish, they reproduce, or when a boy fish collide with another boy fish, one “dies”.Could someone please tell me how to achieve this? I’ve attached my code (advice on how to clean that up too would be greatly appreciated!)Thanks.