"J said, A wise fisherman cast his net into the sea. When he drew it up it was full of little fish. Among them he discovered a large, fine fish. He threw all the little fish back into the sea, and he chose the large fish. Anyone here with two good ears should listen."
The odds are good that this saying is not about telapia. Jesus is a wise fisherman and teaches with the intent that the disciples become more like him ... rich in wisdom. So in this saying he is reaching out to each of us. He is explaining a crucial portion of the path of wisdom. Jesus was familiar with Jewish teachings and in the deeper temple lessons, a fish corresponds to the imaginative intelligence.
In speaking about fishing Jesus awakens the imaginative faculty of the listener (they can each imagine themselves fishing, it was a common activity on the Sea of Galilee) and enlightens them about an aspect of how their mind works.
Jesus is explaining what happens when we observe ourselves. We can take time to be self-aware, observant of the ebb and flow of our thoughts. Every thought is either born of love or born of something else e.g. fear guilt.
When we observe the flow of our thoughts for awhile we may see an abundance of thoughts of the "something else" variety .... these are like the little fish. Amidst these will be one of our true thoughts, one whose genesis is love, like a gift from the Mind of God ... this is the big fish.
To toss the little fish back means Jesus is saying that all we need are the God thoughts, and we can ignore all the other thoughts, just toss them away. These something else thoughts are deceptive and may lead us astray for awhile .... away from peace.
The last sentence of the saying is colloquial, a phrase that means "this is important", or "pay attention", etc.
The wise fisherman is ever alert to the way he is thinking, and seeks always to think with God, so that more often, his thoughts are born of love.
Through our growing understanding of these sayings Jesus helps us become wise fishermen too. This saying does not mention why there are so few big fish and so many small fish, that is likely covered in another saying.
David