There is no sorting out of the fish at the time of their being caught. It is only after the net is full and drawn ashore that the sorting takes place. The good fish are kept and the bad are thrown away.
In the parable of the householder, both the new and old are affirmed. However, the old, which is valuable, is presented in a new light and therefore seen in a new way. The fact that the order of the words is “new” and “old” is an indication that the new is to be used to interpret the old and not the other way around.
If the sorting were to take place now, would you be kept or thrown away? What will you do to ensure that you are kept?