Most of Jesus disciples were fisherman. As a matter of fact they had left their nets and their boats to follow Jesus. They had been for quite some time fishers of men rather than fish. When Jesus told this parable to these men they knew exactly what He was talking about.
It has been reported that the northern edge of the Lake of Galilee is one of the best fishing areas in all of Israel. Plants that are carried along by rapidly descending water of the Jordan River become lodged in the northern inlet of the lake. These plants attract and feed a very large population of fish. As a matter of fact some 25 species of fish have been identified in the lake. Bethsaida is located on the north shore of the Lake of Galilee. Bethsaida first of all means "House of Fishing", and second, it was the home of Peter, Andrew, and Phillip. (Jn 1:44)
Among the many means and method of fishing during the time of Jesus, dragnet fishing was an extremely effective method.The net was about 2 meters high and about 100 meters long. Corks affixed to the top of the net would keep the net afloat while the bottom of the net was weighted down. Sometimes fisherman would mount or attach one end of the net to a fixture on shore, while the boat would then travel in a semi-circle back toward the shore and the other end of the net while other fisherman "beat" the water hoping to drive fish into the net. At other times two boats were used which traveled in a semi-circle toward each other closing the gap sweeping or netting fish in the path of the net.
The fisherman would attempt to locate a school of fish and then set the net in order to net the fish. The challenge with this type of fishing is that the fisherman could not fish for specific fish; they would catch up all kinds and types of fish. Some of those fish were good and edible while others were bad and unedible. Many kinds of fish were considered unclean by Jewish ceremonial laws and could not be eaten. Fish without fins and scales could not be eaten (Leviticus 11:10) These fish would be thrown back while the good fish would be separated out and made ready for the market.
What does Jesus intend his disciples to understand with this parable? Jesus seems to use this parable to depict a day of judgement. Jesus uses this parable to teach some spiritual truths. Jesus gives us a brief interpretation of His parable. Jesus says this is how it will be at the end of the age. During the kingdom age or period, the good news will be proclaimed to all people without discrimination. Angels will come and separate the wicked from the righteous. The angels will throw the wicked into a furnace of fire. The end of the wicked includes "weeping and gnashing of teeth."
This is meant then to encourage the disciples. The gospel will be preached to all men indiscriminately during the kingdom age. Since some inhabitants in the kingdom will be in a natural body reproduction will take place. Some of those children born during the kingdom will be redeemed and some will not be. Those who are living at the end of the kingdom period and not redeemed with be removed by the angels of God.