Mark 1:19

‘And going on a little further he saw James the son of Zebedee, and John his brother, who also were in the boat mending the nets, and immediately he called them, and they left their father Zebedee in the boat with the hired servants and went after him.'

Comparing with Luke we can gather that James and John had returned to shore after assisting with the large catch. Then they had gone back to their nets, leaving Simon talking with Jesus. Now Jesus approached them and called them too. The unconscious testimony of the eyewitness is found here. The cost and poignancy of the situation is made obvious. The father is left with only the hired servants, and the business they are leaving is a prosperous one, for fish was the staple diet of the people. Yet they followed immediately and willingly. The impact and authority of Jesus is made clear. Note that here it is not said that they left their nets. Those remained in use by others. In their case they left their business and their loved ones.

(We note that in Mark this incident comes before that in which Jesus deals with the man with the unclean spirit in Capernaum (Mark 1:21) while in Luke it comes after. This illustrates the fact that Mark puts his material in the order which will bring home his point rather than following a detailed chronology. He wants the calling of the disciples to be described here immediately after the proclamation of the kingship. As in chapter two he marshals his material carefully. He is not writing a chronological life of Jesus, it is not ‘in order' but rather a portrayal).