The fish and lamb predate the cross as logo for Christianity. It is very interesting b/c mainstream Christianity believes in the cross as the central tenet of Christianity. The nature of Jesus and Christ seem more impt than a reminder of one miracle. I saw both at the Vatican museums. We toured the catcombs under St. Peter's and I saw fish there but not crosses.
It is more than one fish so it had to have special meaning to them as a community. We don't know so much about the earliest forumulations of Christianity. Paul seems to be a cross man; a Trinity fashioner. James appears to be Jesus as not quite God. The leap from a Jewish conception of God as transcedent to the later view of immanence and transcedence must have been gradual. It is of central importance to Jews and Christians yet the gospel writers don't address it. There are some very early credal statements in Paul's authentic letters.
Preaching door to door does not address whether Jesus was the son of man. Insurance salesmen and kitchen installers go door to door. The apostles went from being mediocre and none too bright in the gospels to martyrdom within a few years. The most fundamental questions humans address universally are raised. Yes, JWs are known for invading privacy and disturbing the peace of people along with constantly changing wacko positions. Jesus does return to judge the living and the dead. He needs to set examples of efficacy. Mother Theresa and those who toil in prisons, those who feed the hungry and heal the sick with courage are present. Some JW door knocking zombies are also being judged. Which one followed Jesus' express commandments? What you do for the least of these, you do for me! I've been in hospices. The JWs don't care for their least, let along the least of Jesus.