See K.C. Hanson's article, "The Galilean Fishing Economy and the Jesus Tradition," a very thorough discussion of the economics of the Galilean region in the context of the Roman occupation.
The first century Galilean fishing economy was not a "free market." This lake belonged to Caesar. (The Sea of Galilee was also known as the Sea of Tiberias.) Caesar said who could and could not fish on his lake.
Fishermen had to get a license from the local tax collector, quite likely in Capernaum. Capernaum had both a tax office, and a major harbor. In fact, it was probably the major fishing village on the Sea of Galilee. The tax collector might well have been Matthew, in fact, who was a tax collector in Capernaum.
Licenses tended to be sold to associations of fishermen, quite often based in kinship--James and John, for example, who had a "kinship-based fisherman's association," as did Peter and Andrew. Incidentally, all four of them were from Capernaum.
The fishermens' relationship to the larger economy was quite complicated. The main dynamic was the flow of money from people on the bottom to the people on the top. There were taxes on almost everything. The total level of taxation approached 50%. (Hanson has an interesting diagram of those relationships.)
Jesus spent a lot of time in these fishing villages, and seems to have used Capernaum as something of a "base" for his campaign. Various other fishing villages, some also with harbors, are mentioned in the gospels. Jesus spent time in Bethsaida, Gennesaret, Magdala (his girlfriend's hometown), Gerasa, Tyre, and Sidon.
In terms of social pecking order, fishermen would have been about one notch up from land-less artisans, but half-a-notch lower than a landed peasant. The number of landed peasants was declining as a result of Roman tax and commercialization programs, thus driving more and more people further into poverty.
Hanson doesn't say this, but some of these newly land-less peasants may have been trying to work their way into the fish economy. This may have had the effect of driving down wages, and perhaps, in some cases, increased competition for fish.
It makes you wonder what particular characteristics of Jesus' appeal would have attracted fishermen? His radical critiques of the Temple perhaps? The Temple bureaucrats and rich families of Jerusalem generally looked down on the boorish plebians of the northern hinterlands.
His crafty subversion of Roman imperial theology likely had appeal as well. It's not for nothing that Jesus' stories often refer to debt and have a rich or powerful person as the villain of the story. In a declining economy, which was the result of Roman occupation, such a message would have had some resonance.