Catena Aurea on Mark 6:45–52: Bede

But it is with reason that we wonder how Mark says, that after the miracle of the loaves the disciples crossed the sea of Bethsaida, when Luke relates that the miracle was done in the parts of Bethsaida [Luke 9:10], unless we understand that Luke means by the desert which is Bethsaida not the country immediately around the town, but the desert places belonging to it. But when Mark says that they should “go before unto Bethsaida,” the town itself is meant.

It goes on: “And when He had sent them away, He departed into a mountain to pray.”