Voyages of exploration did usually have some basic fishing gear. But large scale fishing from a boat usually requires specialized equipment. Stuff that would take up an unreasonable amount of space. So in general they had to make do with supplies they brought or with what they could trade for.

Even if they had brought specialized equipment the open ocean is a terrible place for fishing. With our modern technology most fishing today is still done relatively close to shore. The reason for this is that open ocean is relatively devoid of life. You can look at maps like this showing chlorophyll concentrations and see where the relative deserts of the oceans are.

When near shore Magellan's crews did fish. They pulled a lot of fish out of the Straits of Magellan for example. But when they crossed the Pacific they crossed right through the middle of the South Pacific Gyre, an area almost entirely devoid of fish (and with little wind). They attempted to catch fish while in the Gyre; but it was like hunting in the Sahara, slim pickings.