What primarily governs the movement and direction of ocean currents?

The movement and direction of ocean currents are primarily influenced by wind patterns and Earth's rotation. Winds create surface currents by exerting force on the water, leading to the establishment of patterns that circulate water across the ocean. The Coriolis effect, resulting from Earth's rotation, further modifies these surface currents, causing them to curve rather than move in straight lines.

In addition to wind, other factors like temperature and salinity also play roles in the vertical mixing of water and the formation of deep ocean currents, but wind and the rotation of the planet are the primary drivers of the overall movement of surface currents. This dynamic system leads to the complex patterns observed in global ocean circulation, which significantly impacts climate and marine ecosystems.

The other choices suggest simplistic or unrelated concepts. Gravity alone does not dictate the currents; instead, it influences ocean water's deeper movements but is not responsible for the surface currents dominated by winds. Temperature alone does affect water density and stratification but does not govern the currents directly without wind influence. Fish migration patterns do not influence the vast movements of ocean currents but are rather a response to the conditions created by those currents and other environmental factors.