What are the forces that influence ocean currents ? Describe their role in fishing industry of the world. (Answer in 250 words)

Ocean currents are large-scale water movements driven by energy input and modified by Earth’s rotation and geography. Forces. Solar insolation heats equatorial waters, creating temperature gradients; gravity acts on density differences and sea-surface slope to produce pressure-gradient flow. Planetary winds—trade winds and westerlies—drive surface currents, while the Coriolis force deflects them rather than driving them, shaping gyres. Thermohaline circulation, caused by temperature and salinity density gradients, moves deep water globally. Continental configuration, seabed topography and friction with coasts and the seabed deflect, split or channel currents.

Fishing industry. Alongshore winds and Ekman transport draw up nutrient-rich deep water; cold eastern boundary currents such as the Humboldt/Peru, Benguela, California and Canary are associated with these upwelling zones, supporting dense phytoplankton and fish populations. Convergence and mixing zones create rich grounds: the Grand Banks, where Gulf Stream and Labrador waters meet, and the Kuroshio-Oyashio mixing zone, supporting tuna, mackerel and migratory routes. Warm currents such as the Gulf Stream and Kuroshio provide transport routes for tuna, mackerel and pelagic fish. Shallow continental shelves and tidal mixing make the North Sea and Dogger Bank productive. In India, southwest-monsoon upwelling along the Kerala–Karnataka coast sustains the oil-sardine and mackerel fishery, while the seasonally reversing West India Coastal Current and Indian Ocean Dipole phases alter this productivity from year to year. Conversely, off Western Australia the warm, poleward Leeuwin Current suppresses upwelling, keeping those waters relatively poor in fish. Climate change is shifting winds, temperature, salinity and upwelling, threatening stable fish stocks and requiring adaptive fishery management.