What are the forces that influence ocean currents? Describe their role in fishing industry of the world.

Forces that drive currents

• Prevailing winds, especially the trades and westerlies, drag the surface and set gyres in each ocean basin.
• The Coriolis force turns moving water to the right in the north and to the left in the south, which closes those gyres and sets western boundary currents such as the Gulf Stream and Kuroshio.
• Temperature and salinity make density differences, so thermohaline flow moves deep water in a slower global conveyor.
• Continents, narrow straits, and the equator deflect and pile water, which creates coastal currents and equatorial counter-currents.
• Seasonal monsoon winds reverse surface flow in the north Indian Ocean, which is why the Somali current can flip with the year.
• Tides and storms matter locally; they do not replace the planetary wind-and-density engine.

How currents feed fisheries

• Wind-driven upwelling along eastern ocean boundaries lifts nitrate-rich water, which grows plankton and then small pelagic fish.
• The Humboldt (Peru), Benguela, Canary, and California systems are the classic upwelling fisheries of anchovy, sardine, and related stocks.
• Mixing of warm and cold currents, as where the Kuroshio meets the Oyashio off Japan, or on the Grand Banks where the Gulf Stream system meets Labrador water, creates fog, plankton blooms, and dense demersal fisheries.
• Monsoon upwelling off Somalia and the south-west Indian coast supports seasonal pelagic catches in the Arabian Sea.
• Warm currents also carry tuna and other migratory species along predictable highways that industrial fleets follow.

Industry, risk, and climate

• The world’s largest industrial catches historically clustered on these current edges, not on still tropical lagoons.
• El Niño can shut Peru’s upwelling, crash anchovy, and ripple fishmeal and food prices, which shows that the fishery is a climate-current couple.
• Overfishing, not the current, now limits many stocks; the current only sets where biology could be rich.
• For India, the monsoon current and coastal upwelling matter for oil sardine and related west-coast fisheries, while the open Bay is a different current regime.