What are the forces that influence ocean currents? Describe their role in fishing industry of the world.
Approach · directive: “what / describe”
What it asks · Two parts: the forces that generate and modify ocean currents, and how currents shape the location and productivity of fisheries.
The question has 2 parts — answer each
- What are the forces that influence ocean currents: primary and secondary
- Describe the role of ocean currents in the fishing industry of the world
Open with · Ocean currents are large, regular movements of surface water driven by planetary forces and modified by sea and land conditions.
Cover
- Primary forces: solar heating, wind drag, gravity, and the Coriolis force, which deflects currents right in the northern and left in the southern hemisphere.
- Secondary forces: differences in temperature, salinity and density; coastline shape, sea-floor relief and seasonal winds, such as the reversing monsoon drift in the Indian Ocean.
- Mixing zones: where warm and cold currents meet, plankton-rich water supports dense fish stocks, as at the Grand Banks and off Japan.
- Upwelling: cold currents on western coasts bring nutrients up, supporting anchovy and sardine fisheries off Peru (Humboldt), Namibia (Benguela), north-west Africa and California.
- Fish movement: currents carry eggs and larvae, guide migrations, and shape fishing seasons; sea-surface temperature maps direct fishing fleets.
- Risks: El Niño weakens Peruvian upwelling and collapses catches, and warming is shifting currents and fish stocks.
Close with · Currents decide where nutrients and fish gather; sustainable management must follow these shifting ocean patterns.
Question: UPSC's CS (Main) 2022, GS Paper I — paper ↗. Approach: Minimalist IAS, checked 30 Sept 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer · 315 words (UPSC limit 250) · Minimalist IAS
Ocean currents are the regular, large-scale movements of ocean water, set in motion by planetary forces and shaped by the geometry of oceans and coasts.
Forces influencing ocean currents
- Primary forces: differential solar heating makes warm equatorial water expand and flow poleward while cold polar water sinks and creeps back; planetary winds, the trades and westerlies, drag the surface into the equatorial currents and drifts; gravity moves water down pressure slopes.
- Coriolis force bends moving water rightward north of the equator and leftward south of it, curving the flow into the great subtropical gyres.
- Secondary forces: differences in temperature, salinity and density drive slow thermohaline circulation; coastline shape and sea-floor relief deflect flow, as Cape Sao Roque splits the South Equatorial Current; the seasonal reversal of the monsoon winds reverses the currents of the northern Indian Ocean.
Role in the fishing industry
- Meeting of warm and cold currents: where the Gulf Stream meets the Labrador Current at the Grand Banks, and the Kuroshio meets the Oyashio off Japan, mixing stirs nutrients, plankton blooms and some of the world's richest cod, herring and sardine grounds form.
- Upwelling: cold currents on western continental margins, the Humboldt off Peru, Benguela off Namibia, Canary off north-west Africa and California, draw nutrient-rich deep water up, sustaining anchoveta and sardine fisheries.
- Temperature and migration: currents carry eggs and larvae and mark the thermal corridors along which tuna, mackerel and salmon move, fixing fishing seasons; fleets follow satellite sea-surface temperature maps to current edges.
- Hazards: warm and cold water meeting breeds dense fog, and the Labrador Current carries icebergs into the Grand Banks lanes.
- Instability: El Niño weakens Peruvian upwelling and collapses anchoveta catches, and ocean warming is shifting currents and fish stocks poleward, straining quotas and coastal livelihoods.
Currents decide where nutrients gather and fish congregate; sustainable fisheries must therefore track these ocean patterns as they shift under a warming climate.
Written by Minimalist IAS from facts checked at source (how we verify) — a little fuller than exam length, so every part of the question is covered; in the hall, keep the structure and trim the detail. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.