A. Forces Influencing Ocean Currents:
1. Planetary Winds:
- Trade Winds and Westerlies push surface water in consistent directions.
- Example: North Equatorial Current driven by Northeast Trade Winds.
2. Coriolis Force:
- Caused by Earth’s rotation.
- Deflects currents right in Northern Hemisphere, left in Southern Hemisphere.
3. Temperature & Salinity Differences:
- Cold, saline water sinks; warm, less saline water rises.
- Drives thermohaline circulation (global conveyor belt).
4. Earth’s Rotation & Shape:
- Rotation causes gyre formation; shape affects boundary currents.
5. Gravity & Tides:
- Tides cause periodic vertical movements; minor role in large-scale currents.
6. Ocean Basin Topography:
- Mid-ocean ridges, trenches, continental shelves redirect flow.
B. Role in Global Fishing Industry:
1. Nutrient Upwelling Zones:
- Cold currents (e.g., Peru Current, Canary Current) cause upwelling.
- Bring nutrients from seabed → phytoplankton growth → fish breeding zones.
- Example: Humboldt Current supports Peru–Chile anchovy fisheries.
2. Mixing Zones:
- Where warm and cold currents meet → high biological productivity.
- Example: North Atlantic Drift meets Labrador Current near Newfoundland Banks (major cod fishing area).
3. Temperature Regulation:
- Ocean currents maintain optimal temperature zones for various fish species.
4. Migration & Breeding:
- Fish follow specific current patterns during breeding/migration.
- Example: Tuna, salmon navigate via ocean temperature gradients.
Conclusion:
Ocean currents, driven by complex geophysical forces, directly influence marine ecosystems and fishing zones, making them vital to the global fishing economy and coastal livelihoods.
