Science Questions

Does lightning fry fish?

Mon, 10th Mar 2014

Part of the shows Does lightning fry fish? and Turning the Tide on Flooding


Hazel Barraclough asked:

When lightning hits the sea or a lake, do any fish nearby get electrocuted?


Hannah -   So, why donít we see floating electrocuted fish following a thunderstorm?  First up, some facts.  Lightning is a massive electrostatic discharge, the sudden flow of electricity. 


During a thunderstorm, regions of positive or negative charge build up within or between clouds and the surface of the planet.  This charge is eventually discharged by a lightning flash or strike, carrying a whopping 30,000 amperes of current and transferring 500 megajoules of energy.  This is the equivalent energy striking in a split second as a colossal 1,400 100-watt bulbs running for an hour. 

So, since humans are concerned about being frazzled when lightning strikes on land,

aren't fish worried in water?  Over to the expertÖ

John Jensenius -   My name is John Jensenius.  I'm a lightning safety specialist with the National Weather Service in the United States.  Really, when you get down to it, you have to look at what happens when a thunderstorm develops and what happens just prior to the lightning strike.  There's a charge that builds up in the cloud and there's an opposite charge that builds up on the surface of the water.  So, when lightning flash occurs, the discharge discharges along the surface.  So, the effect of the lightning is pretty much contained to the surface of the water and in fact, the fish that are swimming below the water are safe.  They're completely unaffected by the lightning.

Hannah -   And listener Erik Sandberg agrees.  He says that the lightning electricity

will mostly stay on the surface of the water.  He also says that he thinks itís to do with the fact that the water is such a good conductor and the electricity will quickly be dispersed or spread-out to the surrounding water close to the surface.

John Jensenius -  Well, [salt] water is a good conductor of electricity, and thatís one of the reasons that the charges can move to the surface of the water and it is true when lightning strikes the water that discharge literally spreads out along the surface.  Of course, with the fish below, they should be safe.


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