Water with very high Micro Siemens

[stonefox]

In a local businessman I buy sometimes, prawns, but there are always many who die also for others I know who buys the same place.
The last I bought, I measured microsiemens in the water and it was 5292uS - how can it be done?
I know that my microsiemens meter works, because I use it daily when I change the water in my fish tanks ..

What do they know their water?

Se attached picture.

[Mustafa]

They probably add some salt to the water. It's a common practice in aquaculture.