The tuna have acquired a Satellite counter measure that blocks readings from the sea surface.
The technology is marginal and the Sea surface shield is only operational for a few days at a time.
The days that the shield is least effective is on days with no clouds, it has been found the tuna use the clouds somehow to power the shield.
Just having some fun!!!!!
It is sometimes hard for me to see the clear skies outside and believe that the clouds are that thick all over the water. There might be other situations that obscure or block the readings. Maybe someone has info on this.