According to various Iranian media sources in late April 2018, there was a fall of fish in the town of Golpayegen, a city in Isfahan Province. Golpayegen is located around 400km south west of Tehran.
The original news sources are short on detail, but the reports state that the fish were discovered on a Golpayegen roadway after rain. An accompanying video shows many small fish, some alive, distributed along a section of paved highway. People appear to have stopped their vehicles to collect the live fish. There is water across the road so there may well have been recent rain. There is also an audio commentary – any readers speak Persian?
Farda News stated that speculation around the fall did include the possibility that they were from a truck that had overturned. The Director of Agriculture in Golpayegan is quoted as saying the fish could have been part of a shipment of fingerlings to another city but local traffic police were not able to confirm that there had been an accident. The video shows no sign of an overturned vehicle, and the fact that some of the fish were still alive means it must have been taken relatively soon after they were distributed.
Live fish found distributed along a road are far more likely to have come from a vehicle than from the sky. The fact that most of the fish are located on only one side of the road also supports the idea that the fish may have been released from a vehicle.
I think this case can be safely called a false fish alarm.
UPDATE 4/5/18. Reviewing the video, I notice there appears to be a large truck parked further down on the highway. Could this have been the one that was transferring the fish when they lost part of their load?