There have been several reports of "raining fish" where fish fall from the sky (usually during a rain storm). An example such as this 2010 video from National Geographic seems unlikely at best.
Has this really happened, or is it a popular hoax?
If it happened, was the associated rain salty (sea water)? Were the fish still alive?
Yes.
As published in "Do Fish Fall from the Sky?" Science vol. 109 page 402,
On October 23, 1947, biologist Alexander Dimitrivitch Bajkov, PhD was eating breakfast with his wife at a restaurant in Marksville, Louisiana when the waitress told them that fish were falling from the sky.
...J. E. Gremillion, and two merchants, E. A. Blanchard and J. M. Blouillette, were struck by falling fish as they walked to their places of business at 7:45 am. There were spots in the vicinity of the bank (a half block from the restaurant) averaging one fish per square yard. Automobiles and trucks were running over them. Fish also fell on roofs of houses.
They were freshwater fish native to local waters, and belonging to the following species: Large-mouth black bass (Micropterus salmoides), goggle-eye (Chaenobryttuis coronarius), two species of sunfish (Lepomis), several species of minnows and hickory shad (Pomolobuts medfocris). The latter species were the most common. I [Bajkov] personally collected from Main Street and several yards on Monroe Street, a large jar of perfect specimens, and preserved them in Formalin, in order to distribute them among various museums...
The fish that fell in Marksville were absolutely fresh, and were fit for human consumption. The area in which they fell was approximately 1,000 feet long and about 75 or 80 feet wide, extending in a north-southerly direction, and was covered unevenly by fish. The actual falling of the fish occurred in somewhat short intervals, during foggy and comparatively calm weather. The velocity of the wind on the ground did not exceed eight miles per hour. The New Orleans weather bureau had no report of any large tornado, or updrift, in the vicinity of Marksille at that time. However, James Nelson Gowanloch, chief biologist for the Louisiana Department of Wild Life and Fisheries, and I had noticed the presence of numerous small tornadoes, or "devil dusters" the day before the "rain of fish " in Marksville. Fish rains have nearly always been described as being accompanied by violent thunderstorms and heavy rains. This, however, was not the case in Marksville...
Bajkov goes on to refer to the work of E.W. Gudger who published four articles describing 78 instances of fish falling from the sky, and concludes:
There is no reason for anyone to devaluate the scientific evidence. Many people have never seen tornadoes, but they do not doubt them, and they accept the fact that wind can lift and carry heavy objects. Why can 't fish be lifted with water and carried by the whirlwind?
An example of the Gudger's work to which Bajkov refers is:
More Rains of Fishes Journal of Natural History Series 10, vol. 3, pages 1-26. Gudger's title is given as associate of ichthyology, American Museum of Natural History.
This article was a follow up on Grudger's Rains of Fishes Journal of the American Museum of Natural History vol. 21, pages 607-619
Time Magazine 17 November 1947 reported the fish falling in Marksville with only one sentence:
Law of Compensation: In Marksville, La., hundreds of little fish inexplicably fell from the sky on poultryless Thursday.
See also the United States Fish and Wildlife Service publication Rains of Fishes for more fish falling events and references.
update:
29 December 2021, another fish raining event in Texarkana, Texas https://local12.com/news/offbeat/video-captures-fish-falling-from-the-sky-in-texas-terarkana-storm-raining-hailing-windy-national-weather-service-water-spout-cincinnati-ohio
Apparently gulls dropped lamprey in various locations in Fairbanks, Alaska in 2015.
The Alaska Department of Fish and Game in Fairbanks has been fielding calls this week about eel-like fish falling from the sky.
The calls have been about strange-looking fish, identified as Arctic lamprey, being found in odd locations on land in the community.
