Raining fish bring life to ponds

I HAVE made a number of garden ponds in my life and, because I’m interested in such things, I’ve always kept a close eye on the plants and animals that colonise them.

It’s remarkable how rapidly life appears in a new pond. In most cases there are logical explanations for how it gets there. Many pond insects, like water beetles and water boatmen, can fly. They don’t do it very often but, often once a year and often at night, they reveal their wings and fly off in search of a new body of water to colonise.

Then if you collect anything from a wild pond — perhaps oxygenating water weeds or frog spawn, you may inadvertently introduce other animals, or at least their eggs or tiny larvae. There is also a theory that water birds transfer fragments of weed, sometimes with eggs attached, when it gets tangled in their legs — though most of the ponds I’ve built have been too small to attract water birds.

But there are some examples of colonisations that don’t fit any of the nice, neat explanations. I’ve known Gammarus, the freshwater shrimp, appear as if by magic in a pond. And there are a few other examples of animals, plants and even fish that appear to arrive spontaneously.

I’ve become convinced that sometimes they come down in the rain. At first sight this seems ridiculous. But the phenomenon of quite large animals raining down from the sky is rare but well authenticated. A quick internet search came up with 10 examples of it raining fish, in various parts of the world between 1861 and 2012, three examples of showers of frogs or toads — in 2005 it happened in Serbia, in June 2009 it went on for a month in part of Japan and in 2010 it happened twice in Hungary. Various other creatures seem to have dropped from the clouds, including jellyfish, spiders, worms and snakes, tomatoes and coal.

The spread of camera phones has helped authenticate it. The trouble is there is no good scientific explanation for how it happens. The usual theory is the animals are sucked up into the atmosphere by a tornado or a waterspout (which is a tornado travelling over water). Unfortunately many meteorologists are not happy with this. They say waterspouts are composed of finely condensed water vapour and have no ‘sucking’ ability and although tornadoes can lift large objects they just fling them out again on ballistic trajectories and don’t carry them for distances.

So there’s a mystery. But there are credible accounts of frogs and fish raining out of the sky so it’s easy to imagine that it could happen quite frequently with small seeds, eggs or larvae.