The Mystery of 'Sudden' Appearances of Fish in Isolated Ponds

 Thank you Ed

I am glad you concurred with me  if the fish were insects, beetles, birds, bees, butterflies and all winged creatures they can get to any place just by flying

But the  fish  I was talking about cannot fly like birds and the bees to evolve as a separate allopatric speciation from the sea tens of kilometers away into an isolated pond.

 It may happen if the original river with fish inside is cut off to form an ox bow lake as in the example of Lake Nagugabo where a separate species of coloured-cichlid fishes mingling with the original species of fishes are found.

But my question is, do river fish evolved from sea-fish? My thought on this is, must all fishes including freshwater river fish originally come from the sea? They swim up the river mouths upstream into the river and evolved as separate species of freshwater fish from their original salt water fish, and over many millions they began to adapt into speciation of freshwater fish.

I am unsure of European eels you mentioned that can travel long distances on land. The best I know are the mudskippers we find here in the tropics in the delta of rivers and mangrove swamps.

They can skip and glide over short distances on the wet mud outside the water. But most fish cannot live outside water.

The fishes I saw in the artificial trenches and dug-up ponds are not those large ones we find in the sea or rivers but just tiny little ones. They look like small anchovies and tiny fries

How did they got there is a little strange to me. I can understand if there was already an existing natural pond with thriving fish in it lying next to the artificially-dug one

In that case, the existing fish in the already existing pond could have jumped into the next trench or pond after the rains filled them up with water, or in the case of extremely heavy rain both ponds will be flooded for the fish to swim across

But there was no other natural pond beside it. The nearest river that I knew is tens of kilometers away. How could any fish “fly” like the birds and bees into the recently water-filled trench?

I also understand from National Geographic documentaries or on BBC Natural History, or in Animal Planet shown here on television presented often by Sir David Frederick Attenborough that certain fish such as salamander fish can survive in dry mud for months by secreting a mucous covering as you said, but those pond fishes I saw. They  were not the same or lung fishes

They just  mysteriously appear,  unseen and untouched by humans in a deserted place.

The experiment of Louis Pasteur’s that proved that spontaneous generation of microorganisms to spoil a broth was not possible in an artificial environment inside a laboratory flask under the daily watchful eye of scientists  is not the same as in a natural open and windy  environment on the soil where rains and sunshine fall.

Surely the earthworms and other small primitive soil creatures that lived there cannot have evolved into an entirely new and unrelated species (fish) within months.

I just cannot understand how these tiny aquatic creatures got there unseen by humans or carried by other animals who did not even go there???

Often even in the wetlands and swamps or another open place here in the tropics where rains fall and often flooded the area, and months later you can see tiny water creatures and slimy water weeds creeping there.

My strong feeling is, evolution of all living creatures is taking place spontaneously and constantly all the time, ever since creation or the beginning of time and evolution while others and old ones less adapted die out. It looks to me like some kind of life cycle on Earth. I am not too sure! Maybe we can have this discussed in our next academic forum

Lim ju boo

University of Cambridge