Do you recognise this? It is freshwater eel steamed with fermented black soybean (豆豉). I thought 豆豉 were made with black beans (黑豆) and were naturally black. But my parents said they were made with soybeans which were yellow. They only turned black through the fermentation process.
In any case freshwater eel steamed with fermented black beans (豆豉蒸白鱔) is very tasty. The flesh is white, fatty, soft and succulent. There are very few bones, and whatever bones they have are quite soft. So you can eat essentially the whole thing, with very little wastage. Really good.
I heard that these freshwater eels are actually born in sea water. When they grow bigger they swim up rivers to live. Then they return to the sea to give birth. Very strange.