Assamese Ujan uthicheA phenomenon during the monsoon, when freshwater fish start to breed after the first showers. When this happens, mature fish swim up to the surface of the water bodies, making it very easy to catch them.

Literally, it means the river/pond is swarming with fish because when they want to breed, they come to the surface, making them look voluminous. But “uzan uthise” means not just the swarming of a large number of fishes to the surface, but also their behaviour during breeding.