This is a technique used by fishermen in rivers. It involves a gill net, chosen for a specific size or species of fish, which is stretched across a stream or river as a barricade. Fish that are swimming upstream will hit the net and become ensnared in the thin nylon strands of the net.
Ali is practiced by fishermen who fish for personal consumption and also to sell fish in local markets.
The Ali fishing method has the potential to harm the river system if the nets are used often. Fish that migrate from the ocean up streams to spawn are caught and therefore the fish population may consequently be reduced.