Question

what is counter current flow in fishes​

Answer 1

Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae. The arrangement of water flowing past the gills in the opposite direction to the blood (called countercurrent flow) means that they can extract oxygen at 3 times the rate a human can.

Answer 2

Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae. The arrangement of water flowing past the gills in the opposite direction to the blood (called countercurrent flow) means that they can extract oxygen at 3 times the rate a human can.