Physiology of Finfish and Shellfish (2+1)

2.1.15. Mechanism of respiration or Ventilation of gills

For respiration, a continuous current of water is maintained through the buccopharyngeal cavity. For this, water is sucked into the buccal cavity and expelled through the external branchial aperture. By inhalation and exhalation of water in the buccal cavity causes purification of blood.

Fishes use two different methods for keeping a continuous supply of new water available, one is double pump system which is complex and the other ram ventilation is very simple.