Bonefish

• With fish, gaseous exchange takes place in the gills. Four gills are found in the gill chambers on either side of the head, with gill slits opening to the exterior
• The gills consist of a large number of filaments, increasing the surface area. The filaments have thin walls and are kept moist by water flowing over them. The gills are richly supplied with capillaries
• As the fish swims, water flows into the mouth and over the gill filaments. Dissolved O2 in the water diffuses into the blood capillaries. CO2 in turn diffuses from the capillaries into the water. O2 rich water leaves through the gill slits. Gill slits are covered by gill covers that protect the underlying gill filaments