1. The Problems of Fish Oceans 11

2. Introduction Seawater may seem like an ideal habitat, but living in it does present difficulties. –How can fish best move through water? –Why don’t fish sink? –How can fish breath underwater? –How do they deal with the salinity of seawater? –How can predators be avoided?

3. Movement Shape and Propulsion: How can fish best move through water? –Fish usually have a streamlined shape (this reduces energy loss to drag) –Faster swimming fish have tapered, torpedo like body plans –Swimming occurs by S-shaped waves that pass through body. *FYI - Swordfish and Marlin can reach speeds of 120km/hr! http://www.youtube.com/watch?v=Viu9gql djrc&feature=relatedhttp://www.youtube.com/watch?v=Viu9gql djrc&feature=related

4. Bluefin Tuna

5. Maintenance of Level: Why don’t fish sink? –Fish are more dense than water –Swim Bladders provide enough buoyancy to offset the animal’s weight (only found in bony fish) –The amount of gas in the bladder changes with depth

6. Swim Bladder

7. Gas Exchange: How can fish breath underwater? –Fish take in water (containing Oxygen) in through their mouth –Water is pumped past fin gill membranes (where oxygen is picked up and carbon dioxide is dropped off) –Water exits through gill slits –Circulatory system transports blood through body

8. Gills

9. Osmotic considerations: How do they deal with the salinity of seawater? –In bony fish special glands in gills excrete excess salt –Sharks and rays supplement internal fluids with urea (occuring in bodily fluids as a product of protein metabolism) Osmotic: The tendency of water to pass through a membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side.

10. Defence: How can predators be avoided? –Sight and hearing are usually very well developed –Lateral line system can detect low-frequency vibrations –Camouflage: http://www.youtube.com/watch?v=HSPptPhbFVc http://www.youtube.com/watch?v=HSPptPhbFVc –Countershading –Schooling behaviour *FYI Flying fish can simply disappear by accelerating rapidly, leaping into the air and spreading their fins to act like wings! http://www.youtube.com/watch?v=gAjzH0vWSIA