Osteichthyes • Means fish with bony skeletons • There are over 20,000 species of bony fish
Where Do Most Fish Live? • Most fish live in the epipelagic zone
Why do fish move? • To increase their chances of survival • To help them reproduce • To find food and shelter • To get oxygen • To migrate • To avoid predators Fish want to use as little energy as possible to get what they need
What Slows Fish Down? • Frictional drag – the rubbing of the surface of a fish’s body against the water slows it down. • Ideal shape to reduce drag is a sphere
What Slows Fish Down? 2nd Type of Drag • Form Drag – is caused by cross-sectional area pushing through viscous (THICK) water • To reduce form drag the fish should be like a long cylinder
What Slows a Fish down?Type of drag 3 • Turbulance – caused by movement of the natural currents in the water. • The best shape to reduce this drag is like a torpedo, 4.5 times the objects diameter.
Types of Fins • Tail Fin (CAUDAL FIN) • Paired Fins (PECTORAL and PELVIC FINS) • Medial Fins (DORSA and ANAL FINS)
PRESSURE AND DEPTH • The weight of air pressing on an average adult person is about 8 tons. If this pressure were to be suddenly removed from us our blood would boil and we would die in seconds.
How a Fish Swims • A fish swims by contracting the muscles on one side of its body like a wave along one side of its body going from head to foot.
Caudal Fins • Caudal fins have different shapes • 1. Homocercal --> Top and bottom halves the same size • a. Rounded (Low A.R.) • b. Truncate (Intermediate A.R.) • c. Forked (Intermediate A.R.) • d. Lunate (High A.R.) • 2. Heterocercal --> Top half different size than bottom half
Types of Caudal Fins • Heterocercal – often found on sharks
Types of Caudal Fins • Some shapes help the fish swim fast like the lunate shape while others make the fish swim slow but turn well
Paired Fins • Help the fish turn and stop
Medial FinsDorsal and Anal Fins • Help prevent the fish from spinning and keep it stable in the water
Measuring Fin Efficiency • Aspect Ratio = (fin height)2 / fin area Higher aspect ratio = faster fish
Movement, Streamlining, and Speed • The speed limit of a fish is determined by the viscosity or thickness of the water • Streamlining of the fastest swimming fish (ex. Tuna) reduces turbulence • Eyes are flattened against the head and male sex organs are usually internal • Barracudas can reach speeds of 40 km/hr • Yellowfin Tuna can reach speeds of 45 km/hr • Larger Tuna can reach 110 km/hr
Cruising Speed • Cruising speed for fish is about: • 1 or 2 body lengths per second (BL/sec.)
Kinds of Muscle in Fast Swimming Fish • 75% of the total body mass of fast swimming fish like tuna is muscle • There is a greater percentage of red muscle than white muscle • Red muscle contains myoglobin, a pigment that attracts oxygen. • The power output of red muscle is 6 times that of white muscle
Water Viscosity • Water viscosity is the thickness of water caused by the sticky cohesion of water molecules to each other and the adhesion of water molecules to other objects causing friction. • Cold water creates 2x as much friction as warm water. • An organism in warm water must be smaller than a same shaped organism in cold water to prevent sinking due to viscosity
Fish Senses • Sight – some fish can see color and can see in very dim light • Hearing – fish can hear • Smell – fish have nostrils used for smelling • Touch – fish can feel objects against their skin • Lateral line- A system of canals on the sides of fishes that helps fish detect changes in pressure, vibrations and currents
Lateral Line • Fish “hear” via their lateral lines, a line of pressure sensors running along each side of the fish that pick up pressure waves (= sound) in water. When someone pounds on an aquarium, that creates waves of pressure in the water that, to the fish, would be analogous to cupping your hands and pounding on your ears--NEVER POUND ON A FISH TANK!
Functions of the Lateral Line • Detect changes in pressure and vibrations and currents • Detect prey • Swim together in a school • Detect predators on the side or behind them • Pick up vibrations from the swimming together of other animals
BUOYANCY • Ways animals and plants avoid sinking • By adjusting body density to the same density as that of the water around them (neutral buoyancy). • Having flattened or bristly shapes that increase surface area and reduce sinking.