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

Photic Zones in the Ocean

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? 2 nd 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.

Barracuda

Types of Fins 1.Tail Fin (CAUDAL FIN) 2.Paired Fins (PECTORAL and PELVIC FINS) 3.Medial Fins (DORSA and ANAL FINS)

External Anatomy of a Fish

External Anatomy

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.

How a Fish Swims

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 Fins Dorsal 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

Caudal Fins Push the fish forward

Aspect Ratio and Fin Types

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.)

Measuring Length

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

Salmon

Salmon Red Muscle

Yellowfin Tuna

Barracuda

Flounder

Flounder 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

Water 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

Fish Eyes

Fish Hearing

Fish Smell

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 1.By adjusting body density to the same density as that of the water around them (neutral buoyancy). 2. Having flattened or bristly shapes that increase surface area and reduce sinking.

Maintaining Buoyancy To maintain buoyancy the fish will either: –Adjust the density of its body by using a SWIM BLADDER –They will adjust the density of the components of their insides (they will consume lighter weight ions and leave the heavier ones in the surrounding water)

SWIM BLADDERS A swim bladder is a balloon-like structure that is: – inflated to make the fish rise higher in the water –or deflated to make the fish sink lower

SWIM BLADDER

CLOSEDOPEN

No Swim Bladder Some fish like Tuna do not have a swim bladder and must swim fast to prevent sinking Some fish like catfish do not have a swim bladder and spend their life on the bottom

Respiration Fish use gills to absorb oxygen from the surrounding water

Comparison of Gas in Ocean Water and the Atmosphere Undissolved Gas Chemical SymbolPercentage in AirPercentage in Sea Water NitrogenN OxygenO Carbon DioxideCO Dissolved Oxygen

Dissolved Gases GasOceanAtmosphere Oxygen5-10ml/L200ml/L Dissolved gases vary in water with temperature and salinity. Cold fresh water can hold more dissolved gas than warm saltwater.

Parts of a Gill Gill Arch - stiff structure that supports the gill filaments and the gill rakers Gill Rakers – prevent food from clogging up the gill filaments Gill Filaments – fingerlike projections where oxygen is absorbed and carbon dioxide is removed

Parts of a Gill

Fish Breathing

How Fish Breathe

Counter-Current System Gas is exchanged in gills because water and blood move along side each other in opposite directions

PRESSURE AND DEPTH A column of water only 10 m deep exerts a pressure of 1 ATM. Every 10 m of water exerts another ATM of pressure. Organisms living at 100m or 500m are subjected to 10 ATM or 50 ATM (plus 1 ATM of air pressure above the sea).

PRESSURE AND DEPTH

Fish and Body Temperature Types of temperature systems –Endothermic (homeothermic) maintain a constant internal body temperature (ex. Humans F) –Ectothermic or Poikilothermic - have a temperature similar to their surroundings (ex. If the water is 56 0 F F then the fish will have a body temperature around 56 0 F)

Fish Reproduction Most fish have internal sex organs that we cannot see. fish gonads (sex organs) produce gametes (sex cells) only at certain times. These times must be the same for both males and females and must be timed to the most favorable conditions.

Fish Reproduction Fish may only reproduce when there: 1. Is enough of the right kind of food 2.There are enough hours of light each day 3. The water is the right temperature

Fish Reproduction Includes: –Courtship: a series of behaviors designed to attract mates –Spawning: a release of gametes into the water –Copulation: a direct transfer of sperm into a females body

Fish Reproduction Most fish reproduce by spawning. –This is when the female swims and lays eggs on plants or sand in the water –The male fish swims behind her depositing sperm into the water where some of it may land on and fertilize the eggs

Sunfish Spawning

Fish Reproduction Other Fish give birth to live young like humans (ex. Guppy giving birth)

Fish Reproduction –Some fishes are hermaphrodites. They have both male and female gonads –Hermaphrodism is more common among the deep-water fishes. (Gourami)

Deep Sea Fish Deep Sea Fangtooth

Fish Reproduction Reproduction in fishes involves many adaptations that help individuals get together and select mates.

Fish Courtship Mandarin Fish Dancing to attract a female

Fish Reproduction Sex Reversal –Males may change to females or females to males (ex. Clownfish)

Sex Reversal Among some species of anemone fishes a single large female who mates only with a single large dominant male inhabits each sea anemone. All others are small non-breeding males. If the female disappears her mate changes into a female and the largest of the non-breeding males becomes the new dominant male. The new female can start spawning as soon as 26 days after her sex change.