Marine Fishes!

Did You Know?

There are more species of fish than of

all other vertebrates combined!

(~28,000)

Fish Classification

� Domain Eukarya

� Kingdom Animalia

�Phylum Chordata

�3 Classes:

�Agnatha

�Chondrichthyes

�Osteichthyes

Class Agnatha

� “Jawless” (no hinged jaw)

� Cartilaginous skeleton

� Eel-shaped; fin folds, no fins

� No scales

� Two groups:

� Lamprey: parasitic and non-

parasitic species

� Hagfish: scavengers, generally

considered disgusting (you’ll

see)

Lampreys

� Needle-sharp teeth

� Parasitic species can suck

30% of a fish’s blood in one

day

� Sea lamprey invasion of

Great Lakes

Hagfish

� Scavengers – eat dead or dying

fish from the inside out

� Produce lots of mucus (slime)

� Knot-tying

Class Chondrichthyes

� Cartilaginous skeleton

� Well-developed lower jaw

� Paired true fins

� Placoid scales (tooth-like)

� Spiracles (helps bottom-dwellers breathe)

� Three groups:

� Sharks

� Skates and Rays

� Chimaeras and Ratfish

Chondrichthyes Groups

� Sharks

� Skates and Rays

� Chimaeras and Ratfish

Class Osteichthyes

� Bony skeleton

� Hinged jaw

� Bony scales (4 main types)

� Swim bladder

� Lateral line

� Operculum

� There are more bony fish species than any other vertebrate

ctenoid

cosmoid

ganoid

cycloid

Two Living Osteichthyes Groups

� Lobe-finned Fish (Coelacanth and Lungfish)

� Ray-finned Fish (Everything else…)

Gills

� Very delicate, protected by the operculum

� Allow dissolved oxygen from the water to

diffuse into blood

Swim Bladder

� Can be filled with air

� Allows the fish to control its buoyancy (how

high it floats in the water)

Lateral Line

� Row of tiny pits, each containing a hair

� Senses changes in water pressure

� Allows fish to school

External Anatomy

Dorsal Fin

Lateral LineOperculum

Pectoral Fin

Pelvic Fin Anal Fin

Caudal Fin

Swimming Styles

� Accelerator

� Paddle-shaped caudal fin and

usually large mass at front of

body

� Quick and powerful

movement of caudal fin

causes rapid acceleration

� Cannot swim at high speeds

for long periods of time

� Ambush predators

Swimming Styles

� Cruiser

� Torpedo-shaped body

and crescent-shaped

caudal fin reduce drag

� Pectoral fins held fixed

like airplane wings

� Can sustain high

speeds for long periods

of time

� Open-ocean fish

� Top predators

Tuna: THE cruiser

Swimming Styles

� Maneuverer

� Pectoral fins are highly

mobile, allowing for great

maneuverability but little

speed

� Can swim easily amongst

coral and rocks and reach

into crevices to feed

� Body is typically flattened

into a vertical disc

� Reef fish