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