Marine Fishes
What is a fish??
Classic definition:
-Any of numerous cold-blooded aquatic vertebrates of the
superclass Pisces, characteristically having fins, gills, and a
streamlined body and including specifically, and...
-Any of the class Osteichthyes, having a bony skeleton, and...
-Any of the class Chondrichthyes, having a cartilaginous
skeleton and including the sharks, rays, and skates.
Although this is all accurate...we will find that fish are
considerably MORE!!
Fish similarities...
•
•
•
•
Vertebrate ( chordate)
Gills
Fins
Scales
What is a fusiform body shape?
•
•
•
•
pointed leading edge
maximum depth 1/3 body length back from head
posterior taper
caudal fin interrupts ideal fusiform shape
Hagfish (Agnatha): jawless fish
Lamprey
• Predatory/parasitic
• Rasping teeth
Parasitism of Great Lakes fishes…
Cartilagenous Fishes
(Sharks, Skates and Rays)
Distinguishing Traits
cartilaginous skeleton
no swim bladder
heterocercal tail
scales and teeth
spiracles present with 5-7 gill slits
males have claspers, internal fertilization
teeth in rows, are constantly replaced
Sharks exhibit extreme variability in size, shape and abilities.
Nearly 850 spp. of sharks, 350 exhibit typical
body morphology.
Variations on this theme are common.
Carchariniformes – basking sharks, filter feeder
Cetorhinus maximus
Mako
Isurus oxyrinchus
Great White
Lamniformes - mackerel,
mako, white sharks
-carnivores
Great White, Carcharodon carcharias
Skates and rays spend most of their lives near (on) the
ocean floor eating molluscs, squid, and small fish.
Yellow stingray, Urolophus jamaicensis
Like sharks, skates and rays come in
many shapes and sizes.
Blue spotted ray, Taeniura
lymma
Skates (order Rajiformes)
•pelvic fin divided into two lobes
•tail relatively stocky, no spine
Rays (order Myliobatiformes)
•each pelvic fin with one lobe
•tail relatively slender to whip-like spine
Boneless
vs.
Bony
Cycloid and Ctenoid Scales
Found in bony fishes (the Teleostei).
Overlapping = flexibility, over cosmoid
or ganoid scales.
Cycloid scales—smooth posterior margin.
(Greek "cyclo“ or circle.)
Fish form and function
show a high degree
of variation.
Coloration is also very
important in fish.
Here a stonefish “disappears”
amid the coral background.
Chromatophores, specialized
pigment cells within its
skin provide protective
coloration.
• Disrupt the outline of the fish
• Being dark on top, light on bottom
– Look like substrate from above
– Look like water surface from below
Warning coloration! May indicate poisonous amimal.
Fish Locomotion
• Primary forces involved in fish swimming:
– Thrust - force that propels forward
– Drag - friction produced from passing an object
through a medium
– Gravity – force from earth’s magnetic pull
(partially counterbalanced by density of water)
– Lift - upward force that counteracts gravity
Fish Feeding - function
• Herbivores
– < 5% of all bony
fishes, no
cartilaginous fishes
• browsers - selective eat only the plant
• grazers - less selective include sediments
• Detritivores
– 5 - 10% of all species
– feed on decomposing
organic matter
Fish Feeding - function, cont.
• Carnivores
– zooplanktivores
• suction feeding
• ram feeding
– benthic invertebrate
feeders
•
•
•
•
graspers
pickers
sorters
crushers
Fish Feeding - function, cont.
• Carnivores, cont.
– fish feeders
•
•
•
•
active pursuit
stalking
ambushing
luring
Fish feeding behavior
• Fish feeding behavior integrates morphology
with perception to obtain food:
– Search
– --> Detection
– --> Pursuit
–
--> Capture
–
--> Ingestion
Feeding behavior
• Fish show versatility in
prey choice and ingestion
• Behavior tightly linked to
morphology
(co-evolution)
Damselfish, Chromis spp.
Lateral line also aids in navigation in close quarters.
Predator avoidance
Migration for some salmon is a one-way trip!