Osteichthyes: Bony Fish

About 23,000 different species

AKA: Teleosts

Diversity of fishes

Dorsal

Anatomical terminology

Ventral

Posterior or caudal

Anterior Lateral Lateral

Used for relating different parts….Eye is posterior to the mouth

Conversely the mouth is anterior to the eye

External Anatomy

Sail fish (Istiophorus platypterus)

American eel (Anguilla rostrata)

Fins Mouth Scales

White sucker (Catostomus commersonii)

River hatchetfish (Gasteropelecus sternicla )

Longnose gar (Lepisosteus osseus)

Great white shark (Carcharodon carcharias)

Spines vs. rays

Bluegill

(Lepomis macrochirus)

Spines • Rigid

• Often for defense

Rays • Flexible

• Often branched

• Mainly for support

Fisheries ecologists use both spines & rays for identification and aging!

Mouth placement

superior terminal

Inferior (sub-terminal)

Fins Dorsal

Anal

Pelvic

Pectoral

Adipose

Pectoral Pelvic

Caudal

Anal

Heterocercal • Tip of vertebral column turns upward

• Epicercal: dorsal lobe larger (sturgeon)

• Hypocercal: ventral lobe longer (flying fish)

Protocercal

• Extends around vertebral column

• Embryonic fish; hagfish

Homocercal • Vertebral column stops short of caudal fin,

which is supported by bony rays

• Symmetrical

Diphycercal • 3 lobed; lungfish and coelacanth

• Vertebral column extends to end of caudal fin, dividing into symmetrical parts

Scale types

• Placoid

• Ganoid

• Cycloid

• Ctenoid

Placoid: sharks and

rays

decrease drag.

Ganoid: bowfin, paddlefish, gar, sturgeon

Armor-like plates for protection

Cycloid and Ctenoid: most bony fishes (teleosts) • Overlapping = Flexibility, reduced drag

• Both grow in concentric rings Cycloid: smooth outer edge, soft-rayed

fish (e.g., salmon)

Ctenoid: “toothed” outer edge, spiny fish (e.g., bass)

Body Shape

• Related to lifestyle

• Fusiform (streamlined body)-helps move through water easy, fast swimmer

-Ex: Sharks, Tuna, Marlins

Body Shape Cont’d

• Laterally Compressed- leisurely swimming around coral/kelp

-Ex: Angelfish, damselfish, butterfly fish

• Elongated body- live in narrow spaces -Ex: moray eels, trumpet fish, pipefish • Round- porcupine fish

• Flatfish- actually laterally compressed. Adapted to live on bottom

• Lie on side, both eyes on top

– (born w/ eyes on each side)

FLOUNDER SOLE

HALIBUT

• Dorsoventrally flattened- demersal fish

-Ex: Rays, skates

Trumpet Fish

Stonefish Blennies

Coloration

LIONFISH

CRYPTIC

WARNING

DISRUPTIVE

COUNTER SHADING

Locomotion • Rhythmic side to side motion

• swim bladder for buoyancy and lift

-pectoral fins used to hover and swim backwards

Fish Circulation

• Fish heart has 2 chambers

• Single loop circulation

• Blood flows into gills, picks up O2, goes

to the body, returns to the heart.

Gills

• Gills are the main

site of gas exchange

in almost all fishes.

• The gills consist of bony or

stiffened arches (cartilage) that

anchor pairs of gill filaments.

Numerous lamellae protrude from both sides of each filament and are the primary sites of gas exchange.

Microscopic gill structure: showing gill filament and lamellae (Red blood cells

evident.)

Lots of surface area…Oxygen diffuses right into blood stream!

• Water flows over gills as fish opens mouth.

• Water flows OPPOSITE direction of blood flow

(countercurrent system)

Higher conc. of O2 in water than in blood…O2 diffuses from the

water into the blood.

WHAT WOULD HAPPEN IF THEY FLOWED IN SAME

DIRECTION? (Co-Current)?????

COUNTER-CURRENT

Water

Blood

Water

Blood

So, they efficiently extract oxygen by….

• Short diffusion distance at gill site

• Large surface area for diffusion at gill site

• Counter current exchange of gases at gill site

• Large volume of water passes over gills

Why school? • Protects against predation

• Causes confusion, encircle a predator

• Hard to pick out one

• Maybe… swimming efficiency (fish in front reduces water resistance)

Hermaphrodites • Some marine hamlet fish are

hermaphrodites

– Although they could fertilize own eggs, they still cross fertilize

• Found in many deep sea fish when mates are hard to find

Sex Reversal • Most prevalent in some sea basses, grouper,

parrotfish, wrasses, clown

• male female (protandry)

female male (protogyny)

• controlled by sex hormones but triggered by social cues – i.e.: absence of dominant female in

hierarchy

Fishing Methods

REDUCING BYCATCH

• Dolphins and tuna known to swim together and caught in purse seines

– Backdown method for “dolphin safe tuna”

• Turtles often caught in trawlers

– Turtle Excluder Devices (TED)

Overfishing

• Growing world population

• Large scale fishing methods

• Improved technology

• Competition for profit

• No recovery time

• Depletion of natural populations

Aquaculture (fish farms)

• Marine aquaculture refers to the culturing of species that live in the ocean. U.S. marine aquaculture primarily produces oysters, clams, mussels, shrimp, and salmon. Marine aquaculture can take place in the ocean (that is, in cages, on the seafloor, or suspended in the water column) or in on-land, manmade systems such as ponds or tanks. Recirculating aquaculture systems that reduce, reuse, and recycle water and waste can support some marine species.

• Freshwater aquaculture produces species that are native to rivers, lakes, and streams. U.S. freshwater aquaculture is dominated by catfish but also produces trout, tilapia, and bass. Freshwater aquaculture takes place primarily in ponds and in on-land, manmade systems such as recirculating aquaculture systems.

-NOAA