1. Class: Osteichthyes - Bony Fish
Marlin Photo
by Betty Newton
As Chordates, fish have an incredible variety of characteristics.
Most are covered with flat scales that fit into pockets in the skin and have a mucus coating.
Some lack scales or have tiny scales.
Some can be reabsorbed if food is scarce.
Scales contain chromatophores that cause color changes for camouflage, mating - species recognition or when stressed.

2. false eye
Cryptic coloration: false eye on butterfly fish;
counter-shading, (dark on dorsal surface and light on ventral);
Camouflage (aid in survival)
Circulation: 2 chambered heart, most ectothermic (cold-blooded)
Tuna, barracuda and a few others maintain temperature higher (~10o) than environment so technically they are endothermic.

3. Gills help regulate the salt/water balance called osmoregulation.
Respiration: Water containing 02 flows over the gills in a different direction than blood so diffusion is maximized; muscles pump water through gills
Gases from the blood and/or gulped air are used to adjust buoyancy in the swim bladder.
Several gill arches supporting gill rakers and gill filaments are covered by a flap called the operculum.
Gills help regulate the salt/water balance called osmoregulation.
NOAA

5. CROSS SECTION - variable
FINS – flexible and moveable

6. Vision: Poor to medium and usually only lateral.
Some fish can detect and generate weak electrical currents.
This electro-perception is used to communicate in schooling, aids in migration, detecting and stunning prey.

7. Hearing: Aided by the lateral line, the swim bladder and the otoliths (located in the inner ear) detect movements and affect balance.
Smell: Chemoreceptors are found on the mouth, lips, skin and fins.
Most of brain is olfactory lobes use for smell to find food.

8. Reproduction: sexual, mostly external fertilization called spawning
Gonads - sac contains either sperm or eggs (roe).
Sex reversal is common in reef fish

9. The red blood cell count in tuna is equal to mammals.
Bluefin tuna and sailfish are the fastest fish at nearly at 70 mph.

10. Tuna are exquisitely designed for speed and can swim at 45 mph for long periods.
NOAA
They have a foldable dorsal fin that fits into a groove making it flush with the body to reduce drag when maneuvering.

11. The largest bony fish is the Mola Mola (Sunfish).
Molas eat plankton and can weigh pounds. They swim slowly and do not have a fusiform body shape, although it can be 11 ft. long.

12. HUMAN IMPACTS
Overfishing – results when catches are higher than the maximum sustainable yield, or optimal catch, of a fishery
- with time catches dwindle, fish caught are smaller
For a sustainable yield, the number of fish caught must be no more than the number of new fish added through reproduction