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Class: Osteichthyes - Bony Fish

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.

Marlin Photo by Betty Newton

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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

Tuna, barracuda and a few others maintain temperature higher (~10o) than environment so technically they are endothermic.

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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

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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.

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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.

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Reproduction: sexual, mostly external fertilization called spawning

Gonads - sac contains either sperm or eggs (roe).

Sex reversal is common in reef fish

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The red blood cell count in tuna is equal to mammals.

Bluefin tuna and sailfish are the fastest fish at nearly at 70 mph.

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Tuna are exquisitely designed for speed and can swim at 45 mph for long periods.

They have a foldable dorsal fin that fits into a groove making it flush with the body to reduce drag when maneuvering.

NOAA

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The largest bony fish is the Mola Mola (Sunfish).

Molas eat plankton and can weigh 3000 pounds. They swim slowly and do not have a fusiform body shape, although it can be 11 ft. long.

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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