95% of all fish on Earth are bony fish. Bony Fishes 95% of all fish on Earth are bony fish. Bony fish have a vertebrae made of bone.

Cartilaginous Vs. Bony Fish Anatomy

Bony fish Respiration Gill Rakers-Prevent solid material from getting stuck in gills -Can be used for filter feeding Gill arch-structure to hold gills together; usually 4 Gill filaments: for gas exchange; contain capillaries

Operculum Cartilaginous fish do not have these; they have gill slits Bony fish have a hard bony covering that protects the gills inside.

How Gills work Counter current exchange of oxygen Oxygenated water flows in the opposite direction of blood through capillaries in the gill This allows for the greatest amount of oxygen to diffuse into the bloodstream of the fish

How Gills work Counter current exchange

Counter current exchange in motion

Bony fish have protective scales, which are loosely attached to the skin and overlap each other. Scales are covered with a slimy mucus produced by the skin to cover the scales. This mucus protects against infection and allows the fish to move more easily through the water.

Scales have bands called circuli that can tell the relative age of the fish, like growth bands of a clam shell.

Types of scales

Ganoid Scales Diamond Shaped Sturgeon

Ctenoid scales Perch Rounded with toothed edge

Cycloid Scales Circular Carp and Salmon

When more gas enters the bladder, the fish floats. Fish are buoyant because they have an internal gas filled organ called a swim bladder. When more gas enters the bladder, the fish floats.

Cartilaginous fish do not have a swim bladder. They have huge oily livers that increase their buoyancy.

Fish have a good sense of hearing. Sensitivity in Fish Fish have a good sense of hearing. They have an inner ear behind the brain, and sound receptors in tiny openings in the skin along each side of the body ( lateral line organ ).

Otolith Bone that fish use for hearing Grows in concentric rings Can figure out the age of the fish by counting rings (like a tree stump)

Fish can smell, and have a pair of nostrils or nares. Fish have good vision. Fish in clear surface waters have better color vision than those that live deeper.

Most fish have external fertilization and development. Reproduction in Fish Most fish have external fertilization and development. Gametes ( sperm and egg ) are released in a process called spawning.

Unusual Adaptations in Fish The puffer fish and porcupine fish can inflate their stomach with water when threatened, resulting in a balloon shaped body. When they do this, sharp spines on the skin stick outward.

Flatfish such as the flounder and fluke can use camouflage to match their surroundings due to special pigments in their cells. Flatfish also have both eyes on one side of the body ( for better vision when lying flat on the sand ). When born, the eyes are on different sides but they migrate over time to end up together.

The sea horse is a fish that transfers fertilized eggs from the female to the male where they develop in the brood pouch on the abdomen of the male’s body.

The flying fish has the ability to swim fast and expand its wing like pectoral fins to allow it to fly about 100 meters, more than 10 meters above the water’s surface.

They use this light to attract mates, or as a lure to catch prey. Some deep sea fish have the ability to produce light in their bodies called bioluminescence. They use this light to attract mates, or as a lure to catch prey.