Bony Fish

Class Osteichthyes  Includes all bony fishes  Cold-blooded vertebrates  Largest class of all vertebrates  Accounts for 96% of all fish species.  Freshwater and Marine

Distinguishing Features  Skeleton of bone  Scales  Paired fins  Single pair of gill openings  Jaws  Paired nostrils

Body Shape  Primarily Fusiform shape  Deviate in 3 ways  Laterally compressed: common for fish who live in dense cover or coral reefs. Example: Butterflyfish  Depressed: common in bottom dwelling fish Example: Sea Moth  Elongated: common in open ocean fish and eels. Example: Barracuda

Laterally Compressed  Butterfly fish

Depressed body shape  Sea Moth

Elongated  Barracuda

Coloration  Most fish species have pigmentation called chromatophores.  Chromatophores can contract and expand to change colors.  Iridescent- Reflective scales  Cave dwelling fish lack pigmentation.

Chromatophore  Fish using chromatophores to match background

Iridescent  Fish reflects light and matches background

Purpose of Coloration  Camouflage  Countershading  Disruptive coloration- breaks up animals shape  Change color to match surroundings  Advertisement to other fishes  Mate attraction and recognition  Territorial behavior  Warning signs

Disruptive Coloration  Moorish Idols

Bioluminescence  Some species produce light through a chemical reaction process.  Used to attract mates, confuse or deter predators, or attract prey  Light production occurs in  Photophores- light producing cells  Light-producing bacteria- live in or on the fish in a symbiotic relationship

Attract Prey  Angler Fish

Fins  Two kinds of fins-  Paired fins- Pectoral and Pelvic  Median fins- Dorsal, Caudal, and anal  Most fins are supported by rays (soft or rigid)  Some species have spiny rays associated with venom glands.  Example: Stonefish, Lionfish, Scorpionfish

Venomous Spines  Lionfish, warning colors

Head Structure  Mouth- located on anterior end  Nostrils- used for smell, no connection to mouth  Gills- Single pair of openings, covered by a flexible plate called Operculum.  Teeth- fused to the jaw bone  Eyes- size and position vary by habitat and behavior. Deeper = bigger eyes

Operculum

Scales  Scales are thin and flexible  Develop from bone tissue  Scales overlap from head to toe to reduce drag.  Covered by a thin layer of tissue as well as mucus.  Some bony fishes only have scales on portion of body, or none at all

4 Types of Scales  Cosmoid (primitive)  Ganoid  Cycloid  Ctenoid

Purpose of Mucus  Helps to protect fish from infection  Covers body to conceal scent from predators  Example: Parrotfish enclose their bodies in a mucus bubble at night so predators cannot detect them  Some juvenile fish feed on the mucus of parents

Parrotfish enclosed in Mucus

Buoyancy  Buoyancy provided by gas-filled swim bladder.  Gas volume changes as the fish changes depths.

Swim Bladder

Lifespan  Average lifespan of fish is years.  Larger species typically live longer than smaller species.  Infections and parasites are common causes of death in fish.

3 Types of fish Movement  1) Most fish swim with a rhythmic side to side motion of the body or caudal fin  2) Elongated fish like eels swim using a serpentine motion. They undulate their body in lateral waves that travel from head to tail.  3) Other fish, like tuna, have shorter bodies and swim by moving only powerful and rigid caudal tail. (fastest)

Reproduction  Most fish reproduce externally by spawning  Females lay eggs and males release sperm  Eggs will  1. Drift in water column  2. sink and remain on bottom  3. Eggs may be sticky and attach to plants etc.  4. Some fish brood eggs in mouth  5. Some bury eggs

Reproduction  Some fish have internal fertilization and are ovoviviparous.  Seahorse: Females deposit eggs in a pouch on the male’s abdomen.  The male then releases sperm and the eggs develop inside the male.  The male then gives birth  Some fish are hermaphrodites.  Sequential - Born one sex but change at some point during life due to social hierarchy/behavior  Synchronous- Have both sperm and egg producing organs at the same time.

Eggs  The number of offspring is inversely related to the chances of the eggs reaching maturity.  The larger number of eggs laid means there is a lower chance of surviving.  The Common Mola lays 28 million eggs in a single season.  The Atlantic Tarpon releases over 100 million every time it spawns.

Breeding Behavior  Various factors may influence breeding behavior.  1. Change in duration of sunlight  2. Temperature change of the water  3. Presence of the opposite sex  4. Change in currents, tide, or stages of the moon.

Breeding Cycles  Reproduction is generally cyclic in bony fish.  Some spawn many times a year, while others spawn only once a lifetime and then die soon after. Ex: Pacific Salmon  Anadromous- Fish that spend most of their time in the sea, but breed in rivers.  Catadromous- FW fish that migrate to the sea to breed.

Senses  Hearing- No external opening; inner ear for equilibrium, detecting acceleration, and hearing.  Eyesight- Well developed for some species.  Taste- taste buds inside mouth, responsible for accepting or rejecting prey  Smell- well developed  Lateral Line- Vibrations

Human Interaction  1. Commercial Fishing  2. Recreational fishing  3. Habitat destruction- building dams, stream diversion, destroy coastal wetlands  4. Pollution  5. Introduced species  6. Aquarium Collection