1. Common Characteristics
2. Diversity
3. Classification
4. Form and Function
5. Fins and Function
6. Sensation

Fishes

1. Ectothermic
2. Limbless
3. Fins
4. Many have scales of enamel-like material

Marine Versus Freshwater Fishes

1. 42 percent of all fish species live in freshwater
2. 58 percent of all fish species are marine

Nearshore Fishes

1. 46 percent of all species live in shallow, nearshore waters
2. 40 percent in shallow warm waters
3. 6 percent in shallow cold waters

Offshore Fishes

1. 12 percent of all species live in the waters of the open ocean
2. 1 percent in the surface waters
3. 5 percent in the deep waters
4. 6 percent associated with the bottom

Three Fish Classes

1. Agnatha
2. Chondrichthyes
3. Osteichthyes

Jawless Fishes

1. Class Agnatha
2. Hagfish and lamprey
3. Remnants of an ancient group

Characteristics of Agnatha

1. Skeleton of cartilage
2. No jaws
3. No scales
4. No operculum
5. No swim bladder

Cartilaginous Fishes

1. Class Chondrichthyes
2. Sharks, skates and rays

Characteristics of Chondrichthyes

1. Skeleton of cartilage
2. Teeth not fused to jaw
3. Scales placoid
4. Nostrils located ventrally
5. No operculum
6. No swim bladder
7. Osmoregulation: High blood urea concentrations

Bony Fishes

1. Class Osteichthyes
2. Perch, bass, salmon, eels, scorpionfish & many others

Characteristics of Osteichthyes

1. Skeleton of bone
2. Teeth fused to jaw
3. Scales ctenoid or cycloid
4. Nostrils located dorsally
5. Operculum present
6. Most have swim bladder
7. Osmoregulation: Drink water and gills remove salt

Body and Swimming

1. Fish swim with a side-to-side (sinusoidal) motion of body
2. Alternate contractions of V-shaped myomeres on each side of spine produce motion

Body Shapes

1. Fusiform
2. Compressed
3. Depressed
4. Attenuated

Body Shape and Swimming Efficiency

1. Overall body shape affects swimming efficiency
2. The passage of the fish's body through the water produces turbulence on its surface, creating drag, and drag slows the fish down

Fusiform

1. Torpedo-shaped
2. Streamlined
3. Little turbulence
4. Can attain fast speeds (6-60 mph)
5. Swordfish, 60 mph

Compressed, Depressed, or Attenuated

1. Less streamlined
2. More turbulence
3. Slower swimming speeds (1-5 mph)
4. Eel, 2.6 mph

Fins and Swimming

1. Fin movements are brought about by muscles attached to the base of the fins and by the movement of the body as a whole
2. Fins are involved in maneuvering and in producing thrust
3. Fins also produce drag

Paired Fins

1. Pectorals are lateral just behind gill slit(s)
2. Pelvics are ventral, often behind pectorals
3. Turning, balancing, and braking
4. Pectorals provide lift in sharks

Unpaired Fins

1. Dorsal is located on back; has 1, 2, or 3 parts with spiny and soft portions in bony fishes
2. Anal (Ventral) is located below and posterior to the anus; has 1 or 2 parts with spiny and soft portions in bony fishes
3. Prevent rolling

Caudal (Tail)

1. Soft
2. Attached by peduncle
3. Provides thrust

Heterocercal Tails

1. One lobe longer than the other
2. Sharks and sturgeons
3. Provides lift as well as thrust

Homocercal Tails

1. Two lobes of equal size
2. Most bony fishes
3. Provides thrust but not lift

Homocercal Tail Shapes

1. Round as in groupers, filefish, and gobies
2. Truncate as in barracuda, snappers, and grunts
3. Forked as in tarpon, bonefish, and damselfish
4. Lunate as in tuna, makerel, and jacks

Tail Area and Swimming Efficiency

1. Large surface area develops more thrust but increases frictional drag
2. Small surface area develops less thrust but reduces frictional drag

Aspect Ratio (AR)

1. A measure of swimming efficiency
2. AR = [(fin height)²] / [fin area]
3. Ranked on a scale of 1 to 10

Tail Shape and Swimming Efficiency

1. The higher the aspect ratio, the greater the swimming efficiency
2. The lower the aspect ratio, the greater the maneuverability

Rounded Tails

1. Low aspect ratio (1)
2. Groupers, filefish, and gobies
3. A lot of drag
4. Good for accelerating and maneuvering
5. Poor for fast sustained swimming

Truncate and Forked Tails

1. Intermediate aspect ratios (3-5)
2. Barracuda, snappers, grunts, tarpon, bonefish, and damselfish
3. Less drag
4. Less maneuverable
5. Better for fast sustained swimming

Lunate Tails

1. High aspect ratio (7-10)
2. Tuna, makerel, and jacks
3. Very little drag
4. Poor for maneuvering
5. Excellent for fast, sustained swimming

Atypical Swimming

1. Fins other than the caudal used for thrust
2. Dorsal and anal fins of triggerfish and ocean sunfish
3. Pectoral fins of pufferfish and wrasses

Senses

1. Sight
2. Smell
3. Taste
4. Electroperception
5. Hearing
6. Balance

Sight

1. Adaptations for underwater vision:
2. Lenses are hard, dense, and round to refract light
3. Lenses are moved by muscles to focus light on the retina

Smell

1. Olfactory sacs connected to nostrils
2. Nostrils have external incurrent and excurrent openings

Taste

1. Taste buds located in pits
2. Located on exposed surfaces of mouth, lips, skin, barbels and fins

Electroperception

1. Detect weak electric currents
2. Can detect the earth's magnetic field (built in compass)
3. Ampullae of Lorenzini in sharks

Hearing

1. No outer ear
2. Inner ear canals lined with sensory hairs
3. Lateral line detects low frequency vibrations
4. Swim bladders amplify sounds (can help to produce sounds)

Balance

1. Otoliths (ear stones) located in inner ear
2. Sensory cells detect movements of otoliths and determine position