Fish Morphology The morphology of a fish is a result of adaptations to several forces. Environmental influences cause variations in the general structure of a fish.

Pectoral and Pelvic Fins Pectoral and pelvic fins are paired fins. Main function: Turning

Dorsal and Anal Fins Main Function: Balance, Prevent pitching and spinning

Caudal Fin The caudal fin is a life-style indicator The aspect ratio of the caudal fin of a species closely correlates with its average level of activity (Pauly 1989).

The Aspect ratio (A) of the caudal fin is calculated from: The Aspect ratio (A) of the caudal fin is calculated from: A = h2 / s where h is the height of the caudal fin and s its surface area High apsect ratio, like this lunate, is efficient high speed =Cruiser Low aspect ratio, like this rounded, is good for short bursts of speed.

High aspect ratios Low aspect ratios small surface area move less water go faster for longer periods of time think speed boat propeller Low aspect ratios large surface area move more water use more energy cannot swim long think paddle boat propeller

Heterocercal Caudal Fin asymmetrical characteristic of sharks produces lift in addition to thrust.

Body Shape An adaptation to 3 types of drag (resistance) Frictional drag – due to skin touching water ideal shape = sphere Form Drag – due to the amount of water that must be displaced as the fish is moving forward ideal shape = thin cylinder Turbulence – uneven pressure due to water traveling around the body ideal shape = streamline (length is 4.5 > diameter)

Frictional drag due to skin touching water ideal shape = sphere

Form Drag due to the amount of water that must be displaced as the fish is moving forward (think of a big-rig truck pushing through the wind) ideal shape = thin cylinder

Turbulence uneven pressure due to water traveling around the body ideal shape = streamline (length is 4.5 > diameter)

Fusiform Combined adaptations for the 3 types of drag

Body Form and Function Body Form varies according to lifestyle Cruising specialists tend to have a fusiform shape

Body Form and Function Maneuvering specialists tend to have a tall and elliptical shape. Good for precise/sharp turns

Body Form and Function Accelerating specialists tend to have thinner longer bodies.

Other Forms and functions Elongated body moved slowly conserves energy Examples: Gulper Eel and Bristle-mouth Fish live in the mesopelagic

Flat Fish Flat Body allows them to sit on sea floor examples: Flounder, Halibut, Rays...

Finlets Help to decrease/control turbulence of water riding over dorsal and anal fins Found on fast cruisers (tuna, sailfish...)

Deep Sea Fish Eye Adaptations Large eyes to see better (or they are completely blind or have small eyes in areas where there is absolutely no light) Eyes pointed upward – most of the food is coming/sinking from above

Deep Sea Fish Mouth and Feeding Adaptations Large mouth – enables it to take in prey that is as large or larger than itself Large pointed teeth – enables them to grab/kill most if not all prey Small – not a lot of food to support a large body Distensible gut - gut stretches to swallow food as large or larger than them

Deep Sea Fish Body Adaptations Gelatinous skeleton – to deal with the pressure Muscle soft – to deal with the pressure Long body – allows for slow propulsion (conserves energy) Small fins – don’t do much turning

Deep Sea Fish Bioluminescence Adaptations Many have photophores (light organs) Attract prey Startle/confuse predators Attract mates