Swimming Locomotion Major types of locomotion in fishes

Swimming & Locomotion

Major types of locomotion in fishes • Walking – frogfishes • Crawling – sea robins • Swimming – most fishes

Antennariidae warty frogfish Antennarius maculatus

The swimming mechanism • Muscles • Propulsive waves

Swimming modes Body musculature Fin musculature

Swimming modes (body musculature)

Swimming modes

Swimming examples Thunniform – Carangiform swimming Labriform swimming

Musculature myotomes

Red Epiaxial or dorsal muscles hypaxial or ventral muscles

Distribution of red muscle

Distribution of red muscle Ectotherm fishes Skipjack tuna Red muscle Bluefin tuna Mako shark

Propulsive wave • Progressive tailward passage • Push force • Reactive force • Forward thrust component • Lift or slippage component P T R L

Progressive swimming undulation wave

Swimming Forces Thrust - Drag Gravity - Lift + Buoyancy

Lift Force • Static lift – Swim bladder – Lipids / Oils • Dynamic Lift – Pectoral fin rotation – Pectoral hydrofoil shape

Drag forces I • Frictional or Viscous Drag – Boundary layer: non-moving water layer that creates friction with surrounding water – Not speed related – To reduce frictional drag: • • Mucous Reduction surface area Ctenoid scales Placoid scales

Frictional Drag (Flow separation)

Ctenoid scales Placoid scales

Drag forces II • Pressure or Inertial Drag – Caused by pressure differences – Drag increases with speed – To reduce pressure drag: • Streamline shape – – Width-length ratio = 0. 25 Thickest cross-section 2/5 from mouth Long and narrow wing-like pectoral fins for lift Body depressions for retracting paired & median fins

Pressure and frictional drag

High speed streamlined fishes

Caudal keel

Caudal fin shapes high aspect ratio (thunniform swimming) Scombridae Bigeye tuna Thunnus obesus

Caudal fin shapes high/medium aspect ratio (carangiform swimming) Carangidae Jacks Caranx melampygus

Caudal fin shapes low aspect ratio (subcarangiform swimming) Serranidae Nassau grouper Epinephelus striatus

Caudal fin shapes low aspect ratio (subcarangiform swimming) Esocidae Northern pike Esox lucius