What is a Fish?

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Swimming Locomotion
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Major types of locomotion in fishes

• Walking
• frogfishes
• Crawling
• sea robins
• Swimming
• most fishes

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Antennariidae warty frogfish Antennarius maculatus

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The swimming mechanism

• Muscles
• Propulsive waves

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Swimming modes
Body musculature
Fin musculature
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Swimming modes (body musculature)
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Swimming modes
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Swimming examples
Thunniform Carangiform swimming Labriform
swimming
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Musculature myotomes
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Red
Epiaxial or dorsal muscles
hypaxial or ventral muscles
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Distribution of red muscle
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Distribution of red muscle
Bluefin tuna
Ectotherm fishes
Red muscle
Mako shark
Skipjack tuna
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• Propulsive wave
• Progressive tailward passage
• Push force
• Reactive force
• Forward thrust component
• Lift or slippage component

P
T
R
L
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Progressive swimming undulation wave
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Swimming Forces
Thrust - Drag Gravity - Lift Buoyancy
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Lift Force

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

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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

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Frictional Drag (Flow separation)
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Ctenoid scales
Placoid scales
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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

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Pressure and frictional drag
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High speed streamlined fishes
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Caudal keel
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Caudal fin shapes high aspect ratio (thunniform
swimming)
Scombridae Bigeye tuna Thunnus obesus
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Caudal fin shapes high/medium aspect ratio
(carangiform swimming)
Carangidae Jacks
Caranx melampygus
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Caudal fin shapes low aspect ratio
(subcarangiform swimming)
Serranidae Nassau grouper Epinephelus striatus
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Caudal fin shapes low aspect ratio
(subcarangiform swimming)
Esocidae Northern pike Esox lucius