fish swim
TRANSCRIPT
Contents
Fins How fish swim Forces acting on swimming fish Types of swimming and their modes How fish generates lift Forces resisting movement
Fins/ Propulsors• Provide control over movements by directing thrust, supplying lift and even acting as brakes.
• A fish must control its pitch, yaw, and roll. 1. Caudal fins – provides thrust and control direction2. Pectorals – acts as rudder, steer up or down, also helps in
stop.3. Pelvics – mostly control pitch4. Dorsal fin – control roll 5. Anal fin – stabilizing
How fish swim
• A fish swims by contracting and relaxing
complex network of muscles blocks along
the sides of its body, known as ‘Myomeres ’.
• Creates a series of waves travelling down
the fish body.
• The rear part of each wave thrusts against
the water and propels the fish forward.
Forces acting on a swimming fish
• Part of fish pushing against water (side or tail creates normal force (reactive) pushing in opposite direction.
• Normal force has two components:- Thrust – It pushes fish forward. Lift -- It pushes to side.All lift forces cancels out over one
complete tail stroke.
Myomeres
Function :- make body undulate• Causes body to bend because myomeres on one
side contract, while other member of pair on other side relaxes.
• Seprated by connective tissue, mysopeta that connect to vertebrae. — myomeres shaped like sideways “W” - middle connects forward, sides to back.
— one myomere per vertebra
Types of swimmingA. Body and Caudal Fin swimming (BCF). 1. undulation 2. oscillation
B. Median and Paired Fin swimming (MPF). 1. undulation 2. oscillation 3. rowing/sculling
Undulation :- wavelength pass down length of body.Oscillation :- structure (fins) pivots on a base.
Body and Caudal fin swimming (BCF)
• Most common “fishy swimming”.• A wave of muscular contraction from head to tail. - swings tail back and forth. - strength & amplitude of contraction increases
toward tail.• Different fish swim by undulating different parts of
their bodies.
ANGUILLIFORM CARANGIFORM OSTRACIFORM
-body flexes one full - These swimmers undulate the - Body rigid, tail oscillates wavelength, with head acts posterior half of their body . as fulcrum. Body flexes < 1 wavelength -Typically slow swimmers - much faster than anguilliform - relatively slow swimmers swimmersIt is usually seen in fish with Tuna Boxfish long slender bodies like white sharks Torpedo rays Eel salmon momyrs Lampreys jack fish and maco sharks.Many varieties of larvae and oar fish.
Swimming modes of BCF Propulsion
Median and paired fin swimming
• Rowing (sculling) :- - It is same as oars... - power stroke with fin expanded - return stroke with fin collapsed• Oscillation :- - pectoral fins oscillated slowly or rapidly (like a bird) - generates lift - requires large mass in pectoral girdle• Undulation :- - usually median fins (dorsal and anal) - sinusoidal waves run down fins - can also undulate pectoral fins (skates, puffers)
Swimming modes of MPF Propulsion• Rajiform :- Thrust generation involves the passing of vertical undulations along the
pectorals that are very large, triangular shaped, and flexible. The fins may also be flapped up and down.
- likened to the flight of birds. Eg:- rays, skates and mantas• Diodontiform :- propulsion is achieved by passing undulations down broad pectoral
fins. - Up to two full wavelengths may be visible across the fins. Eg:- puffer fish• Amiiform :- swimming is by undulations of a (usually long-based) dorsal fin, while
the body axis is in many cases held straight when swimming. eg:- african fresh water eel• Gymnotiform :- since propulsion is obtained by undulations of a long-based anal
fin. - dorsal fin is usually absent Eg:- knife fish• Balistiform :- both the anal and dorsal fins undulate to generate the propulsion
forces. - their median fins are usually inclined relative to each other, while the body
is usually flat and compressed laterally. eg:- trigger fish
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How fish generate lift• The swim bladder acts just like a
balloon – with the ability to control the amount of gas.
• More gas is added to the swim bladder to move to a higher level in the water.
• Gas is released from the swim bladder to move to a lower position in the water.
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Inflating the Swim Bladder
• Inflating the swim bladder is an active process that generally involves a gas gland.
• The gas gland is rich with capillaries and acts to concentrate oxygen until the pressure of oxygen in these capillaries is greater than in the swim bladder.
• Oxygen will then diffuse from capillaries associated with the gas gland into the swim bladder, causing it to inflate, and allowing the fish to rise.
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Deflating the Swim Bladder• The primary gas in a swim bladder
is oxygen. To maintain a lower position, the swim bladder must release some of the oxygen.
• Deflating the swim bladder is a passive process. Higher pressures inside the swim bladder force oxygen to diffuse into the blood stream in surrounding capillaries.
• This allows the fish to sink to a lower depth.
O2
O2
O2
High Pressure
O2 O2
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Drag Forces
• Frictional drag: caused by water molecules sticking to skin
• proportional to: (surface area of body) x (velocity)
• minimize surface area (be a sphere)• The slime coat provides a smooth
surface that allows laminar flow and minimizes frictional drag.
Figure from http://www.geocities.com/aquarium_fish/how_fish_swim.htm
Pressure drag : Caused by pressure differential between front and back of fish• minimize by...-- improving streamlining (fusiform shape, fin slots)-- directing flow (caudal keels, finlets, scales)
Form drag: caused by displacement of water• proportional to:(cross-sectional area of body) x (velocity2)• minimize by being slender
Different types of swimmers
Maneuvers
(butterfly fishes, damselfishes, angelfishes)
- slow moving, so drag & inertia relatively
unimportant
- deep, compressed bodies that can be
turned quickly
MPF rowing/sculling
Accelerators
(barracuda, pike, giant sea bass, groupers
- need to overcome inertia, drag less
important
maximize thrust by having large surface area in rear of body
Generates thrust by BCF undulation
Cruisers
(tunas, mackerels, marlins, jacks)
Low form and friction drag due to
streamlined & smooth body
Higher acceleration
Generate thrust by BCF undulation
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REFERENCES
– http://www.amonline.net.au/FISHES/students/dissect/swimbladder.htm
– http://lookd.com/fish/swimming.html– http://www.fisheriesmanagement.co.uk/index.htm– http://www.scienceandthesea.org/index.php?
option=com_frontpage&Itemid=1– http://lookd.com/fish/index.html– https://www.tpwd.state.tx.us/– https://googleimages.com