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How Do Fish Swim?How Do Fish Swim?

A Presentation for The Angelfish SocietyA Presentation for The Angelfish Societyby Tamar Stephensby Tamar Stephens

For the April 22, 2007 General Members For the April 22, 2007 General Members MeetingMeeting

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To be able to swim, fish need to:To be able to swim, fish need to:

Overcome dragOvercome drag

Maintain their vertical position in the Maintain their vertical position in the water columnwater column

Maintain an upright positionMaintain an upright position

Change directionsChange directions

Move efficientlyMove efficiently

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This presentation gives an This presentation gives an overview of the roles of: overview of the roles of:

Slime coatSlime coat

Body shapeBody shape

Swim bladderSwim bladder

FinsFins

Skeletal SystemSkeletal System

MusculatureMusculature

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Overcoming DragOvercoming Drag

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Imagine wading through water…Imagine wading through water…

The first thing you notice is that The first thing you notice is that you have to push hard against you have to push hard against the water to move forward.the water to move forward.

The faster you go, the harder The faster you go, the harder you have to push.you have to push.

With each step you have to With each step you have to overcome drag. overcome drag.

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Drag ForcesDrag Forces

Pressure drag is the force Pressure drag is the force needed to push water out of the needed to push water out of the way to swim forward. way to swim forward.

Frictional drag can cause Frictional drag can cause turbulence, making it harder for turbulence, making it harder for water to flow smoothly across water to flow smoothly across an object.an object.

An angelfish’s An angelfish’s streamlined streamlined body shapebody shape reduces reduces pressure drag.pressure drag.

The The slime coatslime coat provides a provides a smooth surface that allows smooth surface that allows laminar flow and minimizes laminar flow and minimizes frictional drag. frictional drag.

   

Figure from http://www.geocities.com/aquarium_fish/how_fish_swim.htm

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Maintaining Vertical PositionMaintaining Vertical Position

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Neutral BuoyancyNeutral Buoyancy

If you have raised angelfish, you have almost If you have raised angelfish, you have almost certainly seen little belly sliders that have to work certainly seen little belly sliders that have to work hard to swim upward to feed.hard to swim upward to feed.

Maybe you have seen fry or small juveniles that Maybe you have seen fry or small juveniles that have over-inflated swim bladders and have to have over-inflated swim bladders and have to work hard to swim downward to keep from work hard to swim downward to keep from floating on the surface.floating on the surface.

It takes less energy to be neutrally buoyant, so It takes less energy to be neutrally buoyant, so the angelfish neither bobs to the surface or sinks.the angelfish neither bobs to the surface or sinks.

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The Swim Bladder maintains The Swim Bladder maintains neutral buoyancyneutral buoyancy

The The swim bladderswim bladder acts just like acts just like a balloon – with the ability to a balloon – with the ability to control the amount of gas.control the amount of gas.

More gas is added to the swim More gas is added to the swim bladder to move to a higher level bladder to move to a higher level in the water.in the water.

Gas is released from the swim Gas is released from the swim bladder to move to a lower bladder to move to a lower position in the water.position in the water.

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Deflating the Swim BladderDeflating the Swim Bladder The primary gas in a swim The primary gas in a swim

bladder of angelfish is oxygen. bladder of angelfish is oxygen. To maintain a lower position, the To maintain a lower position, the swim bladder must release some swim bladder must release some of the oxygen.of the oxygen.

Deflating the swim bladder is a Deflating the swim bladder is a passive process. Higher passive process. Higher pressures inside the swim pressures inside the swim bladder force oxygen to diffuse bladder force oxygen to diffuse into the blood stream in into the blood stream in surrounding capillaries. surrounding capillaries.

This allows the fish to sink to a This allows the fish to sink to a lower depth.lower depth.

O2

O2

O2

High Pressure

O2 O2

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Inflating the Swim BladderInflating the Swim Bladder

Inflating the swim bladder is an active Inflating the swim bladder is an active process that generally involves a process that generally involves a gas gas gland.gland.

The gas gland is rich with capillaries The gas gland is rich with capillaries and acts to concentrate oxygen until the and acts to concentrate oxygen until the pressure of oxygen in these capillaries pressure of oxygen in these capillaries is greater than in the swim bladder.is greater than in the swim bladder.

Oxygen will then diffuse from capillaries Oxygen will then diffuse from capillaries associated with the gas gland into the associated with the gas gland into the swim bladder, causing it to inflate, and swim bladder, causing it to inflate, and allowing the fish to rise.allowing the fish to rise.

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Maintaining Vertical OrientationMaintaining Vertical Orientation

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Maintaining an Upright PositionMaintaining an Upright Position

If you start to lose If you start to lose your balance, your balance, what do you do?what do you do?

You stick your You stick your arms out to your arms out to your sides.sides.

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Angelfish use their fins to maintain Angelfish use their fins to maintain “balance”“balance”

I once found an angelfish in a batch of half-grown juveniles that had I once found an angelfish in a batch of half-grown juveniles that had no pectoral fins. (I have no idea how it lost them – but the fins were no pectoral fins. (I have no idea how it lost them – but the fins were completely gone, and I had never noticed any swimming problems in completely gone, and I had never noticed any swimming problems in any of the fish in that tank before.)any of the fish in that tank before.)

This fish would work its muscles very hard as if it were using its This fish would work its muscles very hard as if it were using its pectorals, and could often maintain a tenuous vertical position. pectorals, and could often maintain a tenuous vertical position.

It also used strategies such as resting between a lift tube and the side It also used strategies such as resting between a lift tube and the side of the tank. of the tank.

The least little disturbance, or even the challenge of trying to eat, The least little disturbance, or even the challenge of trying to eat, would send this fish tumbling wildly out of control in all directions.would send this fish tumbling wildly out of control in all directions.

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Angelfish use fins to control pitch, Angelfish use fins to control pitch, roll and yawroll and yaw

Figure from http://www.geocities.com/aquarium_fish/how_fish_swim.htm

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Angelfish FinsAngelfish Fins

Pectoral Fins act as rudders and hydroplanes to control pitch and yaw. Also act as brakes.

Dorsal Fin controls roll.

Anal Fin controls roll.

Caudal Fin provides thrust and controls direction.

Ventral Fins help control pitch.

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Efficient MotionEfficient Motion

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How many of you swim?How many of you swim?

After an hour of swimming, how do you feel? After an hour of swimming, how do you feel? Tired?Tired?

Could you swim all day long? Probably not – Could you swim all day long? Probably not – you would be exhausted long before the day you would be exhausted long before the day was done.was done.

So how can fish swim with becoming worn out?So how can fish swim with becoming worn out?

How do angelfish move efficiently?How do angelfish move efficiently?

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First let’s look at how they moveFirst let’s look at how they move

The The musclesmuscles provide the power for swimming and constitute up to provide the power for swimming and constitute up to 80% of the fish itself. Muscle blocks are arranged in multiple layers 80% of the fish itself. Muscle blocks are arranged in multiple layers ((myomeresmyomeres) arrayed in several directions that allow the fish to ) arrayed in several directions that allow the fish to move in different directions. move in different directions.

Fish swim by contracting and relaxing a succession of myomeres Fish swim by contracting and relaxing a succession of myomeres (muscle blocks) alternately on each side of the body. (muscle blocks) alternately on each side of the body.

The alternate shortening and relaxing of successive myomeres The alternate shortening and relaxing of successive myomeres bends the body first toward one side and then toward the other, bends the body first toward one side and then toward the other, resulting in a series of waves traveling down the fish's body. resulting in a series of waves traveling down the fish's body.

This action starts at the head and progresses down toward the tail. This action starts at the head and progresses down toward the tail.

The The skeletal systemskeletal system acts as a fulcrum for the muscles. acts as a fulcrum for the muscles.

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Diagram showing sinusoidal wave Diagram showing sinusoidal wave traveling down fish’s bodytraveling down fish’s body

Figure from http://www.geocities.com/aquarium_fish/how_fish_swim.htm

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Now let’s look at how they move Now let’s look at how they move efficiently…efficiently…

For us to move efficiently, we For us to move efficiently, we need to push against something need to push against something that has greater inertia than we that has greater inertia than we do. We push against the ground do. We push against the ground when we walk. Swimmers will when we walk. Swimmers will push off from the side of the push off from the side of the pool to get a faster start.pool to get a faster start.

Fish also need to push against something to move – but Fish also need to push against something to move – but water by itself does not provide much inertia, because it water by itself does not provide much inertia, because it can be easily pushed aside.can be easily pushed aside.

So simply wriggling or flapping the tail will not give the So simply wriggling or flapping the tail will not give the fish very efficient forward motion.fish very efficient forward motion.

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Fish create vortices in the waterFish create vortices in the water If you create a vortex in the water, then just as a spinning top If you create a vortex in the water, then just as a spinning top

has more energy to stay upright, the spinning water has more has more energy to stay upright, the spinning water has more inertia and is harder to push aside. inertia and is harder to push aside.

Fish create vortices (cause the water to spin) with the motion of Fish create vortices (cause the water to spin) with the motion of their body and fins. This provides something the fish can push their body and fins. This provides something the fish can push against to propel itself forward.against to propel itself forward.

Figure from http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/Anatomy/http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/Anatomy/Swimming/Information/index.phpSwimming/Information/index.php

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The vortices have substantial The vortices have substantial inertiainertia

The spin of these vortices is strong enough that they stay in place The spin of these vortices is strong enough that they stay in place long enough for the fish to push against them. The fish’s motion long enough for the fish to push against them. The fish’s motion is similar to sliding through a series of pegs that it pushes against.is similar to sliding through a series of pegs that it pushes against.

The vortices actually stay in place long enough that another nearby The vortices actually stay in place long enough that another nearby fish can take advantage of them. fish can take advantage of them.

Figure from http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/Anatomy/http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/Anatomy/Swimming/Information/index.phpSwimming/Information/index.php

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ReferencesReferences

I hope you enjoyed this presentation. Here are references I used in I hope you enjoyed this presentation. Here are references I used in putting this presentation together. You can get more detailed putting this presentation together. You can get more detailed information from these sources on line.information from these sources on line.

http://www.news.harvard.edu/gazette/2000/03.23/efficient.htmlhttp://www.news.harvard.edu/gazette/2000/03.23/efficient.html http://www.hno.harvard.edu/gazette/2003/12.04/15-fish.htmlhttp://www.hno.harvard.edu/gazette/2003/12.04/15-fish.html http://www.geocities.com/aquarium_fish/how_fish_swim.htmhttp://www.geocities.com/aquarium_fish/how_fish_swim.htm http://www.ece.eps.hw.ac.uk/Research/oceans/projects/flaps/http://www.ece.eps.hw.ac.uk/Research/oceans/projects/flaps/

swim.htmswim.htm http://www.amonline.net.au/FISHES/students/dissect/http://www.amonline.net.au/FISHES/students/dissect/

swimbladder.htmswimbladder.htm http://lookd.com/fish/swimming.htmlhttp://lookd.com/fish/swimming.html http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/http://www2.biology.ualberta.ca/jackson.hp/IWR/Content/

Anatomy/Swimming/Information/index.phpAnatomy/Swimming/Information/index.php

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The EndThe End