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Fresh water fish breaking ability

Fresh water fish breaking ability

Fresh water fish breaking ability

I have observed a particular type of freshwater fish that appears to possess the ability to "instantly" stop its forward movement in water.  

When this fish employs this behavior, there is no "slow" stop or "gliding" stop but an instant stop as though the fish had physicaly run into an invisible barrior. In a rough calculation of the mass and corresponding forward momentum of this fish, it appears that the expected inertia is greater than the surface area of the fish's fins available for applacation of opposite breaking force.  

The best example that comes to my mind with this fish is something like opposing magnetic forces where the fish is able to instantly "stick" in place in the water.  

Does anyone have a fluid dynamic theory or molecular chemical explanation for how this fish is able to seemingly overcome Newtonian mechanics?

thanks.. i'm new to this forum
jim coster, esquire, pittsburgh, pa     

RE: Fresh water fish breaking ability

I'm guessing that in a high speed video capture, you'd see the fish bend its body laterally, perhaps both ways in sequence, and then straighten out.  Quickly.

Mike Halloran
Pembroke Pines, FL, USA

RE: Fresh water fish breaking ability

If I had such questions, I'd call Donald Webster:


I had a grad level class he taught in the "fluid mechanics of organisms."  Fascinating stuff.  Your question is right up his alley.  I think Dr. Webster has done some work with military grants too, possibly of interest to you since you stuck 'military' next to your name.  If the stories are true, the guy had blue crabs flown in to Atlanta from the coast, and stuck them in the sediment transport flume, with die tracers tied to dead shrimp for one of his study programs.

If I were to take a quick stab at answering your question directly, though, I'd say first off that the stopping probably isn't quite as 'instantaneous' as you think, and second off that the fish is using its whole body to stop, not just the fins.  Fins on fish are mostly for fine-motion-control, they get their acceleration (and therefore deceleration) from the body and tail.  Sorta like the difference between ailerons and flaps on an airplane, only a lot more pronounced.  


Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Fresh water fish breaking ability

messers halloran and beej67:

thank you for your reponses.  

i am an armchair quantum mechanics afficinato so my initial conclusions to many perplexing matters often look to "conspiratorial" quantum behavior rather than more concret (and plasible) causal relationships.

i will, however, attempt to video this fish to determine if the kind of body movements you have suggested can be detected prior to "full stop" forward movement.  i shall also add professor webster as a future research contact.

now, if any reader out there wants to advance a quantum field theory of certain fish tapping into forces existing at the atomic level, please post your thoughts.

jim coster


RE: Fresh water fish breaking ability

I've found that breaking freshwater fish works best at below freezing temperatures.

RE: Fresh water fish breaking ability

Have you considered that the fish may induce drag forces by manipulating it's scales in small motions probably almost un-observable by human eyes?

By no means am I a fish expert but looking at the history of humans trying to replicate animal motion (ie. flight, etc) that there is a lot more going on than meets the eye in animal motion. Have to look at all the little things animals are capable of physically before looking at a more complex/mysterious explanations. Very interesting topic though.

RE: Fresh water fish breaking ability

hi trippl,

thanks for your reply.  admitedly, the question i have raised is based solely upon visual observation without any kind of testing at all.  with that said, let me try to quantify as much as i can about the observed phenomina.

1. the tank in question is a 75 gallion conventional glass rectangular fish tank.
2. this tank has an undergravel filter and top filters both of which circulate air through out the tank.  there is also a "waterfall" type duel paper mediam wheel water filter on the top of the tank that circulates a steady stream of water from the inside bottom of the tank to a discharge point on the top of the tank.
3.  the tank's dimensions are 18" x 21" x 48".  the fish in question is approximately 1 1/2" head to tail and 3/4" bottom of stomac to top of back fin. the "thickness" or width of this fish is approximately 3/8th".
4.  when food pellets are placed in this tank, visual observation indicates that there are strong water currents through out this tank with food particles circulating through out the tank within less than a minute.
5. the fish in question has 7 fins. 1 fin along its back, 1 tail fin, 1 stomac fin, 2 fins on its lower side below its "chin" and 2 fins on the left and right sides of the front of its body at the edge of its "jaw".
6.  this fish can move like all the other fish in a "gliding" motion through the water or employ the questioned "jerking" motion where it advances then instantly stops.  it is this "jerking" motion through the water that seems to defy inertia and basic fluid dynamics.
7.  i have 35 fish in this tank including two of the subject fish of which i speak.  only the two same phylom fish i have noted have the "instant stop" capability.  the other 33 fish have not exhibited this ability.

thanks again for your comments.

RE: Fresh water fish breaking ability


I am intrigued. What kind of fish is it?

You taking into account all frictional forces over the body of the fish due to flow? How about the force/velocity of the fish's fin(s) forward stroke (taking the flow of the water into account)? A fin just stuck straight out is going to have less force than if the fish is "stroking" it forward as it stops. The shape of the fins will also effect the force. This will be very difficult to model since I'm sure the shape of the fin changes as it moves. I'm sure there are many, complex, un-noticeable (fast) movements occurring to cause the fish to show this ability and behave this way. Go swimming and think of all the nuances to your movement through the water. Very complex.

As to the type of fish being the only to "exhibit this ability". Could be that this fish has learned or programmed behavior that dictates this ability and behavior. Animal behavior is complex in itself. Just because one fish behaves this way does not make it impossible for another fish to do. I have the ability to run as fast as possible down the office corridor, but I never have.


RE: Fresh water fish breaking ability

The fish you are talking about are probably a variety of Darter. Their motion is where the name comes from. It would be interesting to see high speed video of their movement.

RE: Fresh water fish breaking ability

hello trippl,

1. the two fish in question are called "electric blue rams."
2. both of these fish have a structural design common to fish - somewhat elongated oval shape, delta, butterfly shaped tail fin, long flat dorsal fin, triangular shaped left/right body fins.
3. undulating movements are observed in the dorsal and tail fins as these fish move.  the left/right front body fins also flap or "beat" exceedingly fast much like a humingbird's wings.
4. both fish apeear to be able to "float along" in the water like all the other fish but to move in a jerking, haulting fashion at will.
5. water is municipal water system pittsburgh, pa h20 tap water with a very small percentage of chemical additiive.  standard fresh water viscosity is assumed.
6. the fin movements of this fish are very similar to the fin movements of all the other fish in the tank. forward velocity force propulsion over distance/time appears to be consistent with other like sized fish fin movement.
7. without knowing much about calculus, if one assumes a standard mass + velocity = momentum/inertia taking into account the friction coefficient of the surrounding medium, this fish is not acting right.  this fish will "glide" as newton would predict after fin force propulsion is applied. but then it will suddenly "freeze" in place as though it has become magnitized with the water instantly overcoming all inertia.
8. in all other aspects, these electric blue rams act just like the rest of the fish in the tank.  the instantaneous "freezing in place" behavior has only been observed in these two fish.
9. interestingly, these fish can "freeze in place" while swimming laterally, left/right or vertically "up" or vertically "down" raising another question of not only overcoming inertia but gravity as well.
10. even assuming this fish is employing "reverse thrust" having its fins act in opposite to the direction of travel, water like air is a medium where instantaneous cessation of movement is difficult or impossible to achieve.  neither fighter jets nor space rockets have been able to achieve "instant" course corrective movements.     

RE: Fresh water fish breaking ability


I'm sure that the fish appears to your human eyes to "freeze" in place instantly. I assure you that it is not instant. It is only instant to your eyes which are relatively slow compared to the movement of fish. I assure you that there are many, many movements that the fish is doing that you can not possibly see with your eyes.

The fish is a master of water. It can control it's movements in water and appear to stop on a dime. I assure you that the fish is using it's body and fins to assert a force over a very short amount of time and distance. Now if the fish starts transporting from one side of the tank to the other then you may be on to something.

To fully understand the forces and actions going on here you should have an understanding of basic fluid dynamics, physics (conservation of energy, impulse force, etc). And you may want to employ the use of a high speed camera to see exactly what is going on with the fish's motions. Maybe could drop some non-toxic dye in the water to see the eddies created by the fish's fins.

Also, I assure you that it takes much much less energy for a fish to stop abruptly in water than it does for a rocket or jet to do so in air.

Send a video  or something. Would like to see this.

Check this out: http://physiologyonline.physiology.org/content/17/6/235.full

RE: Fresh water fish breaking ability

Here's a good video of the Electric Blue Ram (the fish in question)


They do have interesting movements, but nothing magical or inexplicable by the laws of physics.

RE: Fresh water fish breaking ability

hello trippl....

thank you for the additional material which i will review.  i will post a video of this fish if i can capture the subject movements with some clearity.
jim coster

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