Do Fishes Get Hurt when They are Thrown Back Into the Water? Truth or Myth? The Explanation Behind the Water Surface Impact.
Posted by Leo Sheng at 2:40 PM
Hello, Blog Readers!
It's been a long time since I have written something informative here on my fishing Blog; thus, today I'm bringing you another post of my "Truth or Myth" series. The last "Truth or Myth" post that I have written was on fish hibernation, which you can access here.
So, what exactly drove me to write about this topic?! The truth is that just recently, I've received some constructive criticism on my YouTube Channel regarding my CPR methods (Catch-Photo-Release) -- mainly how I "throw fish" back into the water instead of "placing them" and "letting them swim away." The whole conversation is seen below:
A heated discussion on my YouTube Channel. Heh. However, please keep in mind that I always accept constructive criticism there.
According to the person who wrote the comment, I was "treating fish like garbage and harming the fish by throwing them back." Also, I was "showing people that it's okay to throw fish," concluding that the same was "not proper catch and release." In the end, the person stated that I was "not setting a good example."
Above is a video of my fishing at Gropp Lake and Crosswicks Creek in NJ, where I actually throw back lots and lots of small fishes. Is it good or bad to throw them back like that?
In response, I decided to google some credible sources that showed that it was absolutely fine to throw fish back into the water from reasonable heights, all without damaging the fish. As you guys know, I am a scientist -- thus, I need my facts before saying something. And, for my surprise, I wasn't able to find anything on it. What I found were multiple websites that enforced the fact that fish should not be thrown back into the water, but placed instead. However, those websites never gave the science behind it or any credible information behind their ideas! All that was mentioned was "to prevent the fish to get into a state of shock, they should be placed instead of throw." Very shady, seriously. After all, I have thrown thousands of fish back into the water and only on rare occasions I have seen them achieve a state of shock, mainly because they hit something on their way down.
In the end, even after googling, I was unable to find out if throwing them back into the water was harmful or not. Thankfully, I am a Physicist and Angler; thus, I don't necessarily need other sources. I can just write my own! Therefore, the main question here is: does fish get hurt when you throw them in the water? Myth or Truth? What do you guys think? Heh. Well...don't think too hard -- the truth is below.
So, let's get cracking! Let's talk a little bit about Physics today (it was my major, after all).
A. About human beings and free fall...
Before talking about fishes, let's just think about us -- human beings. What exactly would happen if a person fell from a very high place into the water? Would that person survive? For example: what would happen if someone fell from a helicopter or an airplane into the sea? What do you guys think?
According to science, the truth is that the person would very likely be flat dead. There is something in the field of Physics called "Terminal Velocity." By definition, that would be the maximum velocity that something can achieve during a free-fall. When reaching terminal velocity, chances are that the human being who fell in the water is dead. As a matter of fact, there have been only a few recorded incidents in history where persons achieved terminal velocity and actually survived when crashing on the surface of the water.
(1) How long does it take for a person to achieve terminal velocity?
That's a very complicated question because terminal velocity actually depends on many different variables, such as the weight and the height of the person (i.e. the shape), the posture of the person during the fall, the atmospheric pressure, etc. One should note that different objects/organisms have different terminal velocities.
However, it's estimated that it takes about 10-14 seconds of free-fall for a person to achieve 99% of its terminal velocity, which would be in the range of 117 to 125 mph. That would be equivalent to a fall of about 1800-1900 feet!
(2) Why does the person die upon impact?
One would think that the height doesn't really matter. In other words, a person falling into the water from any height would be able to break the surface of the water and swim away just fine! Well...That's not the case!
The problem itself is not the water, but actually the falling person! When organisms at high-velocities have an impact with something, believe it or not, they behave like fluids! Thus, one can say that higher the energy the person has during the fall, less important is its "binding energy." By definition, binding energy is basically the amount of energy that is required to "keep things together" or "pull things apart." So, in the Physics language, if the kinetic energy of a body is higher than its binding energy, the same behaves like a fluid (like you are breaking apart).
So, as a Physicist said one day: "So, when you fall from a great height and land in water there’s a bunch of kinetic energy going every which way. The water continues to behave like water, but since the kinetic energy in different parts of your body are greater than the binding energy keeping them connected, then the body as a whole will act more like a fluid. That is; it’ll “splash.”"
So, as you can see, at high-velocities you have a crash between a "liquid" (the person) and a "liquid" (the water), which would be the same as a crash between a solid and a solid. That's why people tend to say that falling into the sea from high distances is the same as crashing into plain concrete!
B. About fishes and free fall...
Now that you know what happens to a human being, let's talk about fish. Do they get hurt when you throw them back into the water? Do they get into shock because they actually "hit concrete" upon landing?
Bell and DeLacey did a research in 1972, where they actually found the terminal velocities of different sized fish by throwing them in the water from a helicopter. They actually found out the following:
(1) Fishes 4-5 inches had a terminal velocity of ~36 mph after a drop of 100 feet.
(2) Fishes in the range of 23 inches had terminal velocities of ~130 mph.
(3) The survival of fish in the range of 6-7 inches was in the 98% range for drops of 100-300 feet.
This data may look confusing, but it shows us something very important. For a fact, it shows us that smaller fish (4-5 inches) have a much lower terminal velocity than larger fish (23 inches); thus, if the distance of the fall is the same for a small and big fish, the smaller fish has a much much higher chance of surviving the fall without any damage. In the Physics language, lower velocity = lower kinetic energy; thus, binding energy of the fish is higher than its kinetic energy and its body behaves like a proper solid. A solid crashing on a liquid = survival. :)
And, as indicated in (3), the survival rate for fish in the range of 6-7 inches, which have a slighter bigger terminal velocity, is a whooping 98% for drops of 100-300 feet! Now...notice that the data mentions survival rate for impact only. In other words, the fish may still be injured after getting dropped from such height; however, it doesn't die from the impact of hitting the water. According to research, one should say that fish remain uninjured from drops in the range of <50 feet.
If throwing fish back in the water was harmful, why would certain states actually stock small fish in lakes by airplane?
Considering that most of the fish that I catch and throw back are in the range of 4-7 inches, and the fact that I am throwing them from anywhere between 5-25 feet, that means that I am definitely not hurting these fish! When they hit the water at these distances and velocities, their kinetic energy is much lower than their binding energy; in other words, they don't hit the water like it's concrete. They safely land in the water and swim away. No harm done!
As for bigger fish, the Physics itself says that it would take at least a drop of 50 feet to bring them any harm (depending on the Species, of course).
So, there you go you, fellas -- one without knowledge may think that I treat fish like garbage when I throw them in the water; however, as a Physicist and Angler, I can tell you that there is absolutely no harm to the fish in giving them some short range free fall. Of course that is taking in consideration that the fish doesn't hit anything in-between and the same doesn't hit the bottom of the water after the splash! Hah. That's one argument that folks who release fish in the water can certainly use.
Thus, the notion that "throwing fish into the water instead of placing them brings them harm" is actually a myth.
C. FAQ (Frequent Asked Questions) and additional comments...
I. From what I have just read, should I throw every fish in the water then?
The answer is no. As you read above, bigger fish have more chances of getting injured when they are thrown into the water. Also, any fish that is thrown into the water has a chance of getting injured if the same hits anything in-between or hits the bottom. In other words, make sure to throw selectively! If conditions allow, make sure to wet your hands before handling the fish and place them in the water for a proper "swim away."
According to different researches, it's fine to throw small fishes in the range of 3-15 inches; however, bigger fishes should be released in the water and after proper revival. Also, one needs to take into account that different Species have different responses to injury. Let's not forget that the Trout and Walleye are more sensitive than the Catfish and Carp. Therefore, sensitive Species of fish should be handled with more care to maximize their survival rates.
II. Can I just throw them anywhere in the water?
Once again, the answer is no. If the fish exceeds 15 inches, make sure to throw them in calm waters without currents, so that they can recover properly from the fight and go back to their natural habitat. If necessary, make sure to always revive the fish properly!
Also, never throw fish in shallow places, where they can possibly get injured after the water impact. Give your location at least a 2 feet depth for a proper throw.
III. What is the best possible way of handling and releasing a fish?
The practice of CPR starts way before landing the fish! The best way of properly maximizing a fish's survival rate is to actually ensure the following (in the order of most important to least important):
1. Keep the fish outside of the water for as little as possible to prevent anoxia. Every second outside of the water counts! More time outside = less chances of long term survival. Depending on the Species, some fish will go belly up even if they are handled for short amounts of time outside of the water (i.e. Trout, Walleye).
2. Use barbless hooks or set the hook as fast as possible to avoid internal injuries. If your fish swallowed the hook, that's already a bad sign! Just imagine someone pulling you far away while having a hook on your stomach. Even if you reach there alive, you will have some internal bleeding. That's exactly what happens with the fish. Thus, if the hook got into its stomach or gills, practice selective harvest: take the fish home for consumption or use it as bait (if legal in your state), You may cut the line and release it; however, its chances of survival will be very limited.
3. Make sure to always revive the fish properly, specially if the same is a trophy fish or a sensitive Species of fish!!! Depending on the Species targeted, there is absolutely nothing wrong in playing it with light tackle, as far as proper revival is performed. For more sensitive Species of fish, the angler should play it for as short as possible. Click here to read my post on angling duration. Remember, folks: fish do die from exhaustion!
4. If conditions allow, handle the fish with wet hands. Handling them with dry hands remove their slime coats. If you don't have the time or conditions to wet your hands, make sure to touch them for as little as possible. If you are as gross as I am, make sure to build a "slimy hand" when fishing -- in other words, don't wipe your hand every time you land a fish. Let the slime stay in your hand, so it stays moist when handling the next fish.
If all of these are followed, you can rest assured as a CPR angler. :)
Best of luck to all of us,
Long Days and Pleasant Nights,
Labels: Didactic Post