ArticlesQ: Why do fish swim in schools?
[This isn’t a riddle, or a trick question. It’s a legitimate question of piscean behaviour.]
A: To reduce the chance that each fish is eaten by a predator.
How does that work?
The normal explanation goes as follows:
Imagine you are a solitary fish and a hungry predator sees you. You will be eaten.
Now, imagine you are in a school of 100 fish, and a hungry predator sees the school. You only have a 1 in 100 chance of being eaten. (Assuming the predator only has a stomach big enough for one of you.)
I’ve heard that explanation given many times, and, even as a kid, I found it unsatisfying.
The ratio of predators to prey dropped from 1:1 to 1:100 between the two scenarios. What happened to all those other predators who were feasting on your friends in the school? A fairer way of looking at it would be: Imagine you are in a school of 100 fish, and 100 hungry predators see the school…
When I was an adult, someone (probably my father, Joe) explained to me a much better model for explaining how schools of fish reduced the risk of being eaten. Rather than looking at it from the perspective of the prey, look at it from the perspective of the predator.
Imagine you are a predator chasing solitary prey fish. Every day, you find one fish and you eat it. That gives you enough energy for another 24 hours, which is how long it takes until you find another solitary fish.
Now imagine you are a predator chasing prey fish that swim in schools. On the first day you find a school of fish, and eat one. Your stomach is full, and you have enough energy for another day. However, the fish are clumped together in groups of 100, so it likely to be another 100 days before you come across another school. You starve.
Alternatively, you could grow a huge stomach that fits 100 fish, but that has a huge cost.
So, having prey fish swim in schools makes it more difficult for predator fish to survive between feeds.
The same logic applies to plague insects, most ungulates, and, I argue, cable television shows.
My experience with cable TV channels was that they mainly had crap on. Often they would have marathons, where they would show nothing but the same crap TV series for 24 hours straight.
Every now and again, they randomly have show that I would like… and they would put it on as a 24 hour marathon.
24 hours is more than anyone can reasonably sit through. It is more than most recording equipment can handle. Either you don’t like the show, or you can’t possibly watch it all. It is guaranteed to minimise the number of viewers.
I see a direct analogy here with the schools of fish. The show is the prey fish. The viewer who likes the show is the predator.
The only thing missing here is the question of why the cable channels would want to try to starve the viewer of the shows they like. That has me stumped. Any ideas?
Comment by Sunny Kalsi on July 26, 2007
Yow that was bumpy. Your analogy is weak, and this is coming from a person who makes ridiculous wild analogies.
The easy answer is as follows: The less TV you are able to watch, the less you will watch. The less you watch the more the cable TV station can repeat it, allowing them to reap the profits.
In your analogy, this would mean that the prey fish have to pass the predator fish every day. There is exactly one predator (since everyone has to watch every show. Just because a prey fish is “eaten” for one predator does not mean they’re “dead” for another). If the fish passed by one-by-one, slowly, the predator could eat them at his leisure. However, if they pass by all at once, then the predator has to wait for the entire school to pass by every time it wants to eat.
Comment by Julian on July 26, 2007
Sunny,
I was stuck wondering why the TV channels would want to starve their viewers. I am impressed with your insight that TV stations might not always want to maximise viewers for a particular show.
Free-to-Air TV stations want to find
max(#viewers * advert revenue/viewer) - content_price.However, cable TV stations want to find
max(subscriber months - content_price).Preventing a subscriber from seeing every episode of their favourite show might leave them hanging for another month trying to catch it again, without the station having to pay for new content! Interesting!
Your extension of my analogy has left me nonplussed though. Making the prey move and the predator stay still doesn’t seem to change the dynamics.
Comment by Bork Blatt on July 26, 2007
Well, the analogy may be flawed, but I enjoyed it. A nice way to go crazy is to take a good analogy and examine it for holes.
One place I think your analogy holds well, is that for a predator, the goal is max(food/effort) and for just about any business, the goal is max(profit/(effort + cost)). I guess this is still slightly better than the public company: max(share price/(effort + cost)).
Comment by Julian on August 26, 2007
Actually, Bork, I have heard a related story about zebras. They herd, and they have a weird sort of camouflage that doesn’t really blend in with their surroundings. The claim was that the black-and-white stripes made it difficult for a predator to tell where one animal stopped and the next one started, especially when they were moving.
I guess a zebra does blend in with its surroundings, if its surroundings are other zebras!
I am not sure how you would test such a hyopothesis.
Comment by Julian on January 6, 2010
Upon re-reading my comment some years later, I have *no idea* how the zebra comment is even remotely related to Bork’s response. Sorry, Bork.
Comment by Aristotle Pagaltzis on January 6, 2010
Were you in altered state when you wrote it?
Comment by Julian on January 8, 2010
It was over two years ago. I can’t remember last week!
I went to look it up in my “Altered State Diary, 2007”, but the relevant section is just filled with the word “artichoke” neatly written out 500 times, so I can’t be sure.
Comment by Aristotle Pagaltzis on January 8, 2010
Such a pity that your records don’t tell us anything. Oh well.