Why are warm climate fish more colorful than cold climate fish?

Factual Questions
1

I have an aquarium. I got a new fish (a Cichlid, not that it matters). It is a beautiful bright gold and black. My daughter asked me where the that kind of fish lived in the wild I told her about how Cichlids come from African lakes. Cichlids are often referred to as Africans.

I used to have different, non-Cichlid, community fish in my aquarium. She asked where those fish came from and I told her that most of them come from South America.

She said that she really likes the bright colored fish that she sees in the Caribbean when she goes snorkeling.

Then, bless her soul, she asked me why the fish around here (upper midwest, USA) are so boring in color. I told her that the cold water fish don’t come in bright yellows and blues and oranges and reds.

You can see it coming can’t you. She then asked why not?

And I cannot find out why not. It’s driving me nuts.

Can someone tell me why warm water fish are so colorful and cold water fish are not?

2

I am afraid the only answer I have isn’t a very good one, and I am sure it is over simplistic. But this is how I explained it to my kids.

Look at the birds of North America. For the most part, they are rather drab. Look at the landscape of North America, shades of brown and green for the most part. Therefore, one would assume the fish would also reflect this drab color scheme in order to blend in.

In the Tropics, the birds and vegatation are more brightly colored, therefore the fish would have to be as well, to mimic vegatation and the surroundings.

3

The fish are underwater. Why would they have to match the birds and vegetation, which are not underwater?

4

Not a bad theory Lyllyan, but it doesn’t sound complete.

How did you explain the bright colored Cardinals, Orioles, Blue Jays, Tanengers, and Indigo Buntings to your kids?

And while the camouflage idea makes some sense for the Caribbean fish in the coral reefs, I don’t think the inland lakes of Africa and South America are very colorful (though I’m just speculating because I’ve certainly never been scuba diving there.)

5

Could it possibly have anything to do with those animals being closer to the equator, and getting more (stronger?) sun/UV light than the animals in, say, North America and Europe? It seems like the more colourful animals live in higher concentration in forests and rainforests around the equator.

6

Oh, I just remembered… quite a few aquarium fish have been selectively breeded for colour, too. Their brothers and sisters in the wild might be quite a bit more drab. (Not all fish, but some… like Goldfish, off the top of my head.)

7

If the pigments that cause brighter colors also offer protection from UV rays (or are very strongly associated with such a trait), then this would make sense.

8

jinwicked, your observation seems right about there being more colorful fauna as one gets closer to the equator (yet I’m still troubled by birds like Cardinals, etc. to firmly agree on this hypothesis).

I can’t speak for the water clarity in the inland lakes in South America and Africa, but certainly the water clarity in the Caribbean is substantially better than the lakes around here.

Your follow-up comment about aquarium fish being bred for color may be the answer for fresh water African and South American fish, but it doesn’t explain the bright colored salt water fish.

And I don’t see the connection between more sunlight getting deeper into the water and fish color, unless ultrafilter’s hypothesis is correct (that color may offer protection from UV rays).

Do UV rays even penetrate very deep into the water?

9

I was told that it had to do with mating.
Colour is used to attract mates. The more exotic/colourful the better for breeding the worse for not being eaten (easier to see easier to eat). So the colours tend to be a compromise as to how wild you can get appearance-wise before you become the prey of choice for predators.
In water, colours get washed out after a relatively short distance (has to do with how far various waves of light (colours) can travel before being absorbed by the water). So really bright colours or totally drab colours are basically the same camo wise in the ocean as far as distance is concerned. Up close the shapes and colours actualy do blend into corals relatively easily and there are places to hide if it doesnt, so attracting mates plays a stronger role than hiding from predators. You’ll notice that open water fish aren’t as extravagantly coloured as those living around coral and other hiding places.
That was more or less how it was explained to me, or at least what I understood of what was explained to me. :smiley:

10

By the way, the breeding-for-color aspect is why I didn’t use the very colorful Koi in my outdoor pond as examples.

11

rabbit, assuming what you were told (or what you understood you were told. ~grin~) is true, it still seems only a partial explanation.

What about the colorful African Cichlids?
And if bright colors and drab colors are virtually the same under the water camouflage-wise, then why wouldn’t there be colorful fish around me?

12

David Attenborough addressed this in one of his books (sorry that I cannot remember which one). The intense and varied colors are used to attract mates of the same species in densely (fish) populated areas. I cannot think of any area with strikingly colored fish that is not teeming with schools of small fish. As evidence he states that in instances when brightly colored fish have been swept away to a more lonely, isolated environment, the colors fade after a few generations.

13

That could be part of it as well. Tropical or highly productive environments tend to have relatively few individuals of any one species, but a vast array of different species. Less productive systems are characterized by having fewer species present, but huge numbers of them.

So in a big lake containing 200 species of cichlid, you’d want to be able to tell your kind from the others, and if you were all a drab brown or silver, that might be hard. If you live in an oligotrophic lake with 4 species present, you don’t need to be that different or to stand out that much to find your own kind.

Corals reefs themselves are somewhat colorful, so sea fish can blend into them even when colored electric yellow or red. Much of the predation by sharks takes place at night as well, when your colors aren’t gonna get you in too much trouble. During the day you want to defend your little bit of territory and attract mates, and since you’re in such a productive envirnment, there’s tons of other fish and a lot of crowding. Due to the proximity to the equator, breeding seasons are also longer and more drawn out, so you’re spending a greater proportion of your time flashing yer colors to everyone else than if you lived in a cold water environment where breeding took place over a short time once a year.

Also note that cold water fish do color up at certain times of the year, even if not as much as their tropical relatives. Take a look at sockeye salmon on their way up the rivers - bright red. Most fish will at least intesify their colors during breeding, and there are some nicely colored cold water fish who retain them year round, like brook trout.

14

Not all salt water or warm water fish are colorful. There are mullets, and various trout which are quute drab to all but another trout or mullet.

My WAG is that colorful fish are also shallow and clear water dwellers by nature. In clear shallow water visible cues are going to be meaningful. Your more plain looking fish are likely either going for camoflage or reside in an area where being colorful isn’t really useful as there is poor or no visibility.

15

warning – speculation ahead! – warning

Very generally, there are <figures mentally>…three!..uses for color amongst animals:

  1. Attract mates
  2. Warn predators
  3. Hide from predators

Item #1 should be fairly obvious. Item #2 is commonly found in posionous species (or those who mimic them). A variant, I suppose, might be the use of color to warn one’s fellows (as in white-tailed deer). Various forms of camouflage fall under the third category.

Now, it seems to me that for bright-colored fishies, the bright colors can serve equally well for items #1 and #3 (the colors can help to disguise a given individual fish in a school, much as a zebra’s stripes help to disguise an indiviudal amongst the herd – that is, the rest of the school acts as the background against which an indivdual can camouflage itself).

It seems to me that warm-climate fishies tend to congregate around coral reefs and the like. And, of course, whenever there is a large congregation of critters, predators will also tend to congregate. So, these warm-water fishies have two problems. The first is to mate. With so many other fishies in the area, members of a given species need to be able to identify one another. Bright, wildly-varying colors would work well in this regard. The second problem is survival. This is aided by gathering in large numbers, whereby any individual gets “lost in the crowd”, and the bright colors further help in this regard, as mentioned above. Predators, then, can generally only make out a generic “cloud” of fish, and cannot single out any one individual.

In colder climates, one tends not to see such gatherings of various fishies, except, perhaps, during seasonal mating periods. As such, schooling is typically less pronounced, therefore bright colors would only serve to make one stick out, rather than offer a source of camoufllage (during mating seasons standing out from the crowd is a good thing, of course). Where one does find schools (typically in river environments), drab colors or simple countershading probably work better than the bright, showy colors of more open-environ, tropical fish.

(Please forgive any factual errors with respect to what kinds of fish one finds where. I am regrettably quite ignorant about much of the natural world, and the above is based on speculation from an adaptive point of view.)

16

“I was told that it had to do with mating”

If I remember correctly, fish don’t get too specific when they mate; after a female, wildly attracted by a males bright colors, send forth her eggs, any male fish of the correct species can provide sperm. If the males are territorial, the drabber males would have an advantage, because he would be less noticeable to the male whose territory he was poaching on. Unless fish don’t see color. In which case the female wouldn’t care how bright the non-drab male was …

Or am I missing something?

Maybe the question is being approached from the wrong direction? Prehaps there is an adaptive reason for cold climate fish to be drab?

And has anyone determined if brightly colored fish are brightly colored to other fish or predators?

17

OK, here are the proposed theories so far on why warm climate fish are more colorful than cold climate fish …

  1. Protection from UV rays. I’d think if this were the reason to evolve color, all the fish would be black.

  2. Camouflage in the coral reefs. This makes a lot of sense, but it doesn’t provide an explanation for the African Cichlids, who are brightly colored but don’t live in coral reefs. If the only colorful fish in the world existed in coral reefs I believe we’d have our answer. Unfortunately that’s not the case. Hence my OP.

  3. Shallow/clear water makes visible cues more meaningful. Hmmm. While not particularly clear, many of the lakes up here are quite shallow. And I could just as easily come to the opposite conclusion about clear water. In clear water, wouldn’t it be less important to be brightly colored? And this doesn’t necessarily cover the African Cichlids. I doubt that the inland lakes in Africa are any clearer than the midwestern lakes around me.

  4. Camouflage in large schools. My main thought here is that color is irrelevant to the benefits of an individual “getting lost” in a large school. The schooling behavior itself is what results in the increased survival odds. Drab colors would be just as effective in a school as bright colors.

  5. Species identification in bio-diverse environments. While this seems like a stretch, this makes the most sense to me. My hesitation is that nature typically doesn’t have a problem with males and females of a species finding each other, regardless of color. In some animals, color certainly plays a role in mate selection, but I don’t think this generally has anything to do with making sure their mate is of the same species.
    A couple of posters pointed out that not all cold water fish are drab, nor are all warm water fish colorful. True enough. There are always outliers on the curve. I don’t think there would be any disagreement however about where the majority of fish in a region fall in the “color curve”.

j66 asks a couple of important questions that remain unanswered. “Is there maybe an adaptive reason for cold climate fish to be drab?” “Do other fish or predators see the bright colors that we see?” Or the parallel question of “do fish that look drab to us look colorful to other fish?”

I’m going to email Colibri to see if he has any thoughts to share on all this. If there are other biologists out there I’d love to hear from you.