Why Are Marine Fish So Brightly Coloured?

[lgarvey]

I'm fascinated by evolution and adaptive traits and so on. And as I'm also fascinated by fish, freshwater fish initially, but now also marine fish, I'm wondering about a few things.

There's obviously a clear difference in vibrancy of colour between marine and freshwater fishes. It's obvious that certain fishes, such as a stone fish, or even a mandarin fish (it's camouflaged against the LR / Coral) has a certain colouration to avoid detection from predators or prey.

But why are the colours so amazingly vibrant in many of the marine fish compared to FW fish? Think about an orchid dottyback, or wrasse. Is the coloration largely about breeding? i.e. the brightest coloured fish is the most desirable to potential mates? Because the bright purple colour of an orchid dotty back, or say a fairy wrasse makes it very "obvious" and not at all camouflaged from potential predators. And how come marine fish are far more colourful than frewshwater?

I think this is off-topic re's fish-keeping, but I'd be interested if anyone has researched this aspect of at all.

Cheers,
L

 

[bae1994]

i think its because coral has a algea in which gives it its colour so the fish has evolved to match with the corals

also the manderins actually try to be seen and there bright colours are to trick its preditors into thinking its poisionouse

and alot of other marine fish are bright colours to tell there preditors that there poisonouse

 

[SkiFletch]

First you have to understand that the natural reef is an EXTREMELY competetive environment from a resource/nutrient standpoint. They're almost like the rainforest of the seas. So many organisms crammed into such a small place with no real available nutrients until something dies.

Because of that competition, it's my oppinion that a lot of the vibrant colors you're seeing is a result of Sexual Selection where fish compete with each other for mates, commonly through vibrant colors.

 

[bollands]

I thought some fish were brightly coloured to camoflague themselves amongst the corals

 

[Gallagher]

The 2 main reasons/therorys are bollands's, for camoflage, and also so that they can pick out their own species in the crowded, competetive reef.

 

[AK77]

Its so that your LFS can charge 10 times more than a goldfish

 

[BigTom]

The Encarta entry is actually quite good for exploring some of the ideas behind this without getting too sciencey:

http/encarta.msn.com/encnet/refpages/Ref...refid=461576303

 

[SkiFletch]

I thought some fish were brightly coloured to camoflague themselves amongst the corals

The only real examples I can think of brightly colored livestock doing so for camo against corals would be commensal crabs and shrimp that live in acropora in a symbiotic relationship. Also some nudibranchs are brightly colored to the same color of whatever they're eating to avoid detection by predators.

But fish don't really hide in/amongst corals. The exception of course is clown fish but they don't use color to hide...

 

[Musho3210]

I doubt the color is for camouflage, if so rock/sand dwelling fish would be a more dirtier color, clownfish would match the anemone in color, and fish that swim aimlessly would be colored like a penguin.

Nothing scientific in what I said, just my opinion on something I have no prior knowledge to.

 

[lgarvey]

I doubt the color is for camouflage, if so rock/sand dwelling fish would be a more dirtier color, clownfish would match the anemone in color, and fish that swim aimlessly would be colored like a penguin.

Nothing scientific in what I said, just my opinion on something I have no prior knowledge to.

I suspect it's more to do with sexual selection and competition and perhaps also to do with appearing poisonous / toxic.

It's interesting that many sexually desirable traits are actually counter survival, like the peacocks huge tail. There's an evolutionary theory that states that surviving in-spite of survival hindering traits implies "survivor-ability", and thus good genes. Certainly surviving in-spite of being a bright coloured fish amongst a number of natural predators demonstrates survivor-ability. Then again as the Encarta article discusses, colours have different degrees of visibility underwater and it depends on the optical apparatus of the fish's natural predators, or potential mates.

I was also fascinated with why marine fish, particularly tropical marine fish, tend to be so amazingly coloured compared to other fish, such as temperate marine fish and freshwater fish. But perhaps as Ski Fletch points out, it's a lot to do with the fierce competitiveness and scarcity of resources on the reef.

The Encarta article, which is a fascinating read, seems to suggest that disguise is not a prime factor for most colourful marine fish.

 

[loachman]

I'd imagine 4 things are at play.
1. Coral reefs can be very colorful, so it can act as camo when among the coral.
2. Red light is heavily filtered by saltwater, and not freshwater. So red coloration actually acts as a pretty good camo color as it's hard to see from any distance. You'll notice there are a lot of fish with predominately red or similar warm colors.
3. Reproductive benefits. Flashiest males gets the female.
4. Freshwater is much more likely to be cloudy/turbid, so the subdued colors are better in that environment.