Silver fish: Why are some fish in the Gulf of Maine silver?

Monday, October 15, 2012 by Caroline Casals

Lets look at some silver fish that live in the Gulf of Maine.

Atlantic herringAtlantic mackerelButterfishSilver hake

Wait a second, these fish are actually shiny! That has to be even worse than being all white like that albino deer.  The bottom of the ocean isn’t shiny, the middle of the ocean isn’t shiny, what on earth are these fish doing?

            In order to solve this mystery we have to remember that the ocean is NOT two-dimensional! Fish live in a 3D world, their predators (or prey) could be above them, below them, or next to them.  These fish have a dark stripe on their backs too.  If we look at them from the side, they are extremely easy to see:

Fake fish from the side

However, if we look at them from above with nothing but dark ocean below them, just how their predators might see them…

Fake fish from top

...they disappear! That works pretty well, so why not be dark blue all over, that way they could look invisible from the side too?

Well what if we look at them from below like their predators might.  Now our little fish is in big trouble!   In the ocean, the light comes from the top --from the surface -- where the sky and sun is.  Our fish is now between the light and the predator.

Shark and fish from below

 Have you ever made shadow puppets?  Well our little fish is now a shadow puppet, and she’s super easy to see!  But wait, our fish isn’t dark, she’s shiny like a mirror, and mirrors don’t block light, they reflect light.  Instead of casting a shadow, the shiny sides and belly of the fish casts light back down and looks just like the surface above. 

Pretty neat!  The only time our fish isn’t perfectly camouflaged is from the side, but the ocean is a pretty big place, so long as her predator is slightly above her or slightly below her, she’s blended in expertly!  Fish like her, that live in the middle of the ocean, not near the bottom, are called pelagic fish.

Have you seen any fish in freshwater that are also shiny?  Why might murky freshwater cause fish to have different camoflauge than in open ocean? **Bonus** next time you are in a store with fishing supplies, look at the lures section and ask yourself which lures might be most enticing to predators of shiny fish and which might attract those that hunt non-shiny fish.  Do you think these predators use the same strategies for different fish? Let us know in the comments below!

 

Learn more about brown fishred fish or go back to the start.

Photo credits:

Splash image: NOAA.  All others top to bottom, left to right: (top four)  NEFSC/NOAA, (next two) Caroline Casals, Flickr -- user tikigod



comments powered by Disqus