Not All Fish Follow the Laws of Physics

Written by on October 23, 2012 in Marine Life
Here you can see just how reflective sardines are.

Here you can see just how reflective sardines are. Photo credit: ShadowSylph via photopin cc

A new study shows that some silvery fish (herring and sardines) are breaking a basic law of physics: the law of reflection.  Researchers from the University of Bristol found that this adaptation has helped them evade predators.

Reflective surfaces, like the bodies of these fish, polarize light.  When light polarizes, its reflectivity drops.  In the ocean, this would make fish, like herring, easier to spot.

The researchers found that the fish’s skin, which typically contains only one type of guanine crystal (responsible for producing the pearly, iridescent look), actually contained two different types, each with different properties.

Had the fish only contained one type, the light would fully polarize, causing a decrease in reflectivity.  However, the combination means the fish’s skin does not polarize the reflected light, allowing it to remain highly reflective.

“We believe these species of fish have evolved this particular multilayer structure to help conceal them from predators, such as dolphin and tuna,” explained Dr. Nicholas Roberts from Bristol’s School of Biological Sciences.

“These fish have found a way to maximize their reflectivity over all angles they are viewed from.  This helps the fish best match the light environment of the open ocean, making them less likely to be seen.”

Pacific sardines. Photo credit: SWFSC/NOAA.

Pacific sardines. Photo credit: SWFSC/NOAA.

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Copyright © 2012 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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