Are the Muskies You See Really That Big?

Muskies underwater are only 3/4 of the size they appear.  (c)Eric Engbretson

One of my favorite websites for fishing information is Lake Link. The fishing reports posted on this site by the thousands of fisherman who fish the many lakes in the Midwest region can be useful, informative and entertaining. While some of the most experienced and knowledgeable fisherman post fishing reports and their observations while on the water, I am constantly amazed at one glaring mistake so many fisherman make. That error is not understanding the magnifying effects of water. Simply put-fish look bigger under water than they really are. The message boards on Lake Link are filled with hundreds of eye-witness accounts of fisherman reporting large muskies that "swam right next to the boat that were 50 inches!" Could there really be that many 50 inch muskies swimming around? The answer is a disappointing "No".  What these fisherman all fail to realize is that fish in water, viewed through air are only 3/4 of the size they appear to be. So, all those mammoth 50 inch fish are really just ordinary 37.5 inch long muskies.

Scuba divers all understand that one attribute of water is that when viewed through a prism of air, also known as a diver's mask, objects appear much larger than they really are. Underwater, a 45 inch musky will look a 60 inch whopper! Fisherman often ask me how large the fish are that I see underwater. Honestly, most fish look big underwater, and big fish look like Godzilla. In my early days of diving I was convinced that each musky I encountered was a world record.  Many scuba dives later, I've come to better understand the illusion, and realize that reports of monster muskie that "got off just as they were about to be netted" were likely ordinary sized fish.

Some may argue that the fish lined up exactly with something on the boat that's of known size and reference, but the viewer doesn't understand the illusion facing scuba divers all the time. Boats and the objects on them are poor comparison tools as they're in the atmosphere, visually accurate in size, while the musky is underwater, distorted in size. To test this concept yourself, measure your hand. Then lean over the side of a fishing boat or dock and stick it about a foot underwater. Hold the ruler above the surface while viewing your submersed hand, and measure it best you can. How'd the numbers come out? If you did this correctly, your dry hand will be roughly ¾ the underwater hand size.

While the fishing reports on websites like Lake Link can be valuable research tools, don't be fooled by eye-witness accounts of large fish that were seen underwater. They just weren't that big.