How Fish Swim
by Phil Pitts
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Wow! That kid swims like a fish!
That's quite a compliment for any swimmer, but get real. Nobody can swim like a fish-not even close.
A sailfish can go as fast as 68 miles per hour. That's pretty fast, even for a car. In comparison, a world-record freestyle swimmer crawls along at barely five miles per hour. Even an 11-inch Missouri rainbow trout can swim faster!
Fish are built for getting around in water, while people seem to be built for making big splashes when they cannonball off the high dive. Most fish are shaped like a football or a torpedo. This streamlined shape makes it easier for them to move through water.
Have you ever tried to run along the bottom of the swimming pool? Didn't it seem like you were moving in slow motion? That's because water is 800 times denser than air. It's the high density of the water that slows you down.
Water density is an advantage to a fish, however, because it helps hold it off the bottom. A largemouth bass can float around a pond the way a blimp floats in the sky. A fish in the water can use its energy to go places, but a person in the water uses a lot of energy just to keep from sinking.
Fish may be up to 80 percent muscle. The best arm wrestler in your neighborhood probably has a bulge like a tennis ball in his or her upper arm. A fish's bulging muscles are packed along its sides. That's where a fish gets most of its swimming power.
Fish muscles are different from people muscles.
Next time you're around someone that is filleting the catch of the day, sneak a peak at the fish meat before it is battered and fried. Fish muscles look like sideways W's stacked inside each other. These W's are called myomeres (my-oh-mears).
When a largemouth bass wants to move forward, it begins a side-to-side wiggle that starts at its front and moves to its back. As this wiggle goes backward, the fish goes forward.
The wiggle starts when the myomeres behind the fish's head on one side pull themselves shorter, and then the myomeres on the other side pull themselves shorter. Like football fans doing the wave cheer, these muscle contractions progress from side to side toward the back of the fish, and end with the flip of the fish's tail.
A fish's tail fin is an extension of the fish's body, much like the swim flippers you wear in the pool. Some fish are like eels and get more propulsion from their wiggling body. Others get more push from their tail. Some fish tails are floppy and full and are great for a quick burst of speed. Missouri's muskie is built like this. Other fish tails are stiff and crescent-shaped and are good for attaining high speeds over long distances. A tuna has a big C-shaped tail and can swim up to 44 miles per hour.
Big fish usually swim faster than little fish. The biggest and fastest swimmers in the fish world live in the open ocean where they can chase and catch food with less chance of crashing into something.
Not all fish swim the same way. Most fish use their pectoral and pelvic fins, which are located along their sides, to steer or maneuver. These fins act as brakes or rudders to help the fish stop, turn or go up or down or, in some cases, backward. Some fish rely on these or other fins rather than body movements to propel themselves forward part of the time.
These fish usually aren't very fast. However, they are well adapted for moving in and out of tight places to catch food or to escape from other fish that want to eat them. Their ability to maneuver helps them survive.
Missouri's bowfin can send waves along the dorsal fin (on its back) to move forward or to back into tight spots.
Of course, all fish are better swimmers than people. That's to be expected since they were born in the water and get to practice swimming every day. But if you put a fish on dry land, I'll bet a nickel you can outrun it every time!
