How Fish Swim

Swimming With The Fishes

Not in a “Sopranos” kind of way, but for real. When we sink below the surface of the tepid Pacific waters, a whole world unfolds before us. Like an aquatic ballet, millions of fish in a rainbow of colors zip to and fro turning on a dime at the command of their alpha fish or dodging a predator’s dark shadow. These animals are magical, a constant source of enjoyment … from a glass-bottomed boat, behind an aquarium window, or within an arms length while snorkeling or diving. Their magic deserves a closer look. 

Mr. Wizard Chimes In

For the record, there are some 25,000 known species of fish. And, they all fall into one of three categories – the jawless, the cartilaginous, and the bony fish. An example of the first group, the most primitive of the lot dating back some 500 million years, is the lamprey. Among the cartilaginous ones are the sharks and skates that only came onto the scene 400 million years ago. They don’t have bones only a cartilage skeleton thus the easier on the diner. They do, however, have nasty teeth and can be a tad unfriendly if provoked. And the last group, though bony, has the long-envied, oft lusted-after swim bladder. See what evolution gets you! They count among them some 20,000 of the known species therefore representing the most numerous. You’ve got your eels, catfish, salmon, perch, pike, herring, even seahorses among the bony group so they’re virtually everywhere.

Let’s Do Some Dissecting

To discover exactly how fish … ahem … swim, let’s look at their anatomy. As with people, the sleek and trim among the school move through their obstacles with ease. The density of the water impedes forward movement so Mother Nature designed fish to be slim and slimy. Your fast swimmers actually flex their muscles one side then the next to wriggle merrily along rather like a snake in the grass. Large tail fins add a bit of a kick to the forward movement while the body fins serve as stabilizers. These body fins can also lie flat against the fish’s torso to further streamline its profile.

Now some fish sorta row themselves along with fluttery pectorals, deprived of all other means of propulsion. A good example of this is the adorable seahorse, one of the sea’s most lovable creatures (ruling out the other all time favorite, the sea slug). Flying fish sport pecs that have evolved into wings that help propel them across the waves when escaping from someone wanting to eat them. Rays themselves have large and very powerful pectoral fins that also resemble wings to let them glide along almost effortlessly. They are truly poetry in motion.          

How Fish Float

Well, that’s pretty tricky. Many fish actually sink, which is dicey for those who aren’t bottom fish. This is exactly why sharks swim tilted upward, to combat gravity not just to see if you’re watching from above. Their oily livers and light-as-a-feather skeletons help them stay afloat. Then you’ve your pike that’s developed a different solution to the problem – an inflatable gas bladder! You guessed it. By controlling the amount of gas in his bladder, he can float merrily along blissfully unaware of the scorn from his fellow pike who don’t dare suggest playing “pull the fin” if you know what I mean. Such is life.

Some Factoids To Remember 

·               A fish’s body temperature is consistent with the surrounding water temperature.

·               Swordfish have been known to swim 60 mph and can actually poke a hole in a wooden boat at that speed.

·               Some catfish in Africa actually swim upside down enabling them to skim the water’s surface with their opened mouth in search of a good meal.

·               There are flatfish that actually propel themselves along by gasping in huge mouthfuls of water then squirting them out through their gills with such force it reminds us of a sort of liquid jet engine or aquatic SuperSoaker.

Well, all this matters not to those of us simply looking for a delicious, delicately poached piece of fresh fish dressed with a delightful white wine and lemon froth. We’re quite happy, in fact, that someone was cagey enough to outsmart the little buggers and catch them for our supper. Sorry as that may be we are, after all, thankfully higher on the food chain.