Daily Science Dose

Can fish be said to have a gait? I think it’s a cute way to look at things. There are several methods that fishes use to get around, separated by Charles Breder in 1926 into three motion types: Anguilliform, Carangiform, and Ostraciiform.

Now, before I tell you about these forms, and about the various forces involved in fish locomotion, you’re probably wondering why I care about such things.

Okay, maybe you’ve got that one figured out. But why now? Why here?

Take a look at my fish:

He’s having some trouble getting around. I’m not sure exactly why. He got better for 1.5 days, and has now returned to his corkscrewing state. He’s much more mellow now in his corkscrewing, probably due to exhaustion.

His problem (I’m thinking it must be neurological) and his crazy swimming made me wonder…what’s awry here? Pitch? Roll? Yaw? What are those things again?

Pitch, roll, and yaw are various forces that can act on a fish’s body while in the water. I suppose we can also be affected by pitch, roll, and yaw, so you’d better listen up!

Pitch is the body moving on the vertical plane. Imagine it this way - a fish is looking down at the bottom of the tank, you tell him to look up, and he brings his head and body up in a backward arc until his head is facing the water.

Man. I’m so terrible with the 3D. Tell you what. I’ll have my artist friend draw a picture of a fish and the various forces. Until then, you’re stuck with my imaginary scenarios.

Pitch. If a fish was, say, stuck in this pitch, he/she would be doing somersaults.

Next, we have roll. This one is easy to explain. Imagine a hot dog at 7-11. Mmm. See it glistening as it spins on those metal rollers which ensure that the hot dog is cooked evenly all around?

Now imagine that the hot dog is a fish. See him spinning? Turning, turning. Rolling, rolling. That’s roll.

Next, imagine the fish turning back into a hot dog, and then imagine eating it, if you’re into that sort of thing.

Finally, we’re left with yaw. Yaw is the fish moving in the horizontal plane. An example would be the fish moving his head from side to side, shaking his head to say, “No, do not think of me as a hot dog, do not imagine me roasting at 7-11.”

Again, a picture of this would be worth at least 500 words, and will be coming shortly.

So, pitch, roll, yaw. Pitch is fish looking up, or perhaps the fish saying yes; roll is the fish at 7-11; and yaw is the fish saying, “No way.”

What do you think is going on with my fish? Clearly, he’s got some rolling action going on. But if you watch, his pitch and yaw are also off.

He’s a mess.

There are some more forces working on a fish. Those are drag, gravity, lift/buoyancy, and thrust. I’ll get to those when we have the drawing.

Okay, back to Breder’s three forms of fish motions.

Anguilliform - swimming while being able to bend into more than half of an S. Real bendy like. My dojo loaches swim in anguilliform-style.

Carangiform - the body bends into less than half of an S, and the movement comes mostly from the caudal region (more focused in the back when compared against the eel-like swimmers).

O, the caudal fin, just so you know, is that thing that mermaids like to walk around on. Or, people in mermaid costumes. It’s the tail end of the fish.

Ostraciiform - this one describes fishes like boxfish whose bodies are, more or less, inflexible. They’re not able to eel at all, and rely solely on the caudal fin. There’s more to their movement than just the caudal fin, but, for purposes of the three main categories, this is a good way to think of it. Let’s look at it from a caudal perspective.

These types of movements are further broken down…subcarangiform, labriform, etc., but…who wants to know about all that?

(If you want to know about all that, let me know, and I’ll pull out my vertebrate bio notes. We’ll have some more fun…talk tuna.)

That’s it for today. I’ve gotta get myself to Burbank and deliver 70 plus baby snails.

Have a good weekend! If you go swimming, or are playing with toys in the bathtub, think about pitch, roll, and yaw, won’t you?

pitch, roll, yaw, fish, locomotion, anguilliform, carangiform, ostraciiform, caudal, goldfish, corkscrew, swim, Charles Breder, 7-11, hotdog