Adjusting the Strength of an Animation

I have a simple looping animation of a fish moving its tail back and forth. Is there a way I can subdue the animation so that the tail doesn't flap as widely when the fish is idle? And I like it to flap to full strength when the fish speeds forward.

Basically, I want to take a looping animation and tell it to play at 10%, 20%, ... 100% strength. Is there a dynamic way to do this, without having to create individual animations for each strength level?

Thanks, this one's had me puzzled for a while.

 

http://unity3d.com/support/documentation/ScriptReference/AnimationState.html

 

Yeah, I'm aware of that page and am familiar with a handful of animation functions, but I just don't see how the pieces fit together to accomplish the effect.

I thought animation.weight would work, but it doesn't seem to have any effect, or I'm using it incorrectly. Blend seems to be appropriate for combining two animations, but I'm talking about using one. If someone could give me a quickie example, that would help a lot!