Swarm of fish - advice

I've been beach spinning lure fishing about 15 times now and I've still to
catch anything.

Last night just as it was getting dark, I saw fish for the first time! - a
whole shoal load of nippers jumping about on the surface of the fairly flat
sea in a swarm between 10 and 50 yards out.

I couldn't really see how big they all were, or even what type of fish they
were, but I could see that many of them were very small (fry).

If in future I see a similar sight - what would people recommend? To leave
them alone, that there might not be any big ones amongst them to catch?

Or that lure fishing is the wrong approach to take in that scenario?

As they were moving at a fairly fast pace to the right along the coast, I
had minimal time to react, so all I could think of was to swap my heavier,
bigger lure for a smaller floating, pike-type plug that would float stay
higher up in the water where they were.

Needless to say, I didn't catch any, but, given the chance again, I don't
want to miss out on other bigger fish swimming near them (although any size
fish is good enough for me!).

So, what would you have done in this situation?

Thanks for any advice.