When I was kid, swimming in an Iowa lake, we would occasional a dense
ball of inch and a half bullheads, catfish they are. Two foot diameter
roughly a ball. So when I read a reference to a bait ball I knew what
it was like.

They showed one on 'animal snuff'. The tuna showed up and it was gone
in two and a half hours.

Someone gave us a ball of leopard frog tadpoles: one sweep of the net.
Papa was watching them. We dumped them in water too shallow for the
bass. We already had leopard frogs. so they will be OK maybe,but
without father to protect them from the other frogs.

So why do fish form dense balls? So an orca can eat them all real
fast?

Casady