I'm not much of a fisherman, but years ago when scouting a Murray River duck reserve/swamp in January prior to the season - Kataraptko - now a ffffing commie National Park - came repeatedly across masses of carp all thrashing in a large circle each time several metres wild and nothing but continual thrashing fish bodies.

Fashioned a home made spear from a knife.

A shotgun would have been better.

Explosives even better.

What were the carp doing? Spawning? Feeding?

The homemade spear didn't work well as the fish just slipped straight off it, unless the water was shallow enough to pin them to the swamp bed.