Get a bad memory back on track here. I know there are both Tricos and Paraleps around at the same time and one mates in an east/west flying pattern while the other mates in an up and down dance. I believe tricos are east/west and paraleps are dancers, do I have that correct?
It's kinda funny in a sick sort of way when the mating swarms overlap. This happens frequently downstream of the gauging station (not the 10th St one) on the LL. There's mid-air collisions between the two groups, and if you're alert to this, you can take advantage of it - the fish do.