Why look up in the trees? If they are swimming just use a dip net.We normally have plenty of them but there have been years where there are massive die offs and reports of huge migrations to different locations where people have spotted them in large numbers swimming across the lake. I don't know what is going on with your area . If you are sure that that their food supply is still available, they should be there. I have had my best luck at first light . They usually get out and get eating and you can hear them cutting nuts. A good stand of hickory or oak trees is always my go to locations. Good luck! It can be frustrating. Ask around in your area.