Welcome to PB posting.

I assume you decided not to kill off the pond and start over.
Assuming you ruled out that option then putting in the LMB will act as predation on the small catfish. Given those size fish I would add some advanced sized BG (over 5 inches) both male and female. Up to 100 would help. Adult RES would also be a good addition. You may need some structure to help the yoy BG. Be careful of adding low DO well water.