Without good data we are all just guessing. We need detailed info and pics with times , weights , lengths , species and ages would help. Catch data does not tell a lot about reproduction and yoy survival and small fish (minnows and forage) status so seine data would help. Visual info which we also don't have can add critical parts to the puzzle. Fertility is an open issue as is harvest data and its effects on total mortalities.

Adding structure is probably good but even that depends.

Best step is to get a pro to electrofish the pond and report. If that is not possible then develop the data and report back.