White sucker or aka common white sucker.
http://www.lakesuperiorstreams.org/understanding/whitesucker.htmlhttp://www.lakescientist.com/lake-facts/fish/white-sucker/The pond looks like it is a candidate for winterkill thus YP may be the only sport fish that will consistently survive there. Since you are on a limited budget I would buy a minnow trap, bait it, and set it and run it every day each time you are there.
If it were mine, and only YP are present, I would start by stocking some 8"-12" SMB or less preferable 8"-12" walleye (see later). SMB 6"-8" might work but this will be financially risky when money is limiting. If you have access to lake access and are a good angler, you could risk bucket stocking these predators. Larger SMB might be a little pricey, but I doubt smaller 3"-5" sized ones will survive in a stunted YP pond due to excess food competition and heavy losses will waste your money. Been there done that before.
By adding any predators you run the risk of loosing them to winterkill. YP tolerate lower DO than bass or walleye. Let the predators (preferably SMB (reproducing)) do their job until you see the average YP catch sizes increasing. Walleye won't reproduce; a negative in your case. You really want a moderate reproducing predator to gradually outcompete the YP. Reproducing LMB will reproduce too fast and overpower the pond to provide you with a new problem.
Then when YP sizes are increasing to numerous 8"-9"ers gradually start removing some SMB each year until you have a more stable balance of predator and prey ratio. You may have to wait to do all this when your budget is bigger and can stock enough SMB to fairly quickly impact the stunted YP fishery. It will likely take 15-25 SMB/ac to make a noticeable impact within 2-3 yrs.
Your white suckers could be spawning in the spring water area that enters the pond since the one you caught appears to be a youngster abt 8" long.
