Here's my thoughts...don't automatically assume oxygen depletion. Typical oxygen depletions cause larger kills than one or two fish at a time. Eliminate oxygen as a source problem by checking it several times daily, for a couple of weeks. I'll bet you'll see oxygen is fine. While you are evaluating oxygen, look for other stressors, such as ammonia. Find other trout pay lakes, talk with your fish supplier, analyze your water more intently. Then, take all that information, interpret. Compare what you have with "optimum", based on science and experience of others in the business. Then, you can begin to pinpoint the problem. If your water checks out, then start looking at your fish. You may want to switch suppliers or species, or sizes of fish. Or, you may decide to add more fish, and aerate, to increase competition.
I know this...all fish won't bite. Even though your inventory says you have "x" numbers of fish, you may not have what you think. Most pay lake operators have a game plan to remove fish from time to time, to replace with newer fish, increasing bite rates, thus increasing revenues, thus increasing cash flow, thus increasing wife approval (the most important of all).


Teach a man to grow fish...
He can teach to catch fish...