Considering the high stress of the stocker fish it is surprising that any survived despite them swimming away. Chemical and temperature shock stress are difficult for most all fish to overcome in the long term. They can swim away but survival is usually very poor.
Most YP sink as they die. My pond of YP is old enough that I loose numerous old big YP each year. I rarely see dead ones floating. Also others with perch in my area rarely see dead perch unless the fish had eaten food or pellets that cause gas, bloating, and then floating. IMO dead YP with empty stomachs rarely float. YP almost always rest idle on the bottom at night, thus I don't think they have as much air bladder buoyancy as many other fish.
I would talk to your YP supplier to see if they won't replace the YP at cost or a significant discount. Try to get two sizes 2"-4" and 5"-6" to have fish to make up for a poor year class that you are likely to get in 2016.
Last edited by Bill Cody; 02/22/1607:57 PM.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management