Let me preface this by saying Small Samole Size error most likely BUT
IME, hydrilla did not hurt larger fish numbers. Maybe it would if it took over the lake totally, but with the water depths we have, Nope.
you might not be able to eliminate hydrilla with normal amounts of water fluctuations, but you certainly can control it. If you drop the lake 5 foot over the winter and a hard freeze occurs (we get a couple of those a year) all the exposed hydrilla dies and you get an inside edge (I love fishing that) AND if you put > 30 FOW on top of it, hydrilla dies back. Bull often sees Plus 20 above the old 654 number. So, if we ever got enough stability for hydrilla to get established, I still think it would be limited to a thinner band of water with a clean inside edge at 8 foot or and an outside edge at 15 FOW. Then we would have a 690 year and kill all of it.