Thanks db for the link. I went back to the search page and figured out what I did wrong so as not to get that thread as a result. Won't be making that mistake again.

Really sorry to hear they are in the Q. I was poking around on the web trying to find confirmed info about their natural predators. I came across a paper [   (You need to Login or Register ] about research in Lake Maggiore (Italy) where they are native and which has experienced a huge population growth. About halfway in, there starts discussion of parthogenic females overwintering (something apparently not seen historically). Overall, the paper seems to be saying that the population growth is tied to warming of the lake. This isn't my field, but I looked up a lot of words and tried to remember the definitions long enough to return to the text. 

About the predators...apparently in Lake Maggiore, it is the coregonids that feed (or did feed, since their population decreased after a few years of warmer water in their typical layer and, I guess, pollution or acidification). I looked that up and it is Whitefish. Obviously, the european whitefish and the N. American are long separated, but, is there any evidence that Whitefish have been eating the spiny water fleas? And, if I were a more agile statistician and had more time, I might be downloading lake temperatures and seeing if there were any correlation to rise in spiny water flea population.

And, old_salt, yeah, count me in on being an invasive, too.  :-/