Zebra mussels will create fish habitat and destroy prey at the same time. The prey that is destroyed (like shad) will be replaced by prey that can live on the bottom. Yes, with a zebra mussel cluttered bottom, that will be good for crayfish. That is where the nutrients will be and the zebras will also provide some shelter. Zebra mussels will also become food. There will always be fish to catch, but the type of fish we catch will most liekley shift.
The predators will for sure eat the zebra mussels, but what we have learned about these mussels is that predation does not keep up with their spread. Once they get a strong foothold, they will reproduce exponentially despite predation.
Guides always tell us to follow the bait. What if the bait is gone? Then what? The ecosystem will get shaken up. The food chain will scramble, and their will be winners and losers. Winners will be animals that can adapt to bottom living. Pelagic fish will most likely be losers unless they adjust to new food sources which will create competition between species that does not occur now. It is a night mare for the ecosystem, but I agree that it will be hard to predict exactly what will happen.
This is what happened with the Hudson River.
"While the mussel's initial impacts weren't a surprise (phytoplankton also crashed in the Great Lakes), the researchers couldn't anticipate exactly how the river's complex web of life would respond. The monitoring revealed a dynamic series of shifts.
After the invasion, the team noticed that growth rates of open-water fish such as shad, herring, and striped bass dwindled in zebra-mussel infested areas. Many of these fish also appeared far from their usual habitats, moving downriver to mussel-free areas to seek food. (Zebra mussels cannot tolerate much salt, so they have not colonized the brackish estuary at the lower portions of the river near Yonkers and New York City.)
Shallow-water fish, however, benefited from the invasion. With fewer phytoplankton to cloud the water, the Hudson's murky brew became about 40 percent clearer. Light could then penetrate deeper and stimulate production of aquatic plants. Shallow-water fish that prefer weedy environs, such as sunfish and large- and small-mouth bass, actually found more vegetated habitat after the zebra mussel invasion. These fish species have grown larger and have expanded their territory. "With almost all invasion cases," says Stuart Findlay, "there are winners and there are losers.""
It makes sense that striped bass and white bass could struggle in zebra infested waters where bass and catfish may actually get their habitat expanded. I am not fearful that the fishery will go away, but it will definitely change. But that is not the major concern with zebra mussels. Our waterways are not fishing first. Zebras are not good for non fishing activities either.