Well they sort of are a big deal haha. They will greatly reduce the numbers of some native fishes (mostly darters since they would be direct competition), concentrate contaminants absorbed by zebra/quagga mussels (which then accumulates in the fish that eat the gobies), and they can harbour strains of botulism normally not available in the environment (which could cause waterfowl die-offs). But they do make a plentiful food source for bass, walleye, pike, trout, loons, cormorants, and other stuff that like to eat small fish.