Yes, Niagara Falls is a barrier to fish movement. The falls create a significant vertical drop, making it impossible for fish to swim upstream. This has resulted in the separation of fish populations above and below the falls. As a result, distinct fish communities have evolved on either side of the falls, with some species found only above and others only below the falls. For instance, lake sturgeon, muskellunge, and walleye are found only in the upper Niagara River, while species like smallmouth bass, northern pike, and channel catfish are found only in the lower river.