Absolutely, you can catch smallmouth bass with topwater lures in a large river system even when the water temperature is around 54 degrees Fahrenheit. Although topwater fishing is generally more productive in warmer water, smallmouth bass can still be quite active and responsive to surface lures in water temperatures in the mid-50s.
When fishing in these conditions, it's beneficial to focus on areas where the water might be slightly warmer, such as near warm water discharges or in shallow, sunlit areas during the warmer parts of the day. Also, consider using topwater lures that create a bit more disturbance, like a buzzbait or a walking bait, which can be effective in attracting attention in cooler water.
It's important to adjust your retrieve speed as well. In cooler temperatures, bass are typically less aggressive, so a slower, more deliberate retrieve might be necessary to entice a strike. Experiment with pauses and varied speeds to see what triggers a response from the fish.
In summary, while topwater fishing in 54-degree water can be challenging, it's certainly possible to have successful outings with the right approach and lure selection. Keep an eye on the conditions and adjust your tactics accordingly to increase your chances of landing those aggressive smallmouth bass.