The river can be terraformed using the terraforming app and can be created by conjoining an end with the river mouth, or else it will be considered a pond. If you want to know when this type of fish can … Anyone who has played the game knows how immersive and fun the experience is to catch bugs and fishes. Many are leaving as well, so make sure you’ve grabbed them all. In New Horizons. River Mouth locations in Animal Crossing: New Horizons. A new month is just around the corner, which means it's your last chance to catch certain bugs, fish, and sea creatures in Animal Crossing: New Horizons. This is a list of all River fish found in Animal Crossing: New Horizons (ACNH) and how to find them. For Animal Crossing: New Horizons players this means there’s a ton of new creatures to track down and catch. The River Mouth in Animal Crossing: New Horizons is a special and very small location where any river meets the ocean. Animal Crossing NH: Where to Catch a Sturgeon in the River Mouth. In New Horizons, there are no fish that are exclusive to the river, however the extentions mouth and clifftop have fish that can only appear in said areas. And then on September 1st you’ll want to be sure to have this list handy so you can make sure you add all these creatures to your museum. Animal Crossing: New Horizons has a wide range of exciting features that closely represent the real world. For Animal Crossing: New Horizons on the Nintendo Switch, a GameFAQs message board topic titled "Does terraforming allow you to completely close rivers create new river? The easiest ways to find one are by following the coast of your island, or by finding a river and following it … ".