Here's the Animal Crossing New Horizons New Fish in September list. Bookmark this page to know the selling price, spawn location, shadow size and time to catch these new fish.
Walker Cicada is not an easy to catch bug in Animal Crossing: New Horizons, it is available only for few months and if you want to catch this bug then read this guide.
If you want to know how to catch a soft-shelled turtle in ACNH, then read this guide. Includes info about spawning conditions, timing, location and more.