Do I need to renew my iPhone developer account annually for my my app to continue being listed in the app store?
This is answered in the developer programs documents as well as the developer support section.
But to save you a trip:
Yes. If you don't renew your subscription your Apps will be removed from the search results and no longer be available for purchase.
What happens if I do not renew my membership?
If your iOS Developer Program membership expires, your apps will no longer be available on the App Store and you will not be able to submit new apps or updates. You will lose access to pre-release software, the Apple Developer Forums, Certificates, Identifiers & Profiles, and Technical Support Incidents. However, you will still have access to iTunes Connect and free development resources.