Q: Can a youtube channel use my photography without permission under fair use?

A: Based on the limited amount of information you've provided, it does not appear that the infringing party has a strong fair use claim. However, determining whether "use" qualifies as "fair use" is a very fact-dependent assessment, and only a court can make this determination.

If you've already registered the images with the U.S. Copyright office for copyright protection, reach out to 2-3 attorneys and see if one you'd be willing to work with will contact the infringing party on your behalf. A law firm's letterhead on your demand letter may make the infringing party think twice before ignoring or attempting to dismiss your claims. Removing a watermark from an image and reusing it without permission is great evidence for willful infringement, which generally increases statutory awards if the claim proceeds to federal court.

Alternatively, Youtube has a copyright strike system. You may submit an infringement notice to Youtube requesting that the video is either (1) taken down or (2) ad revenue is redirected to you.

If you did not file for copyright protection, your images are still protected, but you're generally entitled to less damages if the claim proceeds to federal court. Registering your images with the U.S. Copyright Office before infringement (or within 3 months of the creation of the image) also allows an attorney to recover their fees from the infringing party (not from you). Without registration, an attorney is more likely to seek payment upfront, from you, before assisting with an infringement claim. So, if you haven't registered the images, it may make more economical sense for you to try pursuing this action through Youtube, on your own, first.