Do they have access to your inlet? If they can find moving water and gravel bottom you may not need to do anything.
Yes, I could add suitable gravel to the current at the head of this. Could add a mesh barrier in early spring if necessary to prevent predation of the fry to some extent if that makes sense to do? I figured the adults might clean out any that hatch without it? I like the idea of not doing anything. It's a specialty of mine... I'm pretty gifted in it actually...