Is it cheap and easy for you to put in some FHMs now?

If so, the winter survivors will start spawning as soon as they are able in the spring.

If you are going to put in some Gambusia (mosquito fish), you might still be able to seine a few out of the remaining pools in a nearby creek. Same theory as the FHMs. The biggest caveat with that plan is that you must be 100% sure of all of the creek "minnows" that you are adding to your pond. Adult Gambusia are very easy to identify. You definitely do not want any misidentifications such that you might add anything (like GSF) that you will regret later.

Good luck on your new pond! I predict much fun for you this spring just WORKING on your pond.