IF the temperatures are below 0 dont bother with first light, because the river will be slushy and your line and guides will freeze like crazy. You can still catch fish but its alot harder to fish.
Yeah i kept a trout once from a naturally reproducing lake O trib and felt terrible, i can always buy trout or go to a stocked pond and get them there so why keep a naturallly reproducing fish? But if bass tasted good i wouldnt care about keeping them.
since your fish was pretty fresh....
take a chunk of skein and put it in a roe bag, if the eggs are whiteish when you tie the roe bag chuck the eggs their probably premature, and you should just chuckem