Here is a picture of a BG fingerling beside a GSF fingerling for comparison caught in the same minnow trap at the same time.
BG and GSF fingerlings A little hard to tell in this picture but once you have seen a few of each fingerling fish the large mouth size of the GSF sticks out like a sore thumb. Usually green bars on the cheeks below the eyes, white or reddish tips on the fins, a more longish (rather than tall like BG)shape and the translucent colored border on the ear tab (as opposed to a more solid color in a RES with no colored border on a BG) are other GSF giveaways in the ID process.
Hope this helps. Likely not what you wanted to hear though.
