My bad.... juvie herring!
Very well could be in your case, Sean. Usually happens after a good rain when fresh water discharge is higher in most ponds and streams.
But I still think pond herring are still too small to exit just yet. From mine experience, herring start dropping their eggs around the third week in April wouldn't be that size at the end of May.
You really have to be quite the expert in identify them properly. Many of all baitfish characteristics are still underdeveloped to make a very positive ID this early.