It is blue back herring, which is migrating bait fish in Hudson river. It is the most important bait for game fishes including Striped Bass. Because they are so abundant, we can easily catch them with casting net at the shore. Or we use Sabiki rig which is am imitation of small shrimp. I caught this one with the Sabiki rig. It is very easy to catch and fun. So, you can see many kids do herring fishing at the shore during May and June.
When I caught herring first time, I was surprised by its size. It was bigger than I though; its average size is 7 to 8 inches. People use them as a live bait for striper fishing. I tried it several times, but it wasn't so successful for me. I prefer lure fishing for striper.