I fished the incoming tide yesterday and as I approached the beach I could see surface activity that brought a smile to my face. Over the last week, the few times I witnessed surface activity were quickly rewarded with a cutthroat within one or two casts. I tied on my trusty surf candy and quickly realized these fish wanted nothing to do with my offering. I peered into the water and my usual bait fish were around in addition to an incredible population of clear 2cm euphausiids. I resorted to watching the spectacle without participating. From what I could determine, the feeding fish bulging at the surface were around six inches or slightly larger. Occasionally I'd see one near me rise quickly, feed and return to the depths. I'm embarrassed to ask, but being new to the salt I'll swallow my pride. What's the differential diagnosis (and age) for surface feeding fish of that size in this situation?