Zoo plankton often rise up towards the surface at sunset
[url]https://en.wikipedia.org/wiki/Daphnia[/url]
Daphnia are diurnal and rise up towards the surface when it gets darker outside and sink down into the depths with increased sunlight. This rising and sinking happens all the time and coincides with the rising sun and setting sun.
Maybe the smaller fish are chasing these small zoo plankton organisms near the surface and that is what you are seeing.
I have no clue as to what species of fish you are seeing. Without capturing them and giving them a through examination and counting the number of scales along their lateral line or the number of fins on their body or the shape of the mouth or looking to see if there are any teeth on the tongue can one truly identify a fish species. This I leave up to the fishery management guys. I took a course in this while in college but didn't really like memorizing all the Latin Names of all the various fish species at that time. Guess I should have taken Latin in High School instead of Spanish. Many things in science are based on Latin Terms still.