Hardyhead Silverside (Atherinomorus lacunosus) ヤクシマイワシ – size 25cm
I think that these are Hardyhead Silversides. There are several similar fish, and it is hard to tell which are which. There were also some schools of Herklotsichthys quadrimaculatus in the same area at the time. Amami 2025
More Hardyhead Silversides which are a type of mullet. If I could see where the pectoral fins are I would be more sure of the identification. Amami 2025