👉 Clupeoids are a group of small, hard-bodied fish that have two pairs of large, soft, flattened appendages called pectoral fins. These fins are used for swimming and maneuvering in water. Clupeoid fish also have a distinctive type of gills known as "clupeoidal gills" which provide the fish with a high surface area-to-volume ratio to improve their efficiency at extracting oxygen from the water. Clupeoids can be found in many different environments, including rivers
