Blennioids are an order from the large group of perch-like relatives and thus belong to the series of bony fishes. Blenniiformes are usually small, slender, and have a body that is either unscaled or only partially scaled. Their skin has a high density of mucus-producing cells. A distinguishing characteristic compared to similar orders of bony fishes is their fused dorsal fin.
Almost all species of blennioids live in the sea, often found near the coast. Additionally, they are commonly found around rocky and coral reefs.
