Sea robins, Prionotus tribulus, have heavily armored, spiny heads. They are capable of producing a grunting noise that can add to the fierce appearance of this unusual fish. Sea robins are bottom dwellers. They have separate rays (like soft spines) on their bellies, near the pectoral fins, that work like fingers. The rays help the fish find food buried in the sediment below. This fish’s head appears to take up about one third of its entire body length, hence its name. Big head sea robins inhabit bays and estuaries.