The weird, wonderfully-designed sawfish

It is not hard to tell where the sawfish gets its name—the long snout (‘rostrum’) covered with tooth-like ‘denticles’ is one of its most distinctive features. And it is not only for show; it is a dangerous weapon, both to other fish and to fishermen who can be injured by a sawfish as it tries to resist being caught! In the same family as rays, there are approximately five living species of sawfish, all listed as endangered. They have been subject to overfishing, as their rostrums are both in demand as curios and used in traditional medicine. Their fins are also considered a delicacy. In addition, their habitat has been severely reduced (juveniles spend most of their time in shallow water bays and estuaries) and they are often accidentally caught, as their toothy snouts easily snag in fishing nets.

Sawfish can be found in the Atlantic, Pacific, and Indian oceans. The dwarf sawfish, Pristis clavata, only reaches about 1.5 m (5 feet) in length. The others are much larger, often reaching 7 m (23 feet).

Sawfish biology

Along with sharks and rays, sawfish belong to a class of animals called the Chondrichthyes (cartilaginous fishes). They are actually grouped with rays in superorder Batoidea and have several characteristics in common with them, including the fact that both the mouth and gills are on the bottom of the animal. The characteristic denticles on the sawfish’s rostrum are not true teeth, but modified scales—the sawfish does have teeth in its mouth.1 The rostrum has electrical and mechanical sensors that detect slight movements, allowing it to stalk prey in murky water.2 When it encounters something that seems tasty, it thrashes its rostrum about, stunning and/or wounding the prey. It can also use the rostrum to probe for shellfish in soft sand and mud, and it can temporarily pin fish to the bottom before sucking them into its mouth. The rostrum is also a defensive weapon against sharks.3

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Source: | Lita Cosner-Robert Carter