while mothers return to the region where they were born to give birth to their own young. The length of the full lifespan of sawfish is labeled with considerable uncertainty. A green sawfish caught as a juvenile lived for 35 years in captivity, and a smalltooth sawfish lived for more than 42 years in captivity. In the narrow sawfish it has been estimated that the lifespan is about 9 years, and in the Pristis sawfish it has been estimated that it varies from about 30 to more than 50 years depending on the exact species. Electrolocation The rostrum (saw), unique among jawed fish, plays a significant role in both locating and capturing prey. The head and rostrum contain thousands of sensory organs, the ampullae of Lorenzini, that allow the sawfish to detect and monitor the movements of other organisms by measuring the electric fields they emit. Electroreception is found in all cartilaginous fishes and some bony fishes. In sawfish the sensory organs are packed most densely on the upper- and underside of the rostrum, varying in position and numbers depending on the species. Utilizing their saw as an extended sensing device, sawfish are able to examine their entire surroundings from a position close to the seafloor. It appears that sawfish can detect potential prey by electroreception from a distance of about . Some waters where sawfish live are very murky, limiting the possibility of hunting by sight. Feeding Sawfish are predators that feed on fish, crustaceans and molluscs. Old stories of sawfish attacking large prey such as whales and dolphins by cutting out pieces of flesh are now considered to be wholly unsubstantiated. Humans are far too large to be considered potential prey. In captivity they are typically fed ad libitum or in set amounts that (per week) equal 1–4% of the total weight of the sawfish, but there are indications that captives grow considerably faster than their wild counterparts. Exactly how they use their saw after the prey has been located has been debated, and some scholarship on the subject has been based on speculations rather than real observations. In 2012 it was shown that there are three primary techniques, informally called "saw in water", "saw on substrate" and "pin". If a prey item such as a fish is located in the open water, the sawfish uses the first method, making a rapid swipe at the prey with its