Knifetooth sawfish

The breeding behavior of the Narrow Sawfish has been little studied. Fertilization is internal, and a number of young develop at one time in the oviduct, each one being nourished from a yolk sac.[4] Mating season varies by geographic region, and pups are born after a gestational period of about five months.[4][3] Litter sizes range from  6 to 23 pups with an average of 12. The pups are usually 43 – 61 cm long at birth, and their rostral teeth are not fully developed, being covered by a membrane, which prevents them from damaging the mother's tissues.[4]

Only two studies have been conducted on the age and growth of the narrow sawfish. The longest lived narrow sawfish found was 9 years old. However, the theoretical longevity is calculated to be 27 years. Females begin to mature at 8 feet 1 inch total length and are fully mature at 15 feet 5 inches. Males are fully mature at 8 feet total length.[3]

The narrow sawfish is docile towards humans and not large enough to consider them as prey. If left undisturbed, it is harmless towards people. However, when highly stressed, such as when caught in a net, narrow sawfish will flail their heads from side to side to defend themselves. This can potentially inflict serious injury on unprotected persons who get too close.[4]

The narrow sawfish feeds on small fish, squid, and invertebrates such as crabs and shrimp. It uses its rostrum in a side-to-side thrashing action to stir up the sediment and uncover concealed prey. It can also use its rostrum among schools of fish to incapacitate or stun individual fish. The head and rostrum of the sawfish contain thousands of electroreception organs called ampullae of lorenzini, which allow it to sense and locate the electric fields of its prey. The narrow sawfish is itself prey to various sharks such as the hammerhead shark (Sphyrna spp.), the bull shark (Carcharhinus leucas) and the copper shark (Carcharhinus brachyurus) and also the saltwater crocodile (Crocodylus porosus).[4]

Human actions are the main cause of the declining Narrow Sawfish populations and ranges. Overutilization, primarily from commercial fisheries, is its biggest threat.[3] Narrow Sawfish populations have likely decreased between 50 and 70% over the last 20 years. The Narrow Sawfish is a high-value target for fishermen. Sawfish are commonly hunted to make shark fin soup or for their rostrums to be displayed as trophies. Most countries have regulations against catching it; however, illegal, unreported, and unregulated fishing remains a threat. Furthermore, the Narrow Sawfish is a common bycatch for fisheries in its geographic range. The toothed rostrum makes it vulnerable to most types of fishing gear, particularly nets. Damaged, neglected, or lost fishing gear (aka ghost nets) are also a considerable threat to Narrow Sawfish. Pregnant females and juveniles are at the highest risk for this threat. Additionally, the Narrow Sawfish has the highest post-release mortality of any sawfish species.[10]

Habitat loss and water pollution are also threats to the Narrow Sawfish. Coastal development, coastline urbanisation, and an expanding mining industry result in the modification and destruction of critical habitat. Furthermore, the pollution from these activities degrades the water quality. The Narrow Sawfish range is suspected to have declined by 30% from historic extent. These threats are expected to become more significant as the human population grows.

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Natural threats, such as disease and predation, do not significantly harm the Narrow Sawfish population.[3]

The IUCN listed the Narrow Sawfish as "Endangered" in its Red List of Threatened Species in the year 2000. This was due to the threats of overutilization, habitat loss, and a decreasing population. Its status was updated to “Critically Endangered” in 2006. In 2013, its status returned to “Endangered” due to the availability of new information.[10]

On September 10, 2010, WildEarth Guardians petitioned the US National Marine Fisheries Service (NMFS) to list six sawfish species - the Narrow Sawfish; the Dwarf Sawfish, the Freshwater Sawfish, the Common Sawfish, the Narrowsnout Sawfish, and the Smalltooth Sawfish - as endangered or threatened under the Endangered Species Act.[11] The NMFS published a 90-day review on March 7, 2011, stating that action may be warranted for five of the six species. Information available at the time indicated that the Common Sawfish was not a valid species.[12] On June 4, 2013, the NMFS published a proposal that concluded all five Sawfish species were at high risk for extinction. The proposal listed habitat loss, water quality, and overutilization as the biggest threats to the Narrow Sawfish.[8] The NMFS published its final ruling on December 12, 2014, which listed all five Sawfish species as endangered. Scientific data showed that geographical areas occupied by the Narrow Sawfish were entirely outside U.S. jurisdiction. Therefore, the NMFS was not able to designate any critical habitat. Furthermore, the NMFS did not develop a recovery plan because they would not be able to enforce it.[10]

Western Australia and Queensland have listed protections for the Narrow Sawfish as a “no-take” species. Sawfish also are considered “no-take” species in India, but the legislation is frequently ignored and rarely enforced. International trade of the narrow sawfish has been banned by its inclusion in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix 1.[9]

Current population of the Narrow Sawfish is unknown.[9]