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The Smalltooth Sawfish

The world's living fishes (superclass Pisces) are divided into two categories: those whose skeletal structure is made of cartilage (the class Chondrichthyes); or of bone (the class Osteichthyes). The smalltooth sawfish (Pristis pectinata) belongs to the former, which includes the chimaeras, sharks, skates and rays, and is one of the nearly 1000 known species making up this class. There are, in comparison, over 24 000 species of bony fishes. A further taxonomic breakdown classifies the sawfishes as a type of ray (order Rajiformes) within the larger subclass Elasmobranchii (i.e., the sharks and rays, or elasmobranchs).

While sawfishes may be rays, their appearance is clearly more shark-like. They are easily characterized by their long, flat, snout or rostrum - sometimes making up as much as one-quarter of their total body length and embedded with sharp, tooth-like, scales along both edges. This is used to locate or kill prey (fish and invertebrates) and as a defensive weapon. Currently, there are considered to be seven species of sawfish though taxonomic uncertainties remain and this number may eventually be revised downwards. In general, they are found along many of the tropical and sub-tropical seas of the world, typically in the bottom, shallow, waters of bays and estuaries, though also, for some species, in rivers and lakes.

The smalltooth sawfish, itself, is also widely distributed and, besides the southeastern U.S., is found in the Caribbean and Central America and along South America to mid-Brazil, possibly the Mediterranean Sea, along African coasts, and in the western Indo-Pacific, perhaps as far east as the Philippines and Australia. The species can attain lengths of about 20 feet and weigh close to a ton, and likely lives for well over 20 years. Sexual maturity is attained only after about ten years with reproduction then occurring approximately every two years. However, much of the life history aspects and population dynamics of the smalltooth sawfish remain obscure.

The Problem

• The smalltooth sawfish was considered common in U.S. waters and, historically, was found throughout coastal areas of the Gulf of Mexico, Florida, and seasonally along the Atlantic seaboard to at least Cape Hatteras. In the Indian River, for example, the species was once so abundant that some 300 were caught by a single fisherman in one season during the late 1800s. It has since been extirpated from the Indian River and, indeed, impacts over the past century have been so severe that it appears that the species in the U.S. is now restricted to only the remote areas of southern Florida.
• Concern from scientists and conservation organizations ultimately prompted the U.S. National Marine Fisheries Service (NMFS) to review the status of the smalltooth sawfish and, on April 16, 2001, the agency published a proposed rule to list this species as endangered under the Endangered Species Act. On April 1, 2003, NMFS listed the U.S. population of smalltooth sawfish as an endangered species. The smalltooth sawfish has already been classified (1996) as globally endangered by the World Conservation Union.
• While there are many uncertainties, a recent study concluded that even under effective conservation conditions the recovery of the smalltooth sawfish "to a level where extinction risk is low will take decades, while recovery to or pre-European settlement would possibly take centuries."

The Causes

• The primary cause of the decline of smalltooth sawfish in the U.S. has been entanglement in commercial fishing nets (e.g., gillnets, seines, otter trawls). The toothy rostrum of the sawfish can cause extensive net damage and, consequently, fishermen tended to regard the species as a nuisance. It appears that many sawfish were killed immediately after being landed; those that were released alive were likely to have been severely wounded, either from the entangling or disentangling process or from removal of their "saw".
• The substantial changes to many U.S. coastal environments over the past decades are also considered to be a factor - though to an unknown degree. There have been severe losses in wetlands, extensive hydrological changes (such as in the Everglades), and increases in eutrophication, hypoxia, siltation and water turbidity throughout much of original sawfish habitat. Environmental pollutants, such as pesticides and industrial by-products, may also have had an effect.

The Context

• The smalltooth sawfish has been extirpated or nearly extirpated over large areas of its historical range along the coastal Atlantic Ocean and Mediterranean Sea. It is expected that the situation is similar over other areas as well (i.e., the Indo-Pacific and the east and west coasts of Africa), but little information is available.
• While the elasmobranchs as a whole have been severely impacted by fisheries - either as direct targets or as incidental bycatch - sawfishes and skates have been particularly affected. For some species, such as the smalltooth, common, and largetooth sawfishes or the thorny, common, and barndoor skates, global extinction looms as a possibility.
• The world's commercial fisheries, including those operating from the U.S., continue to have a profound impact on marine habitats, species, and food webs. They are considered by the U.S. National Research Council, for example, to be one of the activities most severely affecting marine biodiversity.

Further Reading

Carlson, J.K. et al.  2007.  Monitoring the recovery of smalltooth sawfish, Pristis pectinata, using standardized relative indices of abundance.  Biological Conservation 136(2): 195-202.

Martin, R.A.  2005.  Conservation of freshwater and euryhaline elasmobranchs: a review.  Journal of the Marine Biological Association of the United Kingdom 85(5):  1049-1073.

Musick, J.A. et al.  2000.  Marine, estuarine, and diadromous fish stocks at risk of extinction in North America (exclusive of Pacific salmonids).  Fisheries 25(11): 6-30.

National Marine Fisheries Service.  2006.  Recovery Plan for Smalltooth Sawfish (Pristis pectinata).  Prepared by the Smalltooth Sawfish Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland.

Seitz, J.C. and Poulakis, G.R.  2006.  Anthropogenic effects on the smalltooth sawfish (Pristis pectinata) in the United States.  Marine Pollution Bulletin 52(11): 1533-1540.

Simpfendorfer, C.A.  2000.  Predicting population recovery rates for endangered western Atlantic sawfishes using demographic analysis.  Environmental Biology of Fishes 58: 371-377.

Simpfendorfer, C.A.  2005.  Threatened fishes of the world: Pristis pectinata Latham, 1794 (Pristidae).  Environmental Biology of Fishes 73(1): 20.

Stevens, J.D. et al.  2000.  The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems.  ICES Journal of Marine Science 57: 476-494.