Human Influence on Sawfishes, by David Lewis

Just imagine watching a several-meter-long fish with a gigantic snout lined with jagged teeth on both sides of its snout.  This not a mythical creature form legend, and instead currently roams the oceans today.  Sawfishes are part of the Family Pristidae, a cartilaginous fish.  There are five different species of sawfishes that are recognized with the largetooth sawfish (Pristi pristi) and smalltooth (Pristi pectinata) being the most well-known. Sawfishes can typically be found in coastal tropical and subtropical regions along with some estuaries and river systems.

Sawfish in public aquarium.   Photo by Lorenzo Blangiardi  Creative Commons Flickr

They are named the sawfish because of the row of teeth that lie on each side of its long rostrum. Sawfishes use their “saw” for feeding on other fishes by swinging it from side-to-side to stun schools of fish making it easier for the sawfishes to eat them.  Typical prey of sawfishes are small fish, and prawns along with other crustaceans. In addition, they use their “saw” as a defense mechanism against predators, such as other sharks that want to eat them.  Recent studies have also shown sawfishes can use their rostrum to sense electric fields of prey. There are statistics that show sawfish populations have declined by as much as 99% in some cases, making them among some of the most endangered fish species in the world. Also, out of all the recognized species of sawfishes, all are listed as critically endangered on the International Union for Conservation of Nature and Natural Resources Red List. Sawfishes are very important from a cultural standpoint (McDavitt 2005). 

Many indigenous people around the planet consider these fishes symbolic icons that represent strength, admiration, and spirituality (McDavitt 2005).  In addition, some native aboriginal tribes in Australia believe that sawfishes are forms of supernatural beings that created the land and oceans, so they felt a connection between the land and the water (McDavitt 2005).  Other cultures, such as the local people living in the Bijagos Islands off the western coast of Africa, would use sawfishes as headdresses for ceremonial dances although wooden replicas of sawfishes are now being used due to the scarcity of sawfishes found (Leeney and Poncelet  2013).  The obvious question is then: Why are sawfish endangered? Not surprisingly, human influences greatly contribute to this unfortunate decline of sawfish populations.  Therefore, I will look into the effect of anthropogenic influence on sawfish populations.  More specifically, I will investigate some notable factors associated with anthropogenic influence and how this influence has adversely affected sawfish populations.  Specific factors attributed to this decrease in sawfish populations are overfishing, and habitat alteration.  People need to understand how to reduce if not eliminate these factors such that the planet does not lose a very interesting and culturally important fish.

One of the first factors to note that adversely affect the sawfish population is overfishing.  Overfishing has been the result of many people catching sawfishes via by-catch when people are catching large amounts of other fish species for harvest.  In addition, they are also purposely caught in some countries for meat, fins, and skin (used for leather). Importantly, since sawfishes mature relatively slowly and have a low fecundity, they are very susceptible to population decline due to overfishing. There was a study conducted about largetooth sawfish being sold in northern Brazil despite its policy that commercialization of largetooth sawfish is illegal to be marketed (Palmeira et al. 2013).  Researchers have specifically found that “fresh or salted fillets of this fish can be found in markets, labeled as ‘sharks’(Palmeira et al. 2013).”  According to a survey taken from the University of Florida, the largetooth sawfish species has been historically found from the Gulf of Mexico and southern Florida down to the coast off of south-central Brazil (Burgess et al.  2010).  The survey also showed that the number of sawfishes encountered has decreased in abundance with similar trends observed with smalltooth sawfish (Burgess et al. 2010).  With both species, the decline seen in these species is attributed to increased fishing pressure along with environmental changes (Burgess et al.  2010).  As shown by these journals, sawfish populations are decreasing and despite policies that are put in place (such as the policy in Brazil), these fish are still illegally harvested.

Display of marine curios includes sawfish bills.  photo from Florida Keys Public Library. Creative Commons Flickr

As if overfishing is not a bad enough issue causing the sawfish to be critically endangered, habitat degradation is another major issue that has contributed to their decline.  According to a study conducted in West Africa, sawfishes are very susceptible to habitat destruction because of their large size and their river habitats (Robillard and Seret  2006).  Specifically, these habitats make it easier for fisherman to find and capture sawfishes along with disrupting their habitat (Robillard and Seret  2006).  While this is a major problem for sawfish populations, multiple action programs were put in place by West Africa (Robillard and Seret  2006).  Interestingly, the countries that were visited for this study revealed that a sawfishes were highly demanded by Asian markets for the sawfish fins used in soups and Asian lobbyists prevented a project proposal to include the whole family of sawfishes from being protected (Robillard and Seret 2006).  This goes to show that money is ultimately the main driver for conservation, the expression, “fatter wallet” definitely comes into play. 

Ritual mask used during manhood ritual ceremonies in Guinea Bissau (Robillard and Seret 2006).

Overall, there are environmental policies put in place as the sawfishes are being put under the endangered species act (ESA) along with establishment of other local environmental programs in the hopes that these fishes will not become extinct from the planet.  However, money is the biggest driver in many decisions.  While the importance of conservation can be emphasized, such as how overfishing and habitat alteration can severely affect sawfish survival, it may or may not be enough to save them from extinction.  If people want to see and know about an interesting fish, serious protocols must be implemented or their existence will end and a fading knowledge will be the only thing left remaining of these fish.

References

Burgess, G.H., Carvalho, J.F., Imhoff, J.L. 2010. An Evaluation of the Status of the Largetooth Sawfish, Pristis perotteti, Based on Historic and Recent Distribution and Qualitative Observations of Abundance. Florida Museum of Natural History. Available: https://www.floridamuseum.ufl.edu/files/4814/1779/0135/ltsawfish_finalreport_2010.pdf

Kyne, P. 2014. Plundered for unique body parts, sawfish are on the brink. The Conversation.  Junw 8.  Available: https://theconversation.com/plundered-for-their-unique-body-parts-sawfish-are-on-the-brink-27743

Leeney, R.H. and Poncelet, P. 2013. Using fishers’ ecological knowledge to assess the status and cultural importance of sawfish in Guinea-Bissau. Aquatic Conservation: Marine and Freshwater Ecosystems 25: 411-430.  

McDavitt, M. T. 2005. The cultural significance of sharks and rays in Aboriginal societies across Australia's top end. Marine Education Society of Australasia. 5 pp. www.mesa.edu.au/seaweek2005/pdf_senior/is08.pdf

Palmeira, C.A.M., Rodrigues-Filho, L.F., Sales, B., Vallinoto, M., Schneider, H., and Sampaio, I.  2013. Commercialization of a critically endangered species (largetooth sawfish, Pristis perotteti) in fish markets of northern Brazil: Authenticity by DNA analysis. Food Control  34:249-252.

Robillard, M., and Seret, B. 2006. Cultural importance and decline of sawfish(Pristidae) population in West Africa. Cybium. 30:23-30.