Sawfish research in Mexico, Central and South America

By Ruth H. Leeney

Two sawfish species – the smalltooth and largetooth sawfishes (Pristis pectinata and P. pristis) – are known to have occurred historically in Caribbean and Central American (Atlantic) coastal seas, whilst only the largetooth sawfish is known from the eastern Pacific. The current status of sawfishes in the waters of Mexico, Central America and the west coast of South America is poorly understood. Until recently, little up-to-date information was available from these regions but happily, since 2014, numerous research projects have developed to address these data gaps. Many of these projects are multi-country collaborative efforts, which facilitates the sharing of resources and expertise. In my role as Sawfish Conservation Coordinator for the IUCN Shark Specialist Group, I recently compiled information about the sawfish research projects underway in Mexico, Mesoamerica and South America, and put the various researchers and teams involved in contact with each other where necessary. The information I received from teams working on sawfish projects is summarised below, but if you are working on sawfishes in these regions and don’t see your project mentioned here, please do get in touch!

Image from extremecoast.com

In Mexico, Océanos Vivientes AC is conducting a nationwide survey of historical and current presence of sawfishes, in order to evaluate the conservation status of sawfishes in Mexico. The team hopes to work towards a change in Mexican legislation relating to sawfishes. Océanos Vivientes is also collaborating with Conservation International to develop sawfish research in Colombia.

MarAlliance is working in Belize, Cuba, Guatemala, Honduras and on the Caribbean coast of Mexico. Their work on sawfishes is part of a broader programme which involves working closely with fishing communities to monitor marine megafauna, especially elasmobranchs. They hope to assess the current existence of sawfishes in each of their study regions, document historical occurrence, distribution and local uses of sawfishes, and identify strategies to encourage the recovery of any remaining sawfish populations.

A largetooth sawfish (c. 5.6 m total length) captured off northern Peru, and released alive, in
February 2015.

In Peru, Planeta Océano launched a sawfish research programme in early 2015, in collaboration with my organisation, Protect Africa's Sawfishes. This involved a short training programme covering aspects of sawfish ecology and conservation, as well as interview methods for assessing the status of sawfish populations. The training course attracted participants not only from Peru but also from Ecuador and Colombia. Following the training, course participants and Planeta Océano staff conducted interviews at numerous fishing ports and landings sites in northern Peru, and interviews will be conducted further south, later this year. Very recent captures of largetooth sawfish have occurred in northern Peru, including one adult caught and released alive in February 2015. Planeta Océano has also built collaborative links with teams in Ecuador, El Salvador and Costa Rica, supporting them to collect data on sawfishes using similar methods, and developing community awareness activities and educational materials on sawfishes, to be used throughout the region. Planeta Océanos’ collaborators at the Universidad Laica Eloy Alfaro de Manabí (Ecuador), led by Dr. Rigoberto Rosas-Luis, have already conducted 429 interviews with fishermen throughout Ecuador. The most recent capture of a sawfish there was in 2014, in San Lorenzo, northern Ecuador. 
 

Dr. Rosas-Luis interviewing fish vendors in northern Peru.

Fundación Talking Oceans and the Smithsonian Institution is conducting sawfish research in Costa Rica, Panama, Colombia and Ecuador. They aim to assess the current distribution and conservation status of sawfishes in the ETP, as part of a wider project to identify and map elasmobranch critical habitats and assess MPA effectiveness. Fundación Talking Oceans are working with a number of collaborators including Marviva, WWF, USAID-BIOREDD, Universidad de Costa Rica, Playa Tortuga, Malangwai, SINAC, PRETOMA, Universidad de Panama, ARAP, Planeta Océano and NAZCA. 

Juliana Lopez Angarita and a fisherman with a sawfish rostrum from a market in Costa Rica. Photograph (c) Alex Tilley.

Central and South America are also key regions for sawfish conservation for one particular reason – the cock-fighting industry. Cock-fighting is a very popular pastime in many Central and South American countries, and since the mid-1970s, sawfish rostral teeth have been the preferred source of ‘spurs’ – the sharp spikes which owners attach to the feet of their bird in order to inflict damage on the opponent. Concern has grown within the cock-fighting industry as sawfish rostra have become more difficult to obtain and the price of rostral teeth has increased significantly. However, some cock-fighting associations are now working to ban the use of spurs made from rostral material and to encourage the use of artificial spurs. In Peru, Planeta Océano is conducting interviews with members of these associations, in order to assess the frequency with which sawfish teeth are still used as spurs and to better understand how cock-fighting associations can encourage their members to use alternative materials. There may be the potential to develop outreach materials that can be used throughout the Americas in countries where cock-fighting is popular, in order to minimise any further threat to sawfishes via the demand for rostral teeth. 

Cock-fighting spurs made from plastic composites.

The collaborative nature of sawfish research in this region is a wonderful example of how, through communication and sharing of resources, numerous small research projects can result in effective data collection and better geographic cover. This collaborative approach is also creating links between NGOs, researchers and government organisations which will enable a smoother transition to the next, equally important phase of this work: developing a regional conservation strategy for sawfishes, in line with the IUCN’s Global Sawfish Conservation Strategy (Harrison & Dulvy 2014). Exciting times for sawfish research and conservation in the Americas!

Many thanks to all the researchers who provided details of their projects for this article, and to the many funders supporting this much-needed work. 
This article first appeared in the IUCN SSG's newsletter, 10th November 2015. 

Become a sawfish researcher for a day!

The Sawfish Conservation Society (SCS) is partnering with researchers from around the world to launch the See A Saw Citizen Science Sawfish Project in order to better understand the highly threatened sawfishes, and you can help!

The See a Saw program and its instructional video can be found at www.sawfishconservationsociety.org

Sawfish numbers have greatly declined in the last 100 years due to fishing and habitat modification and now these fishes are close to becoming extinct. Sawfishes are often caught accidentally, but sometimes fishers kill these animals or cut off their saws to detangle them from nets/fishing lines or to collect a souvenir of their catch. If a sawfish is released alive after its saw has been removed it is unlikely to survive, as it is depends on its saw for hunting and for protecting itself from predators.

Saws from sawfish can be easily entangled in fishing lines and nets. 

Today, sawfish are protected in a large and increasing number of countries, and it is now illegal to harm sawfish, which includes removing their saw, in these countries. In addition, international trading, and in some countries, domestic trading of removed saws is also illegal.

Although the removal of sawfish saws has negatively impacted sawfish, researchers have discovered how to turn this negative into a positive and can use previously collected saws to gain important information on sawfish, which can then be used to conserve the remaining populations of sawfish. This can be very useful as old sawfish saws are easier to find and work with then live sawfish.

A pile of saws collected from fishers, which are being used to better understand the rare and threatened sawfishes.

Recent research has shown that it is possible to identify the species, size and occasionally the sex of a sawfish from its saw. In addition, researchers are now able to extract  DNA from old sawfish saws, which can be used to gather important information about the genetic health and other aspects of the different sawfish populations.  

Scientists are now taking their research one step further and are looking at regional differences between these saws to see if the measurements and tissue samples from these saws can be used to determine where saws come from and how populations have changed through time.

Please measure, take a photograph (as shown above) and report your old sawfish saw to the SCS.

To do this, researchers need a large number of saws from throughout the world and they have asked us at the SCS to reach out to you to help them with this important and large task. Specifically, researchers are asking for you to measure, photograph and report any sawfish saws that you may have. However, it is important to note that you should not hurt a sawfish to obtain this information, nor should you try to obtain this information from a live sawfish. Data collected from this project will not only benefit the current studies, but will also be made available to future research as well.

The Sea a Saw program webpage

If you are interested in becoming a sawfish scientist for a day, please visit our website (www.sawfishconservationsociety.org) and follow the links for the “See a Saw” program. On the webpage you will find multiple links that will take you to the instructions on how to take part in this program, the necessary data sheets and other important information. Please make sure to read all instructions and the disclaimer before you measure and/or photograph your saw.

Updates will be posted on the SCS website as this program progresses, so make sure to check back to look for these updates.

We are looking forward to working with you all and appreciate any information you can provide. Thank you for your help in better understanding these incredible and endangered fishes.

An Inordinate Fondness for Fish Snouts. Part 1: Nature’s Obsession with Sawfish Schnozzles & Other Beastly Beaks

By Jason Seitz. 

What is all the fuss about the sawfish’s toothy muzzle? After all, we know the sawfish is not the only fish to have a tooth-studded nose. And we know it’s not a nose after all. It’s an extension of the skull that we are referring to here. A snout or rostrum, if you will. All those laterally placed spines meet a broad definition of teeth because they are tooth-shaped, are set into sockets (alveoli) within the cartilage of the rostrum, and are used to secure food. The sawfish swings its tooth-studded rostrum from side to side to stun fishes or invertebrates which it then swallows whole.

Fig. 1 (left): Laterally-placed rostral teeth of a juvenile green sawfish (Pristis zijsron). Fig. 2 (right): Fossil rostral teeth and a portion of fossilized rostrum from the extinct sawfish genus Propristis, late Eocene.

The lateral spines along the snout of modern sawfishes (Pristidae) are called ‘rostral teeth’ by scientists (Fig. 1). Indeed, it could be argued that these rostral teeth are more tooth-like than are the oral teeth in sharks and rays, as the oral teeth in these animals are not set into sockets but rather are anchored in soft tissue. The rostrum, like the rest of the skeleton of the sawfish, is composed of cartilage, albeit reinforced with extra calcium. Unlike their oral teeth, the rostral teeth are not replaced if the root becomes damaged. But as long as the roots stay healthy, rostral teeth continue to grow and are sharpened and kept healthy by regular abrasion with the seafloor. Sawfish that are kept in aquaria devoid of soft sandy substrate, such as bare concrete-bottomed tanks, often suffer from dental disease. They develop unattractive irregular pyorrhetic lesions similar to periodontal (gum) disease in people. Captive sawfish kept in this manner over a long period of time develop eroded portions of the rostrum adjacent to the deposits, and some rostral teeth may even fall out or become eroded. Degenerative invasions of the socket can develop where the teeth were lost. Thankfully, many public aquaria keeping sawfish include a layer of sand or similar material to allow the sawfish to maintain healthy, attractive rostral teeth.

The modern sawfish group first showed up in the fossil record between the beginning of the Cenozoic (about 66 million years ago) and the beginning of the Eocene (about 56 million years ago). The only extinct genus (Propristis) had interesting broad flat teeth that were closely spaced along the rostrum (Fig. 2). 

Fig. 3: The anterior portion of a fossil rostrum and associated spines of the Cretaceous sawfish, Onchopristis numidus, Cenomanian.

An extinct group of sawfishes occurred during the Cretaceous period, which lasted from about 145 million to 66 million years ago. Members of the Cretaceous  sawfish group (order Sclerorhynchiformes), which are not related to modern sawfishes, had a wide variety of shapes and sizes of rostral spines (Fig. 3). Why are we calling these rostral spines after we determined that those of modern sawfish are called rostral teeth? The difference is that rostral spines of Cretaceous sawfishes were not set in sockets.  Their spines rested on the surface of the cartilage of the rostrum via connective tissue and probably were regularly replaced in the same conveyer-belt fashion as the oral teeth. Their spines ranged from closely-spaced thin spines to widely-spaced massive barbed spines on sturdy, widened bases.

Fig. 4 (left): Close-up of a rostrum of a saw shark (Pristiophorus sp.) showing the ventrally-placed spines. Fig 5 (right): Close-up of a rostrum of a saw shark (Pristiophorus sp.) showing the laterally-placed spines.

Saw sharks (Pristiophoridae) are true sharks with spines along the rostrum similar to those of Cretaceous sawfishes (which are rays, not sharks). The rostrum is probably used to stun fish and invertebrate prey. Saw sharks differ from modern sawfishes in many ways, including the fact that they possess ventrally placed rostral spines (Fig. 4) in addition to their laterally placed spines (Fig. 5). The rostral spines are not set into sockets. Instead, the spines of saw sharks are set within the skin and are continually replaced (rather than continually growing but never replaced as in the modern sawfishes). There are eight species of living saw sharks, with one (Pliotrema warreni) having serrations on its lateral rostral spines. Saw sharks in the fossil record date back to the Cretaceous (Santonian).

The long, tooth-studded snouts of Cretaceous sawfishes, modern sawfishes, and saw sharks evolved separately and independently. Cretaceous sawfishes and modern sawfishes evolved independently from either the guitarfishes (Rhinobatidae; as suggested by some authors) or the wedgefishes (Rhynchobatidae; Fig. 6). Members of both groups have characteristics that they share with the modern sawfishes.

Fig. 6: The dried head and rostrum of the whitespotted guitarfish (Rhynchobatus australiae). Note the superficial resemblance to that of modern sawfishes.

Scientists have a name for evolutionary adaptation in similar directions, but between different organisms, leading to functionally similar but not identical anatomical features. They call this ‘convergent evolution’. This explains the similar snouts of modern sawfishes, Cretaceous sawfishes, and saw sharks as these unrelated groups each evolved their functionally and physically similar snouts separately.

In Part 2 of this series we’ll discuss paddlefish paddles, billfish bills, and swordfish….. Well, you get the idea!  More anatomical oddities discussed and explained ahead so stay tuned! 

Wueringer BE, Squire Jr L, Collin SP. 2009. The biology of extinct and extant sawfish (Batoidea: Sclerorhychidae and Pristidae). Reviews in Fish Biology and Fisheries 19: 445-464.  

All photographs copyright of Jason Seitz.