The largetooth sawfish, an enigmatic species on the brink of extinction

Today, October 17th, we celebrate International Sawfish Day. This group of five species closely related to sharks is still relatively unknown to many, yet they are fascinating and unique creatures deserving our full attention. This is why today we want to highlight the ongoing research and conservation efforts to protect one of these species, the largetooth sawfish (Pristis pristis), one of the most widely distributed sawfish species but currently listed as critically endangered. Mario Espinoza, a researcher at the University of Costa Rica and a member of MigraMar, has dedicated years to studying this species in Costa Rica. 

Habitat and Characteristics

The largetooth sawfish inhabits rivers, estuaries, and coastal marine areas. It can grow over six meters long, and its distinctive rostrum is also functional, as it contains sensory organs that allow it to detect prey such as invertebrates and fish. Although more research is needed, we know that the largetooth sawfish is a migratory species capable of moving hundreds of kilometers between freshwater and marine areas. Juveniles usually inhabit riverine and estuarine zones, while adults are more commonly found in coastal marine zones. 

Unfortunately, the largetooth sawfish is critically endangered. Bycatch is one of its main threats, as its rostrum becomes easily entangled in fishing nets. Historically, sawfish have also been captured as trophy species. Along with the degradation of coastal and estuarine habitats, these threats have pushed this species to the brink of extinction. 

An inspiring encounter

Surprisingly, Mario’s first encounter with a sawfish was not in Costa Rica, but in the United States. While still a biology student in Costa Rica, Mario participated in fishing expeditions in search of sawfish in the Everglades, the iconic wetlands of Florida. After months of searching, the team captured a juvenile individual to which they attached an acoustic transmitter to track its movements through the dense mangroves. This unforgettable experience sparked Mario’s interest and motivation to study the species in Costa Rica. 

In Search of the Sawfish

In 2016 Mario launched the Project “Buscando al Pez Sierra” or In Search of the Sawfish. As a first step, Mario and his team interviewed coastal and riverine communities in Costa Rica to gather information on the historical and current distribution of sawfish. This traditional ecological knowledge was crucial in gaining insight into where the species was found decades ago and more recently. From these interviews, two key areas were identified: the San Juan River at the northern border with Nicaragua and the Térraba Sierpe National Wetland in the southern Pacific region. 

In the second phase of the project, Mario and his team used environmental DNA (eDNA), an innovative technique consisting of analyzing water samples to identify traces of the genetic material of species that inhabit the area. The results confirmed the presence of the largetooth sawfish in the San Juan River and Barra del Colorado (Northern Caribbean Coast). 

In the third phase, the team conducted fishing expeditions. After several trips with no luck finding any specimen, in 2022, they captured a sawfish over 3.5 meters long in Boca San Carlos, located along the San Juan River. This capture not only highlighted the importance of this region for sawfish but also revealed that adults inhabit freshwater areas in Costa Rica. This encounter emphasized the importance of continuing to study this species. 

Hope for the Sawfish

The search and research on sawfish is not an easy task. It requires a lot of dedication and perseverance. Despite its critical conservation status, Mario is convinced that there is still hope for this species in Costa Rica and the Eastern Tropical Pacific. He believes that it is crucial to identify and protect the habitats of sawfish and coordinate conservation efforts across countries to ensure their survival. Additionally, holding educational workshops is essential to raising awareness about this species and its threats. There is still time to contribute to sawfish conservation!

For more information about this project, visit: 

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