Searching for sawfish in Guinea-Bissau
Critically Endangered largetooth and smalltooth sawfishes have likely to have vanished from most of West Africa, but the protected mangroves of Guinea-Bissau may harbour remnant populations. Traditional survey methods, such as netting or fisheries monitoring, are not well suited for species at extremely low densities. So Kayla is searching for sawfish in the Bijagós Archipelago using a cost-effective duplex eDNA assay. eDNA is a non-invasive alternative and pairing it with droplet digital PCR, which can detect a single DNA copy, offers greater sensitivity. She hopes this approach will determine whether remnant populations persist and identify critical habitats to guide targeted conservation and lay the foundation for coordinated monitoring across West Africa.
Kayla McCulloch
I grew up in Punta Gorda, Florida, where learning to sail on the coastal waters introduced me to marine life such as dolphins and schools of rays, sparking a lifelong fascination with the ocean. This curiosity eventually led me to pursue a Bachelor’s degree in marine biology and ecology at the University of Miami. As an undergraduate, I had the chance to participate in field surveys for juvenile Critically Endangered smalltooth sawfish in the same waters where I learned to sail. This experience left a lasting impression and inspired my passion for elasmobranch conservation. I later completed an...
Searching for sawfish in Guinea-Bissau
The overall objective of this project is to determine whether largetooth sawfish and smalltooth sawfish persist in Guinea-Bissau’s Bijagós Archipelago by developing a duplex environmental DNA (eDNA) assay and screening eDNA field samples for evidence of the species’ presence.
The Critically Endangered largetooth sawfish and smalltooth sawfish have probably vanished from most of West Africa, yet Guinea-Bissau’s protected mangroves may harbour remnant populations. This project will assess whether sawfish occur in the Bijagós Archipelago using a cost-effective duplex eDNA assay. eDNA surveys increase the likelihood of detection for rare species and can generate ‘informative zeros’, providing evidence of persistence or extinction. Results will guide conservation priorities, inform management and support recovery efforts for sawfish in West Africa.
The loss of marine biodiversity is an escalating crisis, and sawfish rank among the most imperilled vertebrates, now presumed extinct from more than half of their historical range. This highlights the urgent need to identify remaining populations for targeted conservation action. West Africa is a region of particular concern, where the largetooth sawfish Pristis pristis and smalltooth sawfish P. pectinata were historically found from Mauritania to Angola.
Coastal estuaries in West Africa once provided ideal habitats for sawfish, but populations have suffered alarming declines in recent decades. Their toothed rostra make them especially vulnerable to entanglement in fishing gear, while slow growth and low reproductive rates hinder recovery. These traits, intensified by gill-net use, extensive loss of mangroves and global demand for shark fins have driven severe regional declines.
The status and distribution of sawfish in the Eastern Atlantic is poorly understood. Most information comes from fisher interviews or relic rostra, pointing to times when sawfish were more common. Reports suggest they may persist in several countries and identifying ‘lifeboat’ habitats is critical. In Guinea-Bissau the last confirmed records date to 2012, and the country’s Bijagós Archipelago could harbour one of the region’s final populations due to its extensive protected mangroves.
The lack of consistent monitoring efforts poses a major challenge to sawfish conservation. Traditional survey methods, such as netting or fisheries monitoring, are not well suited for species at extremely low densities. Environmental DNA (eDNA) offers a powerful, non-invasive alternative that is effective for detecting exceptionally rare species such as sawfish. When paired with droplet digital PCR, eDNA can detect a single DNA copy, offering much greater sensitivity. In Guinea-Bissau, this approach can help to determine whether remnant populations persist and identify critical habitats. As well as revealing persistence or local extinction, these insights can guide targeted conservation and lay the foundation for coordinated monitoring across West Africa.
- To develop a duplex eDNA assay to simultaneously detect and distinguish largetooth sawfish and smalltooth sawfish from environmental samples in a single reaction.
- To screen eDNA field samples to determine whether sawfish persist in Guinea-Bissau.
- To support sawfish conservation awareness in Guinea-Bissau by sharing eDNA results and leveraging existing educational resources.