Sawfishes are rapidly disappearing from our seas, so when a healthy population was discovered off Andros Island in The Bahamas, the area became a very important place. Dean aims to understand this rare community of sawfishes in order to protect them.
I am a fish ecologist and much of my research is geared towards providing answers needed for the sustainable management and conservation of coastal and deep-water sharks and rays. A Florida native, I grew up fishing and exploring the waters of the north-eastern Gulf of Mexico, which led to an early interest in marine biology in general, and a fascination for sharks and rays in particular. Studies at the University of Miami, a PhD through the College of William & Mary’s Virginia Institute of Marine Science, and a post-doctoral stint at the University of Hawaii gave me the opportunity, and...
A key challenge to sawfish conservation and recovery is identification of existing critical habitats. Using genetic analysis in concert with satellite telemetry and acoustic monitoring, we will determine whether smalltooth sawfish in The Bahamas constitute a genetically and demographically distinct breeding population that could contribute to species recovery.
Sawfishes typify the challenge of assessing and conserving widely distributed marine fishes. Smalltooth sawfish have been extirpated from large parts of their range, suggesting that unless effective conservation measures are in place, there is a significant risk of extinction in the wild. The west side of Andros Island in The Bahamas is one of the most remote and unaltered tropical systems in the Atlantic Ocean and has recently been designated a national park, potentially protecting these pristine habitats in a country where a tourism-based economy has traditionally led to gross over-development and habitat degradation. Thus, the Andros West Side National Park could represent a 1.3 million-acre ‘lifeboat’ for smalltooth sawfish in the western Atlantic, but data are lacking on how sawfish use the park and their movements within the larger Caribbean basin. Such remote areas are exceedingly difficult to effectively monitor, however, and regulations are difficult to enforce. Data concerning movement patterns, habitat use and population genetics collected as part of this study will elucidate the ecological importance of Andros Island to the recovery of smalltooth sawfish. Following the successful designation of The Bahamas as a shark sanctuary, our work may stimulate legislation to protect sawfishes in The Bahamas.
Sawfishes are a small group of batoids possessing a long, toothed rostrum used for defence and feeding. Worldwide, there are five living species of sawfishes and together they represent the most imperilled family of elasmobranchs. Sawfishes occur in coastal tropical waters where they are captured by fisheries as their rostra are highly susceptible to entanglement in fishing gear. Sawfishes also require habitats, such as mangroves, that are highly sensitive to degradation from pollution and development.
The smalltooth sawfish Pristis pectinata is found in the Atlantic Ocean and is the only sawfish species native to the United States and the islands of the Caribbean basin. The US population of smalltooth sawfish has declined considerably and its range, which has contracted primarily as result of overfishing, is principally restricted to south-west Florida. This is likely to be the only remaining region with a reproductive population. A critical factor determining the likelihood of smalltooth sawfish recovery is the amount of genetic exchange between population segments. For example, if south-west Florida is the only remaining nursery in the US and this population is closed, then genetic bottlenecks may limit recovery. However, if there is mixing with adult sawfish from other regions, the likelihood of recovery increases.
Records of smalltooth sawfish exist throughout The Bahamas, although it is not known if the population in The Bahamas is distinct or part of the US population.
In 2010, we began a pilot study using satellite telemetry to track sawfishes in The Bahamas. We successfully tagged three large juvenile sawfish in Andros, none of which emigrated out of the area over the 60-180 days the tags were deployed. Local fishing guides continue to provide us with information about the sawfishes they see in the area, including photographic evidence of a young-of-year sawfish. The entire region where sawfishes are known to occur in Andros has recently been designated as the Andros West Side National Park, which could prove critical to the recovery of the species.
The aims and objectives of this project are to:
Gregg will use environmental DNA (eDNA), a scientific method that marine biologists have only recently begun to employ, to track sawfishes in Florida. He will determine whether they still use the same nursery areas that they used in the past and learn about their range and whether that range is expanding.
Sawfishes have vanished from much of their historical range, but reports from Papua New Guinea suggest that it might be one of the few remaining sawfish strongholds. With help from local students, Will hopes to identify where the animals can still be found and how they fit into the local culture and economy.