Project

All about sawfish in the Bahamas: tracking movement, breeding and nurseries

Species
  • Rays & Skates
Years funded
  • 2021
Status
  • Active
Project types
  • Conservation
  • Research
Description

Dean’s research is focused on the biology and ecology of the smalltooth sawfish, and he concentrates his efforts around the island of Andros in the Bahamas. As the largest island in the Bahamas, Andros is the least densely populated and its remote west side is nearly pristine. Dean collects blood from smalltooth sawfish to assess reproductive status, muscle samples for food web analyses and fin clips for genetic studies. He tags each sawfish, which is then tracked by satellites and acoustic receivers, to know more about where these animals move, what they do and how best they can be conserved.

All about sawfish in the Bahamas: tracking movement, breeding and nurseries

Dean Grubbs

Project leader
About the project leader

I am a fish ecologist with interests in the biology of exploited and poorly studied estuarine and marine taxa. Much of my research addresses specific biological gaps necessary for the management and conservation of coastal and deep-water sharks and rays, including research on endangered smalltooth sawfish. My interest in sharks stems from being raised fishing and exploring Florida’s Gulf coast. I received Bachelor’s degrees in marine science and biology from the University of Miami and a PhD in fisheries science from the College of William & Mary’s Virginia Institute of Marine Science. I was a post-doctoral researcher and faculty member...

PROJECT LOCATION : The Bahamas
Project details

All about sawfish in the Bahamas: tracking movement, breeding and nurseries

Key objective

Our primary goal is to conduct research that supports and promotes recovery of critically endangered smalltooth sawfish in the Bahamas. Our objectives are to determine the population size and viability of sawfish population, to assess the probability of recovery and to determine what habitats are critical to their continued survival.

Why is this important

The sawfishes are among the most imperiled of all families of sharks and rays. All five species in the group are currently listed as Endangered or Critically Endangered. The Critically Endangered smalltooth sawfish is endemic to the Atlantic basin and their only known viable populations are in the United State and the Bahamas. Our research seeks to address questions and provide data that assist efforts to promote recovery of this iconic species.

Background

The sawfishes include five living species of very large rays and all listed as Endangered or Critically Endangered according to the IUCN Red List of Threatened species. Sawfishes have a large toothed rostrum that used for defense and immobilizing prey, but also makes them vulnerable to fishing nets. The smalltooth sawfish is the only found in the Atlantic and the U.S. supports the most robust population of smalltooth sawfish though it declined severely due to overfishing, including harvest for the rostra (highly sought as curios), and habitat loss. In 2003, the smalltooth sawfish became the first marine fish listed as Endangered under the United States’ Endangered Species Act.    Our research suggests reproducing population of smalltooth sawfish exists also in the Bahamas, primarily on the west side of the island of Andros. With SOSF support, in 2016 we were the first to ever witness the birth of baby sawfish, thus confirming sawfish give birth in Andros. Our tracking data from U.S. and Bahamas tagged sawfish suggest the populations are isolated and recovery of these two smalltooth sawfish populations may be critical to species recovery, hence the IUCN Shark Specialist Group designated the U.S. a ‘Lifeboat’ population and the Bahamas a ‘Beacon of Hope’ in their 2018 SAVING SAWFISH: Progress and Priorities update.   The west side of Andros is very remote and pristine and much of the sawfish habitat is within Andros West Side National Park. Our data suggest the sawfish population in Andros is much smaller than that of Florida in spite of comparable habitat. This may be due to differences in protective habitat, available food, the density of sharks that compete for food, or the number of predators that feed on young sawfish. We seek to unravel these mysteries to assess the likelihood of recovery of the Bahamas sawfish population.

Aims & objectives

Key challenges to sawfish conservation are the ability to estimate and monitor changes in population sizes and to identify habitats critical to survival and recovery. We seek to determine the relative size of the Bahamian smalltooth sawfish population compared to the U.S. population, to define habitats that are critical to survival (e.g. nursery habitats), and examine ecological processes the influence changes in the Bahamas smalltooth sawfish population. We will use our baited line surveys and and records of sawfish sightings to estimate relative abundance of smalltooth sawfish and coastal sharks that serve as sawfish competitors or potential sawfish predators. We will examine overlap between sawfish and sharks in the Andros food web, as a proxy for determining shark species that may compete with sawfish for prey as well as those that may prey on juvenile sawfish. Smalltooth sawfish will be implanted with long-term acoustic transmitters that, along with previously tagged sawfish, are detected by existing SOSF sponsored acoustic receiver arrays in Andros and Bimini. These data will be used to monitor sawfish residency and long-term movements and migrations as functions of temporal and spatial fluctuations in variables such as salinity, tidal cycles, and salinity over days, seasons, years. This will also allow us to monitor how often adult females return to know habitats where they give birth. We will use blood samples to determine if females are mature and reproductively active. Genetic material from adult female and young-of-year sawfish will be used to potentially link offspring with their mothers and determine how frequently females return to give birth. In addition, our data will provide baseline information concerning primary sawfish habitat should development take place that affects the habitats negatively.