by Tonya Wiley, Havenworth Coastal Conservation
Several research partners conduct various research activities on the biology, behavior, and ecology of the endangered smalltooth sawfish population in the United States. These partners include state and federal governments, universities, nonprofits, and international organizations. The results of these research projects are used to inform management decisions and enhance recovery efforts for this endangered species.
Collecting Sawfish Data
Researchers collect sawfish data using a variety of methods: (1) carcasses that are found and collected, (2) sawfish incidentally caught in federal fisheries, and (3) sawfish that are collected during research field surveys for the species. Necropsies of sawfish carcasses provide the opportunity to collect data necessary for understanding age, growth, maturity, and reproduction. Carcass recoveries provide valuable opportunities because these data are especially important and can only be collected through dissection, and researchers are not interested in sacrificing any individuals from the wild of a critically endangered species.
Fisheries observers aboard commercial fishing vessels are trained to sample any sawfish incidentally captured in federal fisheries. These chance opportunities provide valuable insight in to where fisheries overlap with sawfish and the condition of sawfish upon release.
Research field surveys for smalltooth sawfish are the most important method for collecting data. A variety of survey methods are used to capture live sawfish for scientific purposes, including longline, rod-and-reel, and gillnets. Once captured, measurements and samples are taken from each sawfish prior to tagging and release. These surveys are instrumental in monitoring trends in the abundance of the population.
Small tissue samples are collected during field capture of live sawfish and from old rostra for genetic analysis. Genetics are useful in understanding population structure, diversity within the population, and both the size and health of the current population in comparison to the historical one. Scientists are using genetics to determine whether there is significant movement and genetic exchange between the U.S. and Bahamas populations of smalltooth sawfish.
Blood samples are collected from sawfish to measure reproductive status and stress physiology. Hormones within the blood are used to assess reproductive cycling and periodicity. Blood samples for stress physiology can be used to assess post-release mortality risk from a variety of fisheries and gears.
Scientists are using the most recent technology to track the movements of smalltooth sawfish. This tracking involves capturing the animals, equipping them with acoustic transmitters, and releasing them. Depending on the objectives of the project, scientists may track them from a boat using hydrophones to determine short-term microhabitat use or set up a network of in-water receivers (acoustic listening stations) to track longer-term broad-scale movements. Acoustic transmitters can be active for up to 10 years.
Larger juvenile and adult sawfish caught during surveys are also often fitted with GPS satellite tags. Because far less is known about these larger animals, researchers hope that satellite tags can reveal important adult habitats. Satellite tagging studies to date have shown that larger sawfish spent a large portion of their time in shallow coastal waters with periodic excursions to deeper waters off the shelf edge.
Population Monitoring Through Encounter Reports
If you catch or see a sawfish take a quick photograph of the sawfish, estimate its size, note your location, and please share the details with scientists. The details of your sightings or catches of sawfish help to monitor the population and track the recovery progress. You can share your information by calling 1-844-4-SAWFISH (844-472-9347) or emailing email@example.com.
In upcoming “Sawfish News” articles this year I will provide more details about the organizations working on each of these important components of the sawfish research projects.
For more information about endangered sawfish, visit:
or call 1-844-4SAWFISH