On International Sawfish Day and every day, we stand in celebration of the sawfish and remember a beloved colleague who dedicated his career to these critically endangered elasmobranchs.
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We admit, they don't look particularly approachable, but the largetooth sawfish you can spot in our Shark Alley habitat are some seriously extraordinary elasmobranchs. Sawfish are more closely related to rays than sharks or fish, but like all rays, sharks and skates—collectively known as elasmobranchs—their skeletons are made of cartilage. Just one look reveals their namesake characteristic: A long, tooth-lined rostrum or snout that might remind you of a saw. Largetooth sawfish like the two males on exhibit here typically have about 14 to 23 large teeth protruding from their rostra. While these teeth aren't used for chewing, they do use their "saws" as a weapon or digging tool when seeking out the fish and crustaceans they prey upon. Their saws also have small pores that can detect electric signals emitted by their prey even in the dark, an ability shared by sharks and other rays.
Like the largetooth sawfish at the National Aquarium, all five species of sawfish (largetooth, smalltooth, green, dwarf and narrow) are critically endangered according to the International Union for Conservation of Nature, and their populations are decreasing in their natural range. Sawfish are circumtropical, which implies that they could or once did appear in tropical or subtropical waters around the globe, but there are so few sawfish left in their natural habitats that sightings anywhere are rare. They are even rare in zoos and aquariums, with fewer than 15 members of the Association of Zoos and Aquariums (AZA) featuring sawfish of any species in the U.S.
Sawfish have been swimming in the world's oceans for 60 million years and are remarkable in their ability to tolerate a large range of water salinity, sometimes leaving the ocean and moving well into fresh waterways. And, considering their unique anatomy and the fact that they are not marine mammals, you might be surprised to learn that sawfish give birth to live pups. Scientists have also been able to determine that, in isolation, sawfish are capable of parthenogenesis, which is the ability to reproduce asexually. There's no denying, sawfish are fascinating.
Perhaps these unique characteristics and adaptations are why the humble sawfish has such a devoted following within the scientific community. International Sawfish Day is celebrated every year on October 17 and was established as a collaboration between the AZA Sawfish Species Survival Plan (SSP) and the European Association of Zoos and Aquaria (EAZA) studbook program, as well as research and conservation organizations around the world, to highlight endangered sawfish and the challenges they face in our oceans. Sawfish are largely endangered due to human impacts, including habitat loss from modifications to nearshore habitats that young sawfish need to survive; unintentional entanglement in commercial fishing nets, known as bycatch; and international trade of sawfish or their rostra, which—while illegal—is not always well enforced.
Scientists and aquarists understand that the role sawfish play as top predators is crucial to maintaining balanced coastal ecosystems. By controlling the populations of the smaller fish, crustaceans and ocean scavengers they eat, sawfish help to keep their habitats in check. Without these top predators, delicate tropical habitats including coral reefs are further at risk. The goal of International Sawfish Day is to prevent species extinction by alerting the public to the plight of the sawfish, encouraging recreational and commercial fishing communities to release sawfish threatened by bycatch, and to record and report sawfish sightings in the ocean to allow researchers to zero in on existing populations of these elusive species.
This year on International Sawfish Day, the sawfish research and conservation community is honoring the loss of a legend, National Aquarium Fishes Research Specialist and Senior Aquarist Alan D. Henningsen. Alan passed away in 2021 after 32 years as our resident elasmobranch expert, sawfish advocate, and a notable figure in the larger elasmobranch research community outside of our walls. A sawfish research grant named for Alan will be granted this month by the AZA Sawfish SSP. The funding attached to this grant will be awarded to research pursuing a better understanding of sawfish and the advancement of sawfish conservation efforts. Our aquarists, many of whom worked with and were mentored by Alan, can think of no better way to perpetuate the legacy of this dedicated and respected scientist.
Born in Indiana, Alan's love for the ocean and its inhabitants led him to a master's degree in marine biology from the University of Miami. After years of traveling the world, from the Florida Keys and the Bahamas to Egypt and Israel exploring sharks in the Red Sea under renowned shark researcher Dr. Samuel H. Gruber, Alan's heart led him to the National Aquarium when he met and married his wife of 31 years, Nanci, a native Baltimorean.
Stepping into the role of full-time aquarist and researcher, Alan's expertise was critical to the evolution of our Shark Alley habitat and other spaces within Blue Wonders and, eventually, to the acquisition of two sawfish in 2004. Bolstered by his experience handling large animals, our staff looked to Alan for his guidance and leadership. Aquarist Lindsay Fitzpatrick cites Alan as the foundation of her interest in and affection for the two sawfish that arrived here as juveniles.
"Alan's enthusiasm for and knowledge of elasmobranchs were an inspiration to all of us," she says. "I'll always think of him as we continue his work."
Among those projects is the ongoing process of training our sawfish to cooperatively participate in their own routine medical care, a skill that builds upon their training to respond to a specific station within their exhibit for feedings.
Assistant Curator Jennie Janssen agrees that Alan was an inspiration to our team, and other professionals well beyond our building.
"Alan managed to keep one hand in elasmobranch research in the ocean while keeping the other in the husbandry of these animals in zoos and aquariums," Jennie explains. "His ability to bring those two sometimes separate worlds together is a testament to how loved and respected he was within both."
To those closest to him, Alan is remembered as a man of profound faith and kindness who relished his dual role as researcher and hands-on aquarist. Here at the National Aquarium, he embraced the opportunity to share his immense knowledge with guests—especially curious children who were quick to respond to his soft-spoken expertise—and his work shone a light on the little-known sawfish and their vulnerable conservation status. It is a comfort to all of us at the National Aquarium that the grant bearing his name will assure that dedicated scientists can continue in this pursuit.