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Award Winner Q & A - Sarah Hoffman

Q. What award did you receive and when?

American Elasmobranch Society Research Award, in 2017

Q. What degree are you seeking, from what institution, under whose guidance?

Florida Atlantic University, Ph.D., Marianne Porter

Q. What is the most important (actual or potential) finding of your research?  Give us a little background on the subject.

There are conflicting hypotheses about the role of shark pectoral fins, likely confounded by the vast morphological diversity observed in this group. Historically, pectoral fins are most often compared to airplane wings and hypothesized to generate lift to keep the shark aloft in the water column. However, recent studies demonstrate that for a least one species, negligible lift is generated by the pectoral fins during swimming. Additionally, previous studies focus primarily on the depression and elevation of fins that is thought to initiate vertical maneuvering. From this, we know that pectoral fins rotate in at least one plane but the morphology of the joint between the body and fin suggests that fins may be able to rotate in other planes. I have found that Pacific spiny dogfish (Squalus suckleyi) rotate their fins in three planes when turning. The pectoral fin on the inside of the turn is protracted, supinated, and depressed predictably when these sharks maneuver horizontally. This rotation of the fin increases the area of the fin to oncoming flow which we hypothesize creates a moment that converts some of the shark’s forward momentum into torque, facilitating turning behavior.

Q. How is the award going to help you complete the project?

This award will allow me to study the fin movements of another species. Due to the extreme morphological and ecological variance within sharks, we hypothesize that fin movement changes with differing morphology, swimming style, and habitat use. We will be examining pectoral fin rotation in the epaulette shark (Hemiscyllium ocellatum) which is known to ‘walk’ both along coral reef habitats as well as out of the water between tidepools.

Q. What are your other research goals?

The goal of my dissertation is to describe the functional ecomorphology of shark pectoral fins. I am describing the diverse biomechanical and morphological properties of fins from as many species as I am able to sample and compare among species in an ecological and phylogenetic sense. From this, I hope to better understand how sharks from varying environments are adapted for differing habitat use. In a broader sense, understanding how hydrofoils (the pectoral fins) function in different environments, which could inspire the design of autonomous underwater vehicles. For example, it would likely be inefficient to have a drone with large, broad hydrofoils similar to the pectoral fins of pelagic sharks that is meant to navigate and monitor coral reefs.

Q. How did you get started in research/shark bio/science?

I have always been interested in how movement is produced among animals with very different shapes and sizes. I was fortunate to do undergraduate research in Florida Keys and was quickly sold on marine science. Sharks are of particular interest because they inhabit many different environments throughout the ocean and have extremely variable bodies. I hope to better understand how such a diverse group of animals have proliferated in so many different habitats.