Madelyn Roycroft

Biological Science Master’s Candidate-Cal Poly, San Luis Obispo

 Master's Scholarship Recipient, 2016

“Crunch... crunch... crunch.” I will never forget the first time I heard the unforgettable sound of a parrotfish grazing on coral reefs. Nearly two years after hearing that sound for the first time, I, along with my research team and hundreds of pounds of scientific dive equipment, headed from California to the Caribbean. The island of St. Croix, part of the U.S. Virgin Islands, was our destination; our mission: to get to know these charismatic parrotfishes on a more personal level. Our focus was to study the feeding behavior of the resident parrotfish species, who are important herbivores in coral reef systems.

Herbivory on coral reefs is a recent focus of research, as herbivores often consume algae in a way that is beneficial to the growth and recovery of live coral. Parrotfishes are an abundant herbivore on coral reefs and provide a plethora of positive impacts, particularly by consuming a significant amount of algae on the reefs. Interestingly, each parrotfish species, which come in an assortment of colors from stunning greens and blues (Image 1)  to rainbow sherbet (Image 2), plays a unique role in their community. For example, the Queen parrotfish, Scarus vetula eats mostly small turf algae on complex reef structure, while the Yellowtail parrotfish, Sparisoma rubripinne prefers a bushy, brown macroalgae on a range of substrate types. Our current knowledge of parrotfish behavior comes from studies conducted in locations that have an abundance of each key parrotfish species. However, in some locations such as St. Croix, these fishes are an important source of nutrition, income and cultural value to the local fishing community and are thus subject to high fishing pressure and species loss.
My project as a California Polytechnic State University Master’s student in the Ruttenberg lab, supported by the Kevin Gurr Scholarship, was to determine whether fishing pressure and subsequent species loss has had an effect on parrotfish feeding behavior, and ultimately their positive impact on the coral reefs. We gathered feeding behavior data by using SCUBA and followed individual parrotfishes of each species for 20 minutes at three sites around the island (Image 3). During this time we recorded data such as what food each fish ate and how many bites it took, all while towing a surface float with a GPS unit to track how far the fish traveled (Image 4). A highlight of this study was to be able to dive the beautiful Buck Island Reef National Monument (Image 5).  I was prepared for this challenging data collection technique thanks to my rigorous AAUS scientific diving training through the University of North Carolina Chapel Hill and experience as a dive technician prior to my graduate studies.

Although research is still ongoing, my data so far has shown that, broadly, parrotfish species in St. Croix play similar roles to the same species in other Caribbean locations. At a higher-resolution, we do see fine-scale differences in feeding behavior, but we are still working to determine if fishing pressure, species loss, or other environmental variables caused such differences. We also found that three key parrotfish species typically found throughout the Caribbean were absent from the reefs on St. Croix. Similar to the dysfunction and loss of productivity if a restaurant were to lose entire positions such as cooks, servers, and receptionists, this absence indicates the loss of important roles from these St. Croix reefs and potential decline in reef condition if these roles remain unfilled

The Kevin Gurr scholarship not only provided me the means to conduct a dive-intensive field season in the Caribbean to answer important ecological questions, but also gave me the opportunity to develop important relationships with members of the St. Croix fishing community, National Park Service and the University of the Virgin Islands. Over the course of three seasons in St. Croix, I developed relationships of trust and respect with local fishermen who granted me rare access in personal interviews to the family traditions and food-dependence associated with parrotfish and other species. Through conversations with these individuals, I learned the importance of incorporating both cultural and ecological value into metrics for fisheries management in collaboration with local residents. I hope to maintain the relationships that I made through this project and continue to promote discussions between the fishing community, scientists, and policymakers on how to manage the parrotfish fishery in St. Croix in a way that will result in measurable success for all stakeholders.

So, the next time you have the opportunity to snorkel or dive on a coral reef, take the time to listen for that unmistakable “crunch,” and observe the parrotfishes that are crucial to maintain the health of our beautiful coral reefs. You never know what interesting behavior you might witness!
Thank you AAUS for awarding me the Kevin Gurr scholarship and the opportunities that came from it.