Damselfishes are considered the “poodles of the sea” for their active defense of food resources within their territories against predators up to 50 times their own body size. During this summer’s Field Study in Belize course, current students, guided by a recent alumna, were able to investigate damselfish territoriality on coral reefs.
Among the damselfishes, territorial grazers are numerically dominant to other herbivorous fishes and have a large ecological role in shaping the community of coral reefs. Due to their territoriality, they are ideal study species on the two largest coral reef systems in the world: the Great Barrier Reef (Australia) and the Belizean Barrier Reef.
Field Study in Belize is a 10-day intensive immersion course in which Sewanee students study rainforest and coral reef ecosystems in Belize. The course is led by Professor Jon Evans of the Biology Department and assisted by Jordan Casey (C’09 and current Ph.D. candidate in marine biology at James Cook University). On the Great Barrier Reef, Casey studies territorial grazer behavior and community structure. To expand upon Casey’s research on the Great Barrier Reef, several Sewanee students conducted damselfish projects at South Water Caye on the Belizean Barrier Reef.
One component of Casey’s research shows that territorial grazers exhibit strong diurnality. Early in the day, they “farm” their territories by weeding unwanted algal species and pecking at coral to perpetuate preferred algal species. Later in the day, they feed on their algal farms. Her research further distinguishes territorial grazers into two categories: intensive and extensive grazers. Intensive grazers cultivate small monocultures and are extremely aggressive. Extensive grazers have large territories that include several species of algae and are notably less aggressive.
Students Meg Armistead and David Evans (left) found that territorial grazers in Belize demonstrate diurnality similar to the patterns shown by damsels in Australia. Further, they identified the Threespot Damselfish as an intensive grazer and the Yellowtail Damselfish as an extensive grazer. Students Ashley Block, Joanna Parkman and Carolyn Ramseur investigated parrotfish herbivory in the presence and absence of territorial grazers. Due to the aggression of the Threespot Damselfish, parrotfish herbivory was significantly deterred in damselfish territories.
Despite profound differences in coral cover and predator abundance on the Great Barrier Reef and the Belizean Barrier Reef, Casey and the students found that territorial grazers seem to exhibit characteristic diurnal and aggressive behaviors in both systems.
More about Jordan Casey, C’09:
Jordan Casey (right) was Sewanee's 27th NCAA Postgraduate Scholar. A double major in Spanish and biology and a member of the tennis team, Casey was a 2009 Academic All-American and a member of Phi Beta Kappa, and won the Robert Woodham Daniel Prize in Expository Writing. In 2010 she was selected to receive an Omicron Delta Kappa Foundation Scholarship. On Sewanee’s tennis court, Casey was a member of the 2007 SCAC All-Tournament team and played on NCAA Tournament teams in 2006, 2007, and 2008.