Kelton McMahon is a post-doctoral fellow with joint appointments at Woods Hole Oceanographic Institution in the US and KAUST in Saudi Arabia. Kelton received his B.S. in Biology from Bates College in Maine, USA and recently completed his Ph.D. in Biological Oceanography from the MIT-WHOI Joint Program in Oceanography under Simon Thorrold. He was a National Science Foundation Graduate Research Fellow and an International Society for Reef Studies/Ocean Conservancy Coral Reef Research Fellow. He is currently developing compound-specific stable isotope techniques to address questions of diet and movement patterns in marine fish, focusing primarily on tropical seascapes.
Many coral reef fish species use mangroves and seagrass beds as juvenile nurseries before migrating to coral reefs as adults. Identifying essential habitats and preserving functional linkages among these habitats is likely necessary to promote ecosystem health and sustainable fisheries on coral reefs. This necessitates quantitative assessments of functional connectivity among essential habitats at the seascape level. This study presents the development and first application of a method for tracking fish migration using amino acid (AA) d13C analysis in otoliths. Using our otolith AA stable isotope analysis approach, we quantified the relative contribution of coastal wetlands and reef habitats to Ehrenberg’s snapper, Lutjanus ehrenbergii, populations on coastal, shelf and oceanic coral reefs in the Red Sea. Otolith essential AA d13C values were better able to identify residence in juvenile nursery habitats than conventional bulk stable isotope analyses. Lutjanus ehrenbergii made significant ontogenetic migrations, traveling more than 30 km from juvenile nurseries to coral reefs and across deep open water. We showed that coral reef habitats could contribute significant numbers of individuals to the adult population, even when juveniles were not visually abundant in those habitats. Coastal wetlands were important nurseries for L. ehrenbergii; however, there was significant plasticity in L. ehrenbergii juvenile habitat requirements. Seascape configuration played an important role in determining the functional connectivity of L. ehrenbergii populations in the Red Sea. This study illustrates a valuable new compound-specific geochemistry approach to reconstructing diet and movement patterns of fishes. This information is key to determining the importance of nursery habitats to coral reef fish populations and can provide valuable scientific support for the design of networked marine protected areas.