Linking habitat mosaics and connectivity in a coral reef seascape

Abstract

Tropical marine ecosystems are under mounting anthropogenic pressure from overfishing and habitat destruction, leading to declines in their structure and function on a global scale. Although maintaining connectivity among habitats within a seascape is necessary for preserving population resistance and resilience, quantifying movements of individuals within seascapes remains challenging. Traditional methods of identifying and valuing potential coral reef fish nursery habitats are indirect, often relying on visual surveys of abundance and correlations of size and biomass among habitats. We used compound-specific stable isotope analyses to determine movement patterns of commercially important fish populations within a coral reef seascape. This approach allowed us to quantify the relative contributions of individuals from inshore nurseries to reef populations and identify migration corridors among important habitats. Our results provided direct measurements of remarkable migrations by juvenile snapper of over 30 km, between nurseries and reefs. We also found significant plasticity in juvenile nursery residency. Although a majority of individuals on coastal reefs had used seagrass nurseries as juveniles, many adults on oceanic reefs had settled directly into reef habitats. Moreover, seascape configuration played a critical but heretofore unrecognized role in determining connectivity among habitats. Finally, our approach provides key quantitative data necessary to estimate the value of distinctive habitats to ecosystem services provided by seascapes.amino acid | Lutjanus ehrenbergii | mangroves and seagrass | otoliths | Red SeaT he ecological integrity of tropical marine habitats, including mangroves, seagrass beds, and coral reefs, is coming under increasing pressure from human activities (1-3). Habitat destruction and unsustainable exploitation, including mangrove deforestation and overfishing, have led to declines in the function and resilience of these ecosystems on a global scale (4). Efforts to promote ecological integrity and sustainable harvest have traditionally focused on protecting coral reefs. More recently, attention has been directed at the issue of preserving critical seascape functions as well as habitat types, with particular emphasis on seascape connectivity (5). For example, many commercially and ecologically important coral reef fishes, including species of Lutjanidae (snappers), Serranidae (grouper), and Scaridae (parrotfish), use mangroves and seagrass beds as juvenile nursery areas before presumably migrating to coral reef habitats as adults (see reviews in refs. 6-8). Preserving seascape connectivity is therefore likely necessary to maintain coral reef ecosystem function and healthy fisheries (9). However, it has proved remarkably difficult to develop quantitative assessments of habitat use and movements among different habitat types for any reef fish species (10). This lack of quantitative data on seascape connectivity represents a major obstacle to marine spatial management (5) and attempts t...

Wild fish aggregations around fish farms in the Gulf of Aqaba, Red Sea: implications for fisheries management and conservation

“…Whereas larval and juvenile fishes often migrate great distances from the reefs they originated in (e.g. Palumbi 2003, McMahon et al 2012, it is believed that the home range of the adults of these species is limited (Zeller et al 2003). Although many reef species generally do not exceed a range of hundreds of meters from their home reefs, tagged individuals have been observed moving across much greater distances, occasionally in excess of several kilometers.…”

Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach

“…However, further research is needed to determine whether the observed increase in reliance on water column production for fishes on oceanic reefs reflected a dietary switch to a more phytoplanktonbased food web or an increase in the flow of phytoplankton C through the same food webs as on shelf reefs. While our study targeted adult individuals across the entire seascape, previous work has shown that ontogenetic shifts in habitat usage of coral reef fishes can also result in dramatic changes in resource utilization through time and space (Cocheret de la Moriniere et al 2003;McMahon et al 2012). …”

The status of coral reef ecology research in the Red Sea

“…Given a lack of such management in most of the Red Sea, future connectivity research should focus on elucidating general patterns of larval dispersal, gene flow among populations, and linkages among the many types of coastal habitats found in the Red Sea (e.g., snapper migration corridors from coastal wetlands to reefs further offshore; McMahon et al 2012). Such data would be essential to inform the design of marine protected areas, should there be a move to develop them within this region.…”