Figure 1.
Bathymetric and oceanographic setting for Lady Elliot Island, southern Great Barrier Reef.
Schematic map of the southern GBR showing location of LEI, bathymetry (full lines) and typical flow of the East Australian Current (bold arrows). Modified from [68].
Figure 2.
Photographs presenting the three main behaviours for M. alfredi observed around the LEI reef: (A) cruising (manta ray swimming with cephalic lobes rolled and mouth closed), (B) cleaning (manta ray at a ‘cleaning station’, maintaining a near stationary position atop a coral patch for several minutes while being cleaned by cleaner fishes), and (C) foraging (manta ray ram feeding - swimming against the tidal current with its mouth open and sieving zooplankton from the water).
Table 1.
List of explanatory variables used in this study for the period May 2008 to May 2011. Details include source and unit of measure for each continuous variable or category levels for categorical predictors (marked *).
Figure 3.
Generalised additive model output for each manta ray behaviour observed at LEI.
Results for the functional relationships between sightings of cruising, cleaning and foraging M. alfredi per trip around the Lady Elliot Island reef and the set of temporal and environmental predictors. Each column presents a different behaviour and each row presents results for the influence of a predictor to each behavioural activity, where significant. For each plot, the y-axis is a relative scale, and its magnitude reflects the importance of each variable. Dashed lines and error bars represent 95% confidence intervals.
Table 2.
Summary of the generalised additive model for assessing the influence of each predictor to the relative abundance manta rays (M. alfredi) exhibiting cruising, cleaning and foraging behaviour at LEI.
Figure 4.
Sighting trends for cruising, cleaning and foraging manta rays at Lady Elliot Island.
(A) Manta ray sighting records throughout the year for each behaviour; dots indicate data records and full lines show overall temporal trend via locally weighted scatterplot (loess) smoothing. (B) Frequency distributions of numbers of cruising, cleaning and foraging manta rays sighted per trip.
Figure 5.
Habitat use for manta rays at Lady Elliot Island.
Map of Lady Elliot Island showing total observations of M. alfredi at seven sites around the reef, between May 2008 and May 2011. Pie charts indicate percent activity at each site for cruising, cleaning and foraging manta rays. High-resolution image of LEI obtained from the Quickbird orbiting satellite (Geoimage Pty Ltd., www.geoimage.com.au) and data overlaid using ArcGIS 10 (ESRI, www.esri.com/software/arcgis).