Fig 1.
Study area for aerial surveys.
Map includes an (a) inset of the United States of America and (b) the state of Florida showing the region for this study. Hatched area indicates extent of the survey area over which aerial surveys were conducted. Dotted lines representing the core of the Florida Current are meant as approximations for reference. Source: ArcWorld Supplement, Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute.
Fig 2.
Seasonal sightings of sea turtles from aerial surveys conducted in 2011–2012.
Each symbol represents a single sea turtle. Dotted lines represent the approximate location of the core of the Florida Current. Source: Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute.
Fig 3.
Sightings of the two most commonly observed sea turtle species in 2011–2012 by season.
Loggerheads (top panels) and green turtles (bottom panels) sighted in each season during 2011–2012 aerial surveys. Note that the highest numbers of loggerheads sighted is in the spring while the highest numbers of green turtles sighted is in the summer. Each symbol represents a single sea turtle. Dotted lines represent the approximate location of the core of the Florida Current. Source: Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute.
Table 1.
Summary of combined aerial survey effort (km), the number of sea turtles sighted (n), seasonal estimates of sea turtle density (turtles/km2) and abundance with 95% confidence intervals for each estimate including lower and upper confidence limits (LCL and UCL, respectively).
Seasons are defined as winter (December-February), spring (March-May), summer (June-August), and fall (September-November).
Fig 4.
Plot of the detection function for sea turtles based on the AIC selected Conventional Distance Sampling (CDS) model.
Histogram represents the probability of detection for each distance interval. The curved line is the detection function, showing the probability that a turtle is observed as a function of distance from the transect line.
Table 2.
Akaike’s Information Criterion (AIC) values for the conventional distance sampling and multiple covariate distance sampling models of the detection function tested.
Fig 5.
Seasonal trend in sea turtle surface density with 95% confidence intervals estimated from conventional distance sampling analysis of aerial surveys.
Turtle densities varied with season in both years. The large peak in spring 2012 corresponded with a larger than normal number of nesting loggerhead turtles.