Home Range and Habitat Use of Juvenile Green Sea Turtles (Chelonia Mydas) in Brewers Bay, St. Thomas, USVI
Author: Kari Gehrke
Publisher:
Published: 2017
Total Pages: 48
ISBN-13:
DOWNLOAD EBOOKGreen turtles living in coastal foraging areas often occupy distinct home ranges within which they visit resting and foraging sites. Knowledge about the size of home ranges and movement patterns within these areas is important for sea turtle conservation. However, few data are available for the wider Caribbean. This study measured the movement pattern of five juvenile green sea turtles in Brewers Bay, St. Thomas, in the US Virgin Islands. Each turtle was fitted with a V13 acoustic transmitter and tracked from 90 to 214 days. Turtles were tracked with a fixed array of 30 acoustic receiving stations placed ~200-260 meters apart throughout Brewers Bay. Minimum convex polygon (MCP) and kernel density estimator (KDE) techniques were used to measure home range size. Home ranges were split into days vs. night times and compared by using utilization distributions (UD). Habitat classification was done in areas of high turtle activity and overlapped with home ranges. A general linear model was used to explore the relationship between the home range size (95% UD), core area size (50% UD), and potential predictors: mass. Average KDE day home range size was 63.3 Ha and average day core area was 6.9 Ha. Average KDE night home range size was 35.9 Ha and average night core area was 5.1 Ha. All five incremental area plots became asymptotic, indicating that the home range estimates are robust. There was a statistically significant relationship between core area size and predictor variable (P-value= 0.002; mass). Tracking results showed that all five turtles remained in Brewers Bay for 98% of the tracking duration. During the day turtles were located in seagrass beds and at night they moved to resting areas associated with natural and artificial coral reefs. Core areas for foraging overlapped with seagrass beds dominated by Syringodium filiforme; turtles occurred less frequently in seagrass beds with the invasive Halophila stipulacea. During the night there is less activity when compared to day time hours. Our data confirm that Brewers Bay is an important foraging and resting habitat for juvenile green sea turtles and that their foraging movements center on areas with S. filiforme. These areas in return should receive focused management for both seagrass and reefs to protect green sea turtles. With this management these areas should receive protection from recreational boaters and tourists to prevent the spread of the invasive H. stipulacea