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Loggerhead Problems Nesting habitat destruction Human lighting directing hatchlings away from ocean Turtles caught in fish nets Population declining
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Saving the Loggerheads
By Brian Vajanaphanich and Sean Wang
Loggerhead Background
• Most abundant marine turtle in the U.S.• Live from 47-67 years• Grow up to 3 feet• Females lay ~80 eggs/year• Females start laying eggs at 22
Loggerhead Problems
• Nesting habitat destruction• Human lighting directing hatchlings away from
ocean• Turtles caught in fish nets• Population declining
?????
Loggerhead Options
• Maintaining nesting habitat• Implementation of Turtle Excluder Device on
fish nets
Loggerhead Egg Saving
• Egg mortality rates can sometimes reach 95%• Human affects on turtles cause babies/eggs to
– Crawl the wrong way when trying to enter the water for the first time
– Be crushed under human activity on beaches• The average mortality rate for turtle babies
and eggs is ~32.53%
Loggerhead TED
• Tens of thousands of turtles per year are killed by bottom trawling fishing nets
• The main victims of fishing nets are turtles aged between 9-16 years old
• TEDs(Turtle Exclusion Devices) allow turtles to pass through fishing nets without being trapped and killed
Loggerhead Simulation
• Leslie matrix used to model population• Estimated 55 year survival
Age(Years)
Survival Rate(%/year)
Fecundity(Eggs/year)
1 .6747 0
2-8 .7857 0
9-16 .6758 0
17-22 .7425 0
23-55 .8091 80
Loggerhead Population
• Under current conditions the population is expected to drop by ~3% annually
Eigenvalues/Eigenvectors
• When a square matrix is multiplied by a vector, the resulting vector is a scalar multiple of the original vector
• There are as many possible eigenvalues as the number of rows and columns in the matrix
• Eigenvalues>1 show growth, <1 show death
Loggerhead R Coding
• Created a 55 by 55 matrix that updated the population vector.
• Graphed the population over time• Calculated and graphed the eigenvalue at
different survival rates
Loggerhead Option 1
• We can increase the survival rate of 0-1 year olds (eggs/babies)
Loggerhead Option 2
• We can increase the survival rate of 9-16 year olds by implementing TEDs
Loggerhead Solution• If TEDs can raise the survival rates of 9-16 year
olds by at least ~6.6% then the Loggerhead Turtles will be saved.
Loggerhead TED Talk
• TEDs are estimated to reduce mortality rates from trawling nets by 97%
• Only reduces shrimp catch by 5-13%• Relatively cheap to implement.
High Fives Only!!!!!
Acknowledgements• Crouse, Deborah T., Larry B. Crowder, and Hal
Caswell. "A Stage-Based Population Model for Loggerhead Sea Turtles and Implications for Conservation." Ecology 68.5 (1987): 1412-423. Jstor. Ecological Society of America, 07 Apr. 2008. Web. 30 July 2015.
• Shiffman, David. "Turtle Excluder Devices: Analysis of Resistance to a Successful Conservation Policy." Southern Fried Science. Southern Fried Science, 07 Jan. 2011. Web. 30 July 2015.
• William Cuello, Robert Guy, Timothy Lewis, Sebastian Schreiber, King David, and William Cuello
https://www.youtube.com/watch?v=jRFaEYn2fOc&feature=youtu.be
Turtle Movie
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