masters capstone project paper
TRANSCRIPT
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Thomas Pratt
Marine Conservation and Policy
Title: The Riverhead Foundation: Using necropsies to increase awareness of marine conservation
issues.
Sea turtle biology
Sea turtles have been around for more than 100 million years (Lutz et al. 2002). Today,
there are seven species of sea turtles in existence which includes green sea turtles (Chelonia
mydas), loggerhead sea turtles (Caretta caretta), leatherback sea turtles (Dermochelys coriacea),
olive ridley sea turtles (Lepidochelys olivacea), kemp’s ridley sea turtles (Lepidochelys kempii),
flatback sea turtles (Natador depressus) and hawksbill sea turtles (Eretmochelys imbracata).
There is a myriad of of different things that sea turtles eat. Every sea turtle species is different,
and has its own unique diet. Leatherback sea turtles predominantly consume gelatinous plankton
such as jellyfish and even salps, while green sea turtles are herbivores and eat a diet of mostly
seagrass and algae that even changes their adipose tissue slightly green (Bjorndal 1997,
Mrosovsky et al. 2009). Loggerhead sea turtles have a varied diet depending on their life stage,
and tend to eat prey items such as crustaceans, gastropods, sargassum, jellyfish, and even
terrestrial insects (Bjorndal 1997). In New York State, species of sea turtles that are found
include green sea turtles (Chelonia mydas), loggerhead sea turtles (Caretta caretta), leatherback
sea turtles (Dermochelys coriacea) and kemp’s ridley sea turtles (Lepidochelys kempii).
Many sea turtle diets depend upon their movements and habitat that they are in.
Hawksbill sea turtles (Eretmochelys imbracata) are often pelagic species, yet tend to migrate
towards the shore to forage off of coral reefs and mangroves (Bjorndal 1997). Hawksbill sea
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turtles are omnivores, and forage in seagrass beds and coral reefs for crustaceans, sponges, and
even seagrass and algae (Bjorndal 1997). Green sea turtles (Chelonia mydas) forage in seagrass
beds as adults, and their adipose tissue evens turns a hue of green since they are vegetarians
(Bjorndal 1997). Kemp’s ridley sea turtles (Lepidochelys kempii) forage in sargassum as pelagic
juveniles, yet move closer to the shore as adults and tend to eat crustaceans such as crabs
(Bjorndal 1997). The ridley turtles that were necropsied this summer often had crab and snail
shells, which shows that crustaceans comprise of the majority of their diet. Olive ridley sea
turtles (Lepidochelys olivacea) primarily live in the Gulf of Mexico, and eat a mixture of salps,
fish, crustaceans and molluscs (Bjorndal 1997). Leatherback sea turtles consume gelatinous prey
such as jellyfish and salps, and when necropsied most of their gastrointestinal tract is filled with
decomposed jellyfish. Other than Leatherback sea turtles, many species of sea turtles tend to
move towards coastal regions to forage near coral reefs, seagrass beds, or mangroves (Bjorndal
1997).
Sea turtles are highly migratory marine animals, especially species such as Leatherback
sea turtles which are regarded as one of the most thoroughly distributed reptile species in the
world (Mrosovsky et al. 2009). Leatherback sea turtles are unique in the fact that they don’t have
a hardshelled carapace with scutes, they can be found in temperate and even subarctic waters
due to their enhanced adipose tissue and gigantothermy (Eckert 2006, Mrosovsky et al. 2009).
Leatherback sea turtles are found in New York waters all year round, while other species are
mostly found during the warmer months in the summer for foraging (Wallace et al. 2013). In the
summer months, loggerhead and green sea turtles are found stranded as a result of fisheries
interaction or boat strikes. Recently, the Riverhead Foundation for Marine Research and
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Preservation has been finding many kemp’s ridley sea turtles coldstunned during the winter
from October to March. The Riverhead Foundation is a nongovernmental organization and New
York State’s only marine mammal and sea turtle rescue center. With a mission statement to
“preserve and protect our marine environment through rescue and rehabilitation, research and
education,” the Riverhead Foundation uses scientific research to educate the public about marine
mammals and sea turtle conservation.
Although Leatherback sea turtles can withstand cooler water temperatures due to their
immense size, sea temperatures can have a dramatic effect on all species of sea turtles. Sea
turtles are reptiles that lay eggs that incubate in nests, and are affected by temperature in a few
ways (Davenport 1997). Sea turtle hatchlings will only survive the incubation period in certain
temperature ranges, and the incubation process is even sped up in warmer temperatures
(Davenport 1997). In the final stretch of incubation the eggs are especially sensitive to
temperature, and will primarily hatch only in temperatures 23 to 33oC (Davenport 1997).
Temperaturedependent sex determination (TDSD) is determined in the middle part of of
incubation during embryonic development, with an average of 29oC as the pivotal temperature
(Davenport 1997). At this pivotal temperature is where the sex ratio of female:male sea turtles is
1:1, and as the temperature becomes greater than 29oC male hatchlings become more rare
(Davenport 1997). As the ocean and atmospheric temperatures rise, the threat of altered sex
ratios increases (Janzen 1994). The higher the temperatures during incubation could possibly
mean that more sea turtle strandings will become predominantly female.
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(Davenport 1997)
Objectives
My objectives in this internship with the Riverhead Foundation were to: 1) examine
trends in sex ratios, cause of death, and human impacts by analyzing sea turtle strandings data 2)
learn about sea turtle anatomy firsthand by conducting necropsies and 3) observe and
understand threats to sea turtle species
Sea turtles as keystone species
Sea turtles are a fundamental keystone species in marine ecosystems (Tisdell and Wilson
2002). They help contribute to the balance and maintenance of marine ecosystems that have
biological, economic and cultural significance (Tisdell and Wilson 2002). Essentially, a keystone
species is any species that has a substantially large effect on its ecosystem, comparative to its
abundance (Tisdell and Wilson 2002). Sea turtles have many different roles in marine habitats
that help contribute to the function and stability of its ecosystem. The green sea turtle (Chelonia
mydas) eat sea grass and graze in seagrass beds, which helps that ecosystem become more
productive (Tisdell and Wilson 2002). Hawksbill sea turtles (Eretmochelys imbracata) consume
sponges, which helps conserve the production and diversity of coral reef systems (Tisdell and
Wilson 2002). Not only do sea turtles help maintain diversity to a healthy marine ecosystem, but
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they have a large economic and cultural importance because of it (Lutz 2002). Since these
species are crucial to marine ecosystems, it is important to fully understand them through
scientific research in order to help their conservation status. The Riverhead Foundation
recognizes that these species are crucial to the balance of marine habitats, thus helps rescue and
rehabilitate sick and injured sea turtles back into the marine environment.
Threats
In recent years, ocean ecosystems have gone through a lot of changes, which threatens
many species such as sea turtles with extinction (Halpern et al. 2008). With the increase in sea
temperatures, acidification of the ocean, and pollution of plastic, oil and gas to many marine
habitats, these threats can become detrimental to marine organisms. Human impacts on marine
ecosystems have threatened many species that are vulnerable to extinction (Davenport 1997,
Halpern et al. 2008, Janzen 1994). These impacts take on myriad forms, including activities such
as greenhouse gas emissions, fisheries bycatch, sea surface temperature and direct habitat
degradation (Halpern et al. 2008). With all of the dramatic effects that humans have on global
marine ecosystems, it is important to help recognize this ecological change. Even though the
direct impact that humans have on our marine ecosystems is extensive, we have the ability to
educate others that aren’t aware of sea turtle threats and conservative techniques. The Riverhead
Foundation helps increase conservation awareness by holding lectures, attending fairs and
events, and educating the public. The scientific research done by the Riverhead Foundation helps
contribute to the knowledge and education brought to the public.
Many threats that humans have on sea turtles include fisheries interaction, marine
pollution, habitat degradation, and global climate change. Many Loggerhead and leatherback sea
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turtles have been found to be caught in gillnets, hooked on longline hooks and even caught
incidentally (Lewison et al. 2004). Bycatch from pelagic longlines help represent a significant
portion of the 8095% declines in populations for both Leatherback and Loggerhead sea turtles
(Lewison et al, 2004). Not only are fisheries a substantial threat to the populations of sea turtles,
but marine debris and pollution as well. Numerous Leatherback sea turtles postdeath, have been
found to ingest plastic bags, plastic containers, and even metal hooks (Mrosovsky et al. 2009).
The diet of a Leatherback sea turtle primarily comprises of jellyfish, and unfortunately the
oceans are littered with floating plastics that can look jellyfishlike prey (Mrosovsky et al. 2009).
Both fishing gear, boats and plastic pollutants have a significant impact on the survival of
Leatherback and other sea turtles alike.
Besides direct human impact, one of the main threats to the conservation of sea turtles is
global climate change. Sea turtles are reptiles, where their sex is dependent not on chromosomes
but by the temperature of incubation (Davenport 1997). This fundamental determination could
mean drastic changes in the sex ratio of many species of sea turtles and freshwater turtles alike,
even with a slight increase in centigrade (Janzen 1994). Statistical evidence has shown that with
an average global temperature increase of 4oC would essentially eradicate all future male sea
turtle offspring (Janzen 1994). With the ever changing climate of both the atmosphere and
marine environment alike, the sex ratio of female to male sea turtles will continue to increase.
This dramatic change in sea turtle sex ratios can become a threat to the survival of future sea
turtle populations. By observing the sex of sea turtle strandings over the years, it might be
possible to see if there is a trend towards this altered sex ratio. Every single sea turtle necropsy is
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identified by sex, and stranding data over the years can help scientists determine trends for future
scientific research.
Nongovernmental organizations
Nonprofit or nongovernmental organizations help represent a large sector of the marine
conservation and policy field. The partnership between the government and nongovernmental
organization is crucial since many organizations deal with many marine conservation issues
(Groom et al. 2006). NGOs help address conservation issues such as fisheries management,
scientific modeling, human impacts, and scientific information and education (Groom et al.
2006). Many NGOs such as Greenpeace, Ocean Conservancy, the Marine Conservation Society,
and the Worldwide Fund for Nature strive for and obtain grants for conservation research
(Sutherland et al. 2004). Many conservation issues include habitat management for specific
species, species diversity, and conservation education and outreach through scientific evidence
(Sutherland et al. 2004). Nongovernmental organizations are imperative to the community
because they are the link between the scientific community, the public and the surrounding
environment (Groom et al. 2006).
The Riverhead Foundation for Marine Research and Preservation is an example of a
nonprofit organization that uses scientific research to not only directly help vulnerable marine
species but to educate the public as well. The Riverhead Foundation is New York State’s only
marine mammal and sea turtle rescue and research program. This organization not only helps
rescue marine animals, but rehabilitates them back into shape before releasing them into their
native habitats. Animals that the foundation works with includes cetaceans (whales, dolphins,
porpoises), pinnipeds (seals) and sea turtles. Many seals, dolphins, porpoises, and sea turtles are
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found underfed, injured, weak and infected. Trained biologists and doctors not only rescue these
injured marine animals on the beach, but assist with the rehabilitation process as well. Seals,
dolphins, and sea turtles are all given proper medicine like antibiotics, fed daily to increase fat
reserves and strengthen up the animal until it is ready to be released in the wild. Although
research and education is a big part of the Riverhead Foundation, the rescue and rehabilitation
aspect is the core of the organization.
The Riverhead Foundation deals with marine conservation issues that are involved with
sea turtles. Out of the seven species of sea turtles found throughout the world, the Riverhead
Foundation works with four species that includes green sea turtles (Chelonia mydas), loggerhead
sea turtles (Caretta caretta), leatherback sea turtles (Dermochelys coriacea) and kemp’s ridley
sea turtles (Lepidochelys kempii). Being New York State’s only sea turtle rehabilitation and
rescue center, The Riverhead Foundation for Marine Research and Preservation has the
responsibility to help rescue injured or coldstunned sea turtles in the area. Often in colder
months, many Green and Kemp’s Ridley sea turtles are found cold stunned, a condition in which
their core body temperature becomes too cold for locomotion (Davenport 1997). Often, sea
turtles are found in a comalike state, where their heart rate drops significantly and can even lead
to death if their body temperature reaches 10oC (Davenport 1997). In New York state, these
coldstunned sea turtle comprise of the majority of stranded sea turtles found in the tristate area
due to colder Atlantic waters.
The evidencebased research that the Riverhead Foundation does not only helps the
scientific community such as NOAA fisheries and NMFS, but public education as well. The
main method of scientific research done on stranded sea turtles by the Riverhead Foundation is
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necropsies. If a deceased sea turtle is found on a beach or in a fishing net in the New York area,
the Riverhead Foundation is called in to perform a necropsy. A necropsy is fundamentally a
postmortem dissection analysis done to a sea turtle on its back (Wolke and George 1981). Sea
turtle species are all either vulnerable, endangered or critically endangered in the wild, other than
the Flatback sea turtle (Natador depressus) which is data deficient (Red List Standards 1996,
Wallace et al. 2013). Since their conservation status is so critical, it is imperative to analyze and
understand the cause of death and human impact when stranded.
Methods
The main method with this sea turtle research was using necropsies of stranded sea turtles
in the New York area. Necropsies help scientists to fully understand the cause of death and
threats to these marine species. With any necropsy there are two main steps done: an external
examination and the dissection (Wolke and George 1981). The external examination includes
levelA analysis, which involves measurements of the straight and curved carapace length,
width, plastron length, as well as the weight. Both straight and curved measurements are done for
the carapace length and width, even though straight measurements are favored (Wolke and
George 1981). Other observations are done to check whether there is any fisheries interaction or
evidence of boat strike. The condition of the skin, plastron and carapace is thoroughly examined
in order to gain insight about cause of death or human interaction. A pit scanner is used before
opening up the body cavity to check for evidence of any pit tags as well.
Using a scalpel blade, an incision is made around the nine plastron bones, starting off
right below the head but before the epiplastron bones (Wyneken and Witherington 2001). The
main incision is made following the shape of the plastron bones along the cartilage, and then the
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muscle tissues that connect to the plastron is removed and then the body cavity is opened up.
After the body cavity is opened up the muscle masses over the organs is broken down and moved
out of the way, or held with a blubber or stevedore’s hook for a large sea turtle (Wolke and
George 1981). The organ systems are then analyzed for any significant findings such as
hemorrhaging or blood clots, and the major organs are sampled for further analysis.
(Wyneken and Witherington 2001)
Using numerous tools such as a scalpel blade and pliers, different samples are taken for
further analysis. Samples that are taken include the scutes, muscle tissue, GI tract, adipose tissue,
liver and kidney. Scute samples are analyzed using stable isotope analysis to determine whether
the animal is a more pelagic or coastal species. Muscle tissue is used for frozen sampling as well
as genetic research for the National Marine Fisheries Service. The gastrointestinal tract is
sampled to determine stomach contents of what the turtle was eating such as crabs, molluscs,
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jellyfish, or even nonfood items such as plastic or hooks. The adipose tissue is the fatty tissue
that surrounds the plastron and carapace, and is used for contaminant testing. Similar to adipose
tissue, the liver is taken for toxicology as well to measure for contaminants and organochlorines.
Lastly, the other main sample that is taken is the kidney which is sampled and collected in order
to test for the contamination of heavy metals.
Photo documentation is performed throughout the process of the physical and external
examination, as well as the dissection. A measuring tape with a photo identification card is put in
every picture in order to get an idea of how large the sea turtle is for proper documentation.
Photo documentation of the carapace, plastron, and inside organs are done. In addition, any
anomalies or implementations for cause of death is photo documented such as broken bones,
blood clots and hemorrhaging. The last thing that is photo documented are the gonads (ovaries or
testes) for proper sex determination.
Findings
Out of 36 necropsies done, only 8 were identified as male, 27 were identified as female
sea turtles, and one unknown sea turtle. That representation of female sea turtles is a substantial
75.0%, a male representation of only 22.22%, and 2.78% unknown or cannot be determined.
Below is a data table of all 36 necropsies performed which includes information of significant
findings by species.
Figure 1 Notable findings by sea turtle species
Species
Boat/prop
strike
Nematodes/GI
tract inflammation
Broken
bones/missing
appendages Hemorrhages NSF Plastic
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Dermochelys
coriacea 1 0 1 1 1 1
Caretta
caretta 3 0 1 0 3 0
Chelonia
mydas 0 2 0 1 4 0
Lepidochelys
kempii 1 2 0 0 17 0
Figure 2 is a data table that includes information based on stranding year from 2010 to
2014, as well as the sex identified based on each species of sea turtle. Only one loggerhead sea
turtle (Caretta caretta) was unable to be identified by sex since it was highly decomposed and
the sex organs were not there.
Species 2010 2011 2012 2013 2014 Male Female Unknown
Total
number
Dermochelys
coriacea 0 0 0 0 3 2 1 0 3
Caretta caretta 0 0 0 0 6 1 4 1 6
Chelonia
mydas 0 0 2 3 2 1 6 0 7
Lepidochelys
kempii 1 0 4 13 2 4 16 0 20
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Figure 2 Sex identified and stranding year for each sea turtle species
Figure 3 Sea turtle sex identified
Figure 3 shows a stacked bar graph that depicts the number of males and females
identified for each species. (Left to right) Starting off with the leatherback sea turtle, 2 males and
one female was identified. 4 females, one male and one unknown for the loggerhead sea turtle. 6
females and 1 male for the green sea turtle, and 4 males and 16 females for the kemp's ridleys.
Conclusions
The threat of endangerment of every species of sea turtles is linked to human recreation
and influence (Halpern et al 2008, Janzen 1994). With a substantial amount of female sea turtles
identified of 75.0%, this could signify the threat of global climate change to the survival of sea
turtle species. The ratio of female to male sea turtles that were necropsied through the Riverhead
Foundation for Marine Research and Preservation is 27:8. For every male sea turtle that was
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identified, 3.375 female sea turtles were identified as well. However, this skewed sex ratio is
only a small subset of a larger population of sea turtles in the New York State area. Since these
36 necropsies do not represent the populations in the Northwestern Atlantic Ocean, actual sex
ratios and population size cannot be determined. Samples extracted are being used for NOAA
fisheries, National Marine Fisheries Service, and even with Stony Brook University with
gastrointestinal tract research. Muscle samples preserved in salt and DMSO is used for genetic
research by NOAA fisheries to determine certain distinct populations for certain species of sea
turtles.
The majority of the data found from the necropsies have indications for human impact
through fisheries and pollution. Out of the 36 necropsies, 5 were definite boat or prop strikes,
with an additional three showing chances of fisheries interactions with hemorrhaging and blood
clots found but no definite or substantial evidence. Other than cold stunning, fisheries interaction
through boat strikes is the number one cause of death for sea turtles in the New York area. In this
study, about one out of every seven sea turtles dissected has shown considerable evidence of
fisheries interaction. Additionally, NY50872014 (Dermochelys coriacea) was found not only
with a distinct propellor slice on its carapace, but it had two plastic bags in its stomach. This
conveys the idea that floating plastics can be an immense threat to Leatherback sea turtles
(Lewison et al. 2004, Mrosovsky et al. 2009). Leatherback sea turtles rely on a diet that
comprises of gelatinous plankton such as jellyfish and salps, and floating clear plastics can
undoubtedly pose a threat to this species (Mrosovsky et al. 2009). With the data found in this
scientific research, human impact through climate change, bycatch and fisheries interaction, and
pollution is a distinct threat to the survival of sea turtles.
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With regards to marine conservation, sea turtles are undoubtedly the group of species that
are of most concern due to their conservation status on the IUCN red list of threatened species
(Tisdell and Wilson 2002). All species of sea turtles are at least vulnerable to extinction, with
many being listed as endangered or critically endangered (Tisdell and Wilson 2002). Species that
are listed as vulnerable under the IUCN red list include Olive ridley (Lepidochelys olivacea) and
Leatherback sea turtles (Dermochelys coriacea) (AbreuGrobois & Plotkin 2008, Wallace et al.
2013). Species that are listed as endangered under the IUCN red list include loggerhead (Caretta
caretta) and green sea turtles(Chelonia mydas) (Marine Turtle Specialist Group 1996, Seminoff
2004). Two species are even listed as critically endangered which includes hawksbill
(Eretmochelys imbracata) and kemp’s ridley sea turtles (Lepidochelys kempii) (Marine Turtle
Specialist Group 1996, Mortimer and Donnelly 2008). Since these species are particularly
endangered, threats such as fisheries and human impact can become a distinct problem for their
future populations.
Current and future research is essential for awareness of these endangered species. Every
year, more scientific research is being conducted about sea turtles, including research done by
The Riverhead Foundation. Every year the Riverhead Foundation comprises annual reports about
cetaceans, pinnipeds and sea turtles. In the reports include all of the sea turtle strandings in the
New York State area, which dates back to 1980. In the chart below represents sea turtle
strandings by species from 1980 up to last year. Since 2007, sea turtle strandings have increased
slightly, and the majority of sea turtles that are found are Loggerhead and Kemp’s ridley sea
turtles (DiGiovanni Jr. et al. 2013). By observing the amount of sea turtle strandings and the sex
of sea turtles from the past and years to follow, the threat of climate change can be evaluated.
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This scientific data done by the Riverhead Foundation is published annually and used in lectures
and events to help increase awareness through education.
(DiGiovanni Jr. et al. 2013)
With regards to other research being done, there are many issues being addressed such as
bycatch records, sea turtle diet, nesting habitat, and marine pollution and debris. Bycatch
research is being done through Duke Marine Laboratory and Blue Ocean Institute through Stony
Brook University (Lewison et al. 2014). Certain bycatch hotspots for many marine megafauna
such as sea turtles have been identified, and can assist in bycatch management from gear type
and migration routes (Lewison et al. 2014). Species such as loggerhead and leatherback sea
turtles are threatened due to pelagic longlines and fisheries bycatch, therefore studied like this is
important for the future of sea turtles.
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There is a variety of research being done on sea turtle diet and habitat. One current study
uses stable isotope analysis through the use of scute and epidermis samples (Vander Zanden et
al. 2014). This study is using stable isotope analysis to determine the habitat and diet of sea
turtles through isotopic composition (Vander Zanden et al. 2014). It is possible through current
research like this, to help determine migration routes of loggerhead sea turtles through diet and
habitat use (Vander Zanden et al. 2014). By knowing what and where a sea turtle forages, we
will know what marine areas to manage and protect.
Other current research includes analysis of marine debris ingested such as plastic debris.
Presentday research has shown that out of the seven species of sea turtles, leatherback
(Dermochelys coriacea) and green (Chelonia mydas) sea turtles are the species that ingest the
most marine debris (Schuyler et al. 2014). Since green sea turtles are herbivores and leatherback
sea turtles are gelatinous planktivores, marine debris poses a considerable risk to these species
(Schuyler et al. 2014). By knowing what marine debris is often found ingested in these animals
through necropsies, we will know what kinds of pollutants such as plastic to regulate. Since sea
turtles are highly migratory, pelagic species, the majority of research that has been done is recent
due to the establishment of modernday technologies. The future of sea turtles may rely on the
current conservation research being done, and the action to counteract the effect of human
impact is just as crucial. The current research on sea turtles, including sea turtle strandings could
potentially help the management and conservation of future sea turtle populations.
References
AbreuGrobois, A & Plotkin, P. (IUCN SSC Marine Turtle Specialist Group) 2008. Lepidochelys olivacea. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 12 August 2014.
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Bjorndal, K. A. (1997). Foraging ecology and nutrition of sea turtles. The biology of sea turtles, 1, pp. 199231. Davenport, J. (1997). Temperature and the lifehistory strategies of sea turtles. Journal of thermal biology, 22(6), pp. 479488. DiGiovanni Jr., R., Durham, K., DePerte, A., Ferina, D. The Riverhead Foundation for Marine Research and Preservation Annual Report. (2013). Web. 21 August 2014. <http://www.riverheadfoundation.org/pubfiles/annualreports/2013Report.pdf> Eckert, S. A. (2006). Highuse oceanic areas for Atlantic leatherback sea turtles (Dermochelys coriacea) as identified using satellite telemetered location and dive information. Marine Biology, 149(5), pp. 12571267. Groom, M. J., Meffe, G. K., & Carroll, C. R. (2006). Principles of conservation biology (pp. 174251). Sunderland: Sinauer Associates. Halpern, B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F., D'Agrosa, C., ... & Watson, R. (2008). A global map of human impact on marine ecosystems. Science, 319(5865), pp. 948952. Janzen, F. J. (1994). Climate change and temperaturedependent sex determination in reptiles. Proceedings of the National Academy of Sciences,91(16), pp. 74877490. Lewison, R. L., Freeman, S. A., & Crowder, L. B. (2004). Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles. Ecology letters, 7(3), pp. 221231. Lewison, R. L., Crowder, L. B., Wallace, B. P., Moore, J. E., Cox, T., Zydelis, R., ... & Safina, C. (2014). Global patterns of marine mammal, seabird, and sea turtle bycatch reveal taxaspecific and cumulative megafauna hotspots.Proceedings of the National Academy of Sciences, 111(14), pp. 52715276. Lutz, P. L., Musick, J. A., & Wyneken, J. (Eds.). (2002). The biology of sea turtles (Vol. 2). CRC press. Marine Turtle Specialist Group 1996. Caretta caretta. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 12 August 2014. Marine Turtle Specialist Group 1996. Lepidochelys kempii. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 12 August 2014. Mortimer, J.A & Donnelly, M. (IUCN SSC Marine Turtle Specialist Group) 2008. Eretmochelys imbricata. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 12 August 2014.
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Mrosovsky, N., Ryan, G. D., & James, M. C. (2009). Leatherback turtles: The menace of plastic. Marine Pollution Bulletin, 58(2), pp. 287289. Red List Standards and Petitions Subcommittee 1996. Natator depressus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 06 August 2014. Seminoff, J.A. (Southwest Fisheries Science Center, U.S.) 2004. Chelonia mydas. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 12 August 2014. Schuyler, Q., Hardesty, B. D., Wilcox, C., & Townsend, K. (2014). Global analysis of anthropogenic debris ingestion by sea turtles. Conservation Biology, 28(1), pp. 129139. Sutherland, W. J., Pullin, A. S., Dolman, P. M., & Knight, T. M. (2004). The need for evidencebased conservation. Trends in Ecology & Evolution, 19(6), pp. 305308. Tisdell, C., & Wilson, C. (2002). Ecotourism for the survival of sea turtles and other wildlife. Biodiversity & Conservation, 11(9), 15211538. Vander Zanden, H. B., Tucker, A. D., Bolten, A. B., Reich, K. J., & Bjorndal, K. A. (2014). Stable isotopic comparison between loggerhead sea turtle tissues. Rapid Commun. Mass Spectrom, 28, pp. 16. Wallace, B.P., Tiwari, M. & Girondot, M. 2013. Dermochelys coriacea. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 06 August 2014. Wolke, R. E., & George, A. (1981). Sea turtle necropsy manual. US Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Center, Panama City Laboratory, pp 120. Wyneken, J., & Witherington, D. (2001). The anatomy of sea turtles (p. 172). Southeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, US Department of Commerce. pp. 152.