INJURY ASSESSMENT OF SEA TURTLES
UTILIZING THE NERITIC ZONE OF THE SOUTHEASTERN UNITED STATES

April D. Norem

anorem@usgs.gov

¹Coastal Ecology and Conservation Research Group
 

The information provided on this page should be cited as follows:
Norem, A. D. 2005. Injury assessment of sea turtles utilizing the neritic
zone of the southeastern United States. M.S. Thesis, University of Florida,
Gainesville, Florida, USA. 112pp.

PDF Thesis Link: http://etd.fcla.edu/UF/UFE0013282/norem_a.pdf

Presented at the FlSC Strategic Review in St. Petersburg, Florida, May 9-12, 2006,
and the 26th Annual Symposium on Sea Turtle Biology and Conservation.
Island of Crete, Greece, 3-8 April 2006

INTRODUCTION

Injury identification has been used across several taxa (e.g., reptiles, zooplankton, and marine mammals) to gain insight into threats that may be impacting imperiled wildlife populations^1,2,3,4,5. However, one question that has rarely been researched is the effects of non-lethal injuries on an organism's ability to function and reproduce throughout its' lifetime⁶. This is an especially important concern when individuals in early life stages sustain permanent injuries that may reduce their ability to function through their lives such as predator avoidance and reproductive success.

With the vast number of sea turtle research programs being implemented globally, data sharing can sometimes be a trivial objective due to methodological and observer differences. In this study, a standard injury identification system that could be applied across research projects was identified as a crucial missing component in the field of sea turtle injury assessment.

		Develop a systematic Sea Turtle Injury Identification System (STIIS), which researchers could use to determine types and causes of injuries and consistently record injury location.
		Apply the STIIS created in Objective 1 to new and historical sea turtle capture data at the St. Lucie Nuclear Power Plant (SLNPP).
		Quantify types, causes, and locations of injuries found on the sea turtles entrained at SLNPP.      Compare types and causes of injuries among species, size-class and sex-class.

METHODS

STUDY SITE

The St. Lucie Nuclear Power Plant (SLNPP) is located on Hutchinson Island on the east coast of Florida, USA. The SLNPP has three large diameter (3.6 m - 4.9 m) intake valves that extend 365 m offshore, which draw cool water into the plant from the Atlantic Ocean.

FIELD

Turtles were captured, processed (i.e., application of tags, collection of morphological measurements and notation of any injuries/abnormalities) and released into the adjacent coastal waters ~800 m from the intake sites.

LABORATORY

This project was limited to the types and causes of injuries present on the sea turtles utilizing the neritic zone of the southeastern United States and entrained at the SLNPP (Fig 1).

• Barnacle
• Shark
• Social interactions among turtles
• Boat propeller strike
• Fishing (hook & line entanglement)
• SLNPP Intake-pipe related
• Tar
• Unknown
• A Sea Turtle Injury Identification System  (STIIS) was developed from data collected May through December 2000.
• Diagrams were sectioned based on biological and ecological criteria [e.g., bone/ joint location, claw location, flexion zones of the rear flippers, and the standardized placement of both (PIT) and external tags].
• Turtle captures were evaluated for types, causes, and locations of injuries by close examination of each turtle's corresponding field datasheet and photographs.
• Injury causes were identified by characteristic markings/wounds (cues) of each injury type.
• q Each injury was evaluated using the STIIS and entered into a Microsoft Excel spreadsheet.
• Non-descriptive injuries were classified as unknown.
• A Loughlin Scherer (LS) permutation and a naïve chi-square test were used to test for significant differences (associations) in the causes of injury found among species, size-class, and sex-class.
• Injury causes were not counted more than one time per Turtle Id (thus avoiding pseudoreplication).

RESULTS

MAY THROUGH DECEMBER 2000

• 511 turtles (including recaptures) were captured during the 8-month time period (26.2-106.8 cm SSCL).
• Proportion of each injury cause (Fig. 1)
• Injury type was not independent of species or size class (P=0).
• 858 injury location records were found on the 511 captures (Table 1).

Figure 1. Proportion of each injury cause found on the 511 turtles
captured May through December 2000 at the SLNPP.

Table 1. Injury location records (n=858) found on the 511 turtles
captured May through December 2000.

MAY 2000 THROUGH JULY 2004

• 3,290 turtles (2,632 individual turtles) were captured during the 51-month period (Table 2).
• 80% (n=2,532) were classified as new captures, while 23% (n=758) were recaptures.

Table 2. Size-class distribution for sea turtles (n=3,290)
captured at SLNPP May 2000 through July 2004.

FLIPPER AMPUTATIONS

• 3.1% (n=81; 59 loggerhead and 22 green) of the 2,632 individual turtles were found to have equal to or greater than half of one or more of their flippers missing (Fig. 4 & Fig. 5).
• 72 were the result of an unknown cause and 9 were shark-related.

Figure 4. Frequency of flipper amputations by numerical regions
within loggerheads (males, females, and unknown sex categories)

Figure 5. Frequency of flipper amputations by numerical regions
within greens (males, females, and unknown sex categories)

BOAT PROPELLER STRIKES

• 1.9% (n=49; 42 loggerheads and 7 greens) of the 2,632 individual turtles were found with boat propeller strikes.
• Loggerheads were injured significantly more in subregion 2a (rear left section) of the carapace than green turtles (P=0.031).
• Greens were injured significantly more than loggerheads in the anterior portion subregion 2cd of the carapace (p=0.012) (Table 3).

Table 3. Percentage of turtles of each species found with boat propeller
strikes within the anterior and posterior subregion of the carapace.

DISCUSSION & SIGNIFICANCE

Conservation of sea turtle species demands the identification of both lethal and non-lethal threats across the various species, life stages, and sex-classes. The sea turtle injury identification system (STIIS) developed in this project was an integral component in identifying and quantifying injury types, locations, and causes found on the sea turtles at the SLNPP.

		Is there significance in a turtle surviving to adulthood if it cannot reproduce due to a handicap resulting from a prior injury? For example, what would happen to nesting success if 100% of female sea turtles were missing one or both rear flippers?
		Flipper ID tags are the single most important tool used to identify turtles in subsequent captures. Results from this project indicate that the flippers incur significantly higher rates of injury than the neck region. As a result, it is highly recommended that programs explore the idea of standard placement of PIT tags in the dorsal neck region with the objective of increasing tag retention rates and long-term ID of individual turtles. This is particularly important in programs relying on a single tag for identification during recaptures.
		Differences in injury types, causes, and locations were found among species, size-class and sex-class. Such differences further warrant the necessity of direct behavioral observation of turtles in the wild.
		Green turtles were found with higher rates of rear flipper amputations and higher rates of boat propeller strikes on the front of the carapace than loggerhead turtles. Are there behavioral differences in predator avoidance/escape between the species?
		The short and long-term impacts of non-lethal injuries on sea turtles are poorly understood, but the implementation of the STIIS in projects assessing both live and dead turtles would allow for valuable insight into the types, sources, and locations of injuries within each species, size-class and sex-class, allowing for a deeper understanding of the impacts of each injury source. Such crucial information is currently missing from life history models, and may be limiting the ability of such models to predict accurate survival rates.

ACKNOWLEDGMENTS

Foremost, I am extremely grateful to R.R. Carthy & E.R. Jacobson for serving on my committee. I also thank M.Bresette, R. Herren and D. Singewald for their hard work, collaboration and hospitality and I appreciate the support and commitment of Quantum Resources, SLNPP and FP&L. I would also like to thank the International Sea Turtle Symposium. Photographs are credited to FP&L .

LITERATURE CITED

1. Schoener, T.W. 1979. Inferring the properties of predation and other injury-producing agents from injury frequencies. Ecology 60:1110-1115.
    
2. Murtaugh, P.A. 1981. Inferring properties of mysid predation from injuries to Daphnia. Limnology Oceanography 26:811-921.
    
3. Heithaus, M.R. 2001. Shark attacks on bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia; attack rate, bite scar frequencies, and attack seasonality. Marine Mammal Science 17:526-539.
    
4. Heithaus, M.R., A. Frid, and L.M. Dill. 2002. Shark-inflicted injury frequencies, escape ability, and habitat use of green and loggerhead turtles. Marine Biology  140:229-236.
    
5. Shimada, K. and G.E. Hooks III. 2004. Shark-bitten protostegid turtles from the upper  cretaceous Mooreville Chalk, Alabama. J. Paleontology 78:205-210.
    
6. Nakaoka. M. 2000. Nonlethal effects of predation on prey populations; predators mediated change in bivalve growth. Ecology 81(4):1031-1045.
    
7. Loughin, T.M., and P.N. Scherer. 1998. Testing for association in contingency tables with multiple column responses. Biometrics 54:630-637.