Somatic growth function for immature 
Boggerhead sea turtles, Caretta caretta, 
in southeastern U.S. waters 
Karen A. Bjorndal 
Alan B. Bolten 
Archie Carr Center for Sea Turtle Research and Department of Zoology 
University of Florida 
P.O.Box 118525 
Gainesville, Florida 32611 
E-mail address (for K. A. Bjorndal); kab@zoo.ufl.edu 
Biological Resources Division 
U.S. Geological Survey— Padre Island National Seashore 
PO. Box 181300 
Corpus Christi, Texas 78480 
Abstract-The Sea Turtle Stranding 
and Salvage Network, coordinated by 
the National Marine Fisheries Service 
through a network of state coordinators, 
archives data on sea turtles that strand 
along the U.S. coast. We conducted 
length-frequency analyses, using MUL- 
TIFAN software, to generate somatic 
growth functions for loggerhead sea 
turtles, Caretta caretta , that stranded 
along the Atlantic coast of Florida 
(n = 1234) and along the U.S. coast of 
the Gulf of Mexico (n= 570) between 
1988 and 1995. In both regions, the size 
range of loggerhead sea turtles between 
the size at which they begin to recruit 
in substantial numbers from pelagic 
to neritic habitats (46 cm curved cara- 
pace length [CCL] ) and minimum size 
at sexual maturity (87 cm CCL) was 
composed of 20 year classes and had 
similar von Bertalanffy growth func- 
tions. Our estimates of 20 year classes 
fall within the range of estimates cal- 
culated from previous studies (9 to 29 
years) for this life stage. Because survi- 
vorship in this size range has been iden- 
tified as critical for population recovery, 
an accurate estimate of life stage is 
essential for developing effective man- 
agement plans. 
Manuscript accepted 3 November 2000. 
Fish. Bull. 99:240-246 (2001). 
Bruce Koike 
Aquarium of the Americas 
1 Canal Street 
New Orleans, Louisiana 70130 
Barbara A. Schroeder 
Office of Protected Resources, 
National Marine Fisheries Service, NOAA 
1315 East West Highway 
Silver Spring, Maryland 20910 
Donna J. Shaver 
Wendy G. Teas 
Wayne N. Witzell 
Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
75 Virginia Beach Drive 
Miami, Florida 33149 
Somatic growth functions are critical 
parameters for understanding the life 
history of a species and for developing 
management plans for wild popu- 
lations. Substantial effort has been 
invested in — and considerable infor- 
mation on growth rates has been 
gained from — mark-recapture studies 
of sea turtle populations (Chaloupka 
and Limpus, 1997; Chaloupka and 
Musick, 1997; Limpus and Chaloupka, 
1997; Bjorndal et ah, 2000). Although 
growth studies based on mark and 
recapture of individual animals yield 
direct measures of growth rates, sea 
turtles have characteristics that make 
them relatively poor candidates for 
mark-recapture studies. Sea turtles are 
relatively slow growing; consequently 
mark-recapture studies are long-term 
labor-intensive efforts. The probability 
of recapturing marked individuals is 
low in many populations because of 
the long-range movements and obscure 
migratory patterns in some lifestages 
(e.g. posthatchlings in a pelagic habi- 
tat), high natural mortality in young 
lifestages, and high human-induced 
mortality in juvenile and adult life- 
stages. 
