546 
Fishery Bulletin 95(3), 1997 
■ 
Fort Pierce-Palm Beach, FL (0.80, 0.34) 
O 
Veracruz, Mexico (0.99, 0.84) i 
□ 
Panama City, FL (0.68, 0.21) 
• 
Celestun, Mexico (0.69, 0.65) 
♦ 
GulfPort, MS (0.68, 0.21) 
O 
Dzilam DeBravo, Mexico (0.98, 0.86) 
o 
Grand Isle, LA (0.62, 0.98) 
Q 
Florida Region (0.74, 0.03 1 ) 
▲ 
Galveston, TX (0.91, 0.08) 
1 
Northwestern GOM Region (0.90. 0.68) 
T 
Port Aransas, TX (0.91, 0.02) 
O 
Mexico Region (0.95, 0.0031) 
o 
co 
'oo 
-15 
-16 
-17 
-18 
-19 
o 
§ 
§ 
- 20 “ 
-21 
8 
d 
a 
T 
■ 
o 
♦ 
O 
A 
0 
□ 
B 
Figure 3 
(A) Stable carbon and ( B ) nitrogen isotopic results along the length of a spine for each king mackerel site 
and region. Legend contains r 2 values or carbon and nitrogen isotopes respectively. Whole spines were 
delineated into three sections each (tip, mid, and base). If the spines had more than three divisions for 
analysis, the middle sections were averaged together to create one value. If the spine was divided into 
two sections for analysis, the middle section was excluded for the figure. 
along the individual spines for the sites or regions. 
The data suggest a factor other than change in 
trophic level determines isotopic values found within 
the spines. Numerous factors could influence the 
range and trend of isotopic values found within 
a dorsal spine, such as feeding region, trophic- 
level status of the individual, and the manner in 
which the spine was segmented. 
Stable carbon and nitrogen isotopic values at the 
base of the food chain vary within the Gulf of Mexico 
(Table 1), particularly among waters off southern 
Florida and the northwestern Gulf of Mexico. We 
