4 
Joseph W. Smith 
cruises between Cape Lookout, North Carolina, and northern Florida, 
research trawls in lower Chesapeake Bay, and port agents in South 
Carolina and northeast Florida. 
Whole cobia were weighed to the nearest 0.1 kg. Carcasses and 
whole cobia were measured for total (TL) and fork length (FL) in 
centimeters and sexed. Gonads were staged for maturity based on criteria 
in Waltz et al. (1979), then excised and weighed to the nearest gram. 
Subsamples of fresh gonadal tissue from 99 cobia were preserved in 
10% buffered formalin, and later sectioned by standard histological 
techniques (Humason 1972) to verify maturity staging in the field. 
A gonadosomatic index ( gsi ) was computed for sexually mature specimens, 
whereby gsi = (gonad mass/body mass) x 100. Axial skeletons were 
missing from some frozen specimens, as catches were “steaked” versus 
filleted. Fork lengths for fish lacking an axial skeleton were estimated 
by calculating a regression of FL on intraorbital distance (measured 
with a caliper in mm) from whole fish (Table 1). Fork length was 
then assigned to carcasses based on this regression. 
Table 1. Mass-length (In) and length-length regression equations for cobia from North 
Carolina and adjacent waters, 1983-94. 
Variables 3 Sex b 
n 
Equation 
R 2 
Range 
W-FL 6 
86 
log W=3.4 log FL -13.3 
0.972 
0.5-32.0 kg 
9 
94 
log W=3.2 log FL -12.3 
0.949 
0.7-32.2 kg 
6 + 9+1 
194 
log W=3.4 log FL -13.0 
0.987 
0.5-32.2 kg 
TL-FL 6 
105 
TL=1.1 FL -1.1 
0.989 
39-136 cm FL 
9 
97 
TL=1.1 FL +0.7 
0.993 
44-142 cm FL 
6 + 9 + 1 
217 
TL=1.1 FL -0.9 
0.995 
39-142 cm FL 
FL-IO 6 
75 
FL=0.8 IO + 17.3 
0.929 
39-136 cm FL 
9 
65 
FL=0.8 IO + 18.5 
0.956 
44-142 cm FL 
a W = fish mass in kg, 10 = intraorbital distance in mm, FL and TL in cm. 
b I = undifferentiated specimens. 
Stomachs were examined and the contents were preserved in 10% 
formalin and later transferred to 50% isopropanol. Bait or chum (fish 
that had obviously been sliced or cut by anglers, mostly Atlantic menhaden, 
Brevoortia tyrannus, pinfish, Lagodon rhomboides, and various sciaenids) 
occurred in 37 stomachs; these items were eliminated from any analyses, 
as were 15 stomachs where bait or chum was the only food item 
