MacAvory et al.: Anadromous fish as marine nutrient vectors 
167 
Figure 1 
The boxed area indicates the section of the Rappahannock River, Virginia, between the towns of Fredericksburg 
and Tappahannock, where all fish were captured to determine the role of anadromous fish as marine nutrient 
vectors to the freshwater environment. Boat electrofishing was conducted between February and May 1997 and 
1999. Sampling was conducted so that fish were captured before, during and after the spring spawning run of the 
anadromous Alosa spp. 
The isotope compositions are reported in relation to 
standard material and follow the same procedure for all 
stable isotopic measurements, as follows: 
&E = [( JC £/>'£ , )sample/(' : £'/>'J5)standard] - 1) x 1000, (1) 
where E = the element analyzed (C, N, or S); 
x = the molecular weight of the heavier isotope; 
and 
y = lighter isotope te=13, 15, 34, and y=12, 14, 
32 for C, N, and S, respectively). 
The standard materials to which the samples are com- 
pared are Pee Dee Belemnite for carbon, air N 2 for 
nitrogen, and Canyon Diablo Triolite for sulfur. Repro- 
ducibility of all measurements was typically 0.2 %c or 
better. Between every 12 samples, a laboratory standard 
was analyzed. In a typical run of 60 samples (+5 stan- 
dards, 65 measurements total) the standard deviations 
for d 15 N and 6 13 C were <0.2%e. For <5 34 S, standard devia- 
tions were <0.3 %o. 
Gas chromatograph-mass spectrometer (GC-MS) 
Once dried, muscle samples selected for compound 
specific isotope analysis (CSIA) were lipid extracted 
(Soxhlet method from Ballentine et ah, 1996) and the 
fatty acids had a methyl group added to the carboxyl 
end (derivitized) so they could be characterized by gas 
chromatography (GC). This was done by heating with 
BF 3 CH 3 OH for eight minutes (Ballentine et al., 1996). 
The fatty acid methyl esters (FAME) were analyzed by 
GC-MS using a Hewlett Packard 5890 Series II gas 
chromatograph (Palo Alto, CA) interfaced to a Hewlett 
Packard 5971A mass sensitive detector (Palo Alto, CA), 
with helium gas as the carrier. A 60-meter J&W DB-5 
