4 | RESULTS
From each period we were able to obtain tissue for
δ13C and δ15N analysis from six San
Juan River fishes. Sample sizes for each species were smaller for the
historical (n range = 6 – 13) compared to the contemporary period (n
range = 23 – 385) but the size range of each species sampled was
similar (Table 1). Overall, the global mean δ15N of
fishes increased from 9.36‰ (SD = 1.35) to 12.76‰ (SD = 1.43) between
periods (Figure 2). Mean δ13C of fishes demonstrated
less change with the historical mean of -22.67‰ (SD = 1.33) compared to
the contemporary mean of -22.74‰ (SD = 0.96).