Stable isotopic assessment of site fidelity of mummichogs, Fundulus heteroclitus, exposed to multiple anthropogenic inputs

The goals of the study were: (1) to evaluate stable isotopic analysis (SIA) in determining the site fidelity of mummichogs, Fundulus heteroclitus, along a smaller spatial scale (~10 km) in homogenous habitat type relative to previous SIA studies; and (2) to cross-validate SIA results with mark-recapture results from a study conducted concurrently at the same sites in the upper Miramichi River estuary (MRE), New Brunswick, Canada influenced by two pulp mills and three municipal wastewater facilities. Mummichogs sampled at 9 sites along the upper MRE (n = 198) had overall mean (± SD) ratios of −21.03 ± 1.45 ‰ δ13C and 11.37 ± 1.02 ‰ δ15N. Mean δ13C and δ15N ratios were significantly different among sites with mean δ13C increasing in a downstream direction and distinct δ15N group signatures along the northern and southern shores. Multivariate analyses detected seven distinct groups out of nine sites sampled and these differences appear to be related to wastewater treatment influences, thus demonstrating the utility of SIA as a method to determine the site-specificity of organisms on a relatively small spatial scale within homogenous habitat within an estuary. These results, in addition to the scarcity of statistical outliers (3 %) during examination of isotopic ratios within sites support the results of a previous mark-recapture study that demonstrated very few mummichogs (3.4 %) in the upper MRE move more than 200 m.