Stable Nitrogen Isotopes in Fish: Literature Synthesis on the Influence of Ecotonal Coupling

Stable nitrogen isotopes have customarily been used to delineate trophic position with only infrequent regard to source variability. A compilation of literature data supports a previous tentative hypothesis that marine fish are enriched in15N relative to those inhabiting freshwaters. Estuarine and anadromous fish were also confirmed to have intermediate δ15N values depending on their respective time spent feeding in either fresh- or salt water. The use of fish δ15N as a measure of continental-marine coupling in complex coastal environments will therefore provide additional support for analyses based on the more traditionally utilized isotopes δ34S or δ13C.