A recent paper by Joel M. Harding and John D. Reynolds found that the stable isotope ratios of Dungeness crab (Metacarcinus magister) are greatly affected by not only upstream salmon density but also by upstream watershed size and red alder (Alnus rubra), a nitrogen-fixing tree. There were also larger crabs found below the largest estuaries.
The authors write: “These results confirmed that resource subsidies can constitute large proportions of the Dungeness crab’s diet, that crab abundance is determined by habitat size, but that crab size is affected by the magnitude of terrestrial resource influx.”
Find the paper here: Harding, J. M. and J. D. Reynolds. 2014. From earth and ocean: investigating the importance of cross-ecosystem resource linkages to a mobile consumer. Ecosphere. 5(5): Article 54.