Parasite communities indicate effects of cross-shelf distributions, but not mesoscale oceanographic features on northern California Current mid-trophic food web

Research was conducted as part ofthe US GLOBEC Northeast Pacific program and was jointlyfunded by NOAA and the National Science Foundation.This is contribution number 720 of US GLOBEC.

To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work.

Mesoscale physical oceanographic features, such as jets and eddies, can influence the structure of marine ecosystems. We used trophically transmitted parasite communities of pelagic fishes in the northern California Current to examine effects of physical oceanographic features on pelagic ecosystem structure. We tested the hypotheses that (1) oceanographic features associated with a coastal promontory, Cape Blanco, Oregon (USA), produced a faunal break resulting in different pelagic ecosystems north and south of the cape, and that (2) the use of biological hotspots in the area by pelagic nekton is reflected in the trophic interactions of mid- and upper trophic level fishes. We recovered 19 taxa of trophically transmitted parasites from 10 common pelagic fish species caught between Newport, Oregon, and Crescent City, California. Non-metric multidimensional scaling of parasite communities reflected a trophic structure among these fish species; results were similar to published diet studies. We found no evidence in the trophically transmitted parasites of spatial differences between the pelagic ecosystems north or south of Cape Blanco, or within versus outside of the biological hotspots. However, we found significant cross shelf differences in parasite communities. Therefore, Cape Blanco does not seem to be a strong faunal boundary, rather the strongest influence is cross-shelf transport associated with coastal upwelling.