Research Interests

Pacific coast rockfish ecosystem interactions and the effects of over fishing on these ecosystems. I am examining two major questions as part of my research:

1) What is the effect of the removal of one species of rockfish on the rest of the ecosystem? Are species ÒreplaceableÓ with other species that may be functionally synonymous?

2) Do the functional roles of species of rockfish shift as environmental regimes shift?

In order to examine these questions I am specifically looking at two common species of rockfish Sebastes carnatus (gopher rockfish) and Sebastes chrysomelas (black and yellow rockfish). These species are very closely related, differing primarily in color morphology. Resource partitioning between these two species is spatial; this aids in reducing competitive interactions for food resources. It has been shown experimentally that when black and yellow rockfish are removed from an ecosystem, gopher rockfish will occupy the more desirable territory formerly held by the black and yellow (Larson 1980). Over fishing in certain areas of California may have lead to a similar removal and this phenomenon along with other differences in basic habitat structure may lead to differing functional roles in various regions of the California Current system. I will determine the trophic positions of these fishes using both stomach content and radioisotope analysis of specimens taken from northern, central and southern California. In addition, in order to theoretically explore the longer-term effects of the removal of one of these species on the ecosystem itself I am using an ecosystem model, employing the Ecopath/ Ecosim mass balance modeling technique.

References

Larson, R. J. (1980). Competition, habitat selection, and the bathymetric segregation of two rockfish (Sebastes ) species. Ecol.Monogr. 50, 221-239.