Kateri Harrison (email:  kharris@sfsu.edu)

Abstract

Food webs have been hypothesized to have robust structural constraints including:
1.    short food chain lengths
 2.    constant connectance
 3.    fixed predator to prey ratios
 4.    scale dependent proportions of top, intermediate, and basal species

My collaborators as the U.S. Geological Survey are engaged in a semi-quantitative sampling of aquatic invertebrates for 14 streams in the Santa Clara Valley.  They have identified approximately 250 separate taxa in these streams.  I am going to use these data, along with other data about fish taxa, to explore mechanisms potentially responsible for food web patterns.  For example, some ecologists have suggested that dams and altered flow regimes may affect food chin length.  However, the role of disturbance as a mechanism affecting food web structure is not yet clear.  This project will test this and other hypotheses.  This project is also aimed at generating additional hypotheses by comparing and contrasting the structural characteristics of these 14 stream food webs with each other, with stream food webs form other regions, and with other, different ecological systems.  One of this study's most outstanding strengths is the consistent sampling and analytical methods used for construction of food webs.