Changes in the expressed protein complement of rainbow trout livers have been studied using a proteomics approach. This report details the alterations of individual protein abundance in the livers of trout that have been subjected to dietary manipulations. These dietary changes have direct and indirect effects on protein turnover. Three experiments have been performed, 1) short term starvation, 2) addition of soy proteins to the diet, 3) use of plant protein as replacement of fish meal in the diet. For each experiment we have identified proteins that change in abundance and have used two programs, Mascot and MS-fit to identify proteins following trypsin digest fingerprinting.