Updated project metadata. Zebrafish are a tropical species of fish that inhabit streams that can fluctuate dramatically in temperature. In response to a decrease in temperature, the heart of zebrafish alters the structure of the myocardium and the expression of genes that code for proteins involved in contraction. Since very little is known about the processes supporting these changes in zebrafish, this study evaluated how the protein landscape of the ventricle changes with both an acute and a chronic decrease in temperature from 27oC to 20oC at multiple time points. this tested the hypothesis that a decrease in temperature would elicit changes in protein abundance and phosphorylation to maintain heart function. This study identified 1108, 1851, 1137, and 2325 phosphopeptides at each time point and 2052, 1656, 635, and 1530 proteins at each time point.