Field test of two energetic models for yellow perch

Field data from a population of yellow perch Perca flavescens in Saginaw Ba y, Lake Huron, were used to evaluate the ability of two energetic models to predict consumption by yellow perch. Field estimates of daily ration for a ge-1-4 fish during May through October 1987 and 1988 were compared with ind ependent predictions made by the Wisconsin energetic model and an energetic model developed by Karas and Thoresson, Predictions of daily ration using the Wisconsin model were lower than daily rations estimated from field data for all ages, primarily due to poor model-field agreement at temperatures above 22 degrees C. This caused estimates of cumulative consumption from th e Wisconsin model to be 25-50% lower than field estimates. Predictions of d aily ration by the Karas-Thoresson model agreed with field estimates over a temperature range of 10-26 degrees C for age-1-3 yellow perch but not for older fish. Despite improvement, model predictions of cumulative consumptio n were 2-35% lower than field estimates. Although these tests of predicted and estimated rations may provide insight into which model produced more ac curate results, it must be emphasized that field measures of daily ration a re also estimates and may be in error, particularly at temperatures above 2 2 degrees C where gastric evacuation rates were estimated. The Karas-Thores son modification of the Wisconsin energetic model produced better fits to f ield ration data and is recommended for model applications.