Testing the Ability of a Temperature-Based Model to Predict the Growth of Age-0 Arctic Grayling

Abstract

We tested the ability of a temperature-based growth model for European grayling (also known as grayling) Thymallus thymallus to predict the growth rate of age-0 Arctic grayling T. arcticus in two reaches of a small Alaskan stream. We compared observed and predicted lengths at weekly intervals in both reaches during the summers of 2000 and 2001, calculating predicted lengths from information on daily mean water temperature and the length of larval fish at the start of the growing season. In one reach, the model accurately predicted growth over the course of both summers and the differences in growth between summers. In the other reach, observed length fell below predicted length at 4– 5 weeks of age in both years. We hypothesize that the model works well when prey abundance does not limit growth but fails when low prey density limits the fish's daily ration.