Influence of environmental variability on the growth of age-0 and adult Arctic grayling

We examined the influence of river discharge and temperature on growth of a dult and age-0 Arctic grayling Thymallus arcticus in the Kuparuk River (198 5-1996) and Oksrukuyik Creek (1990-1996) during the Arctic growing season ( late June to mid-August). Grayling growth was compared against six physical variables (river, nutrient level, mean summer discharge, mean summer tempe rature, consecutive days with extreme low flow, and total days with extreme high flow) using stepwise regression analysis. Fifty-six percent of the va riance in adult grayling growth rate in both rivers was associated with nut rient level and mean summer discharge. Sixty percent of the variance in age -0 grayling weight at 40 d was associated with nutrient level, mean summer discharge, mean summer temperature, and river. The correlation with dischar ge was positive for adult grayling growth but negative for age-0 grayling w eight. This study suggests that river discharge and water temperature may i nfluence long-term survival and population dynamics of grayling in Arctic t undra streams.