Growth of Juvenile Walleye Correlated with Degree-Day Accumulation in a Large Boreal Reservoir

The influence of biotic and abiotic factors on the growth of juvenile walleye (Sander vitreus) is well documented, although there is no consensus about the main driving factors. Here, we investigated the influence of temperature, water level and forage fish abundance on the growth of juvenile walleye during the three first years of life in a large boreal reservoir, Lake St-Jean, Québec, Canada. Juvenile growth of walleye was obtained by measuring the widths of the three first annuli on the sagittal otolith of 581 walleyes obtained from annual surveys. Growth of walleye during the juvenile stage was then correlated to abiotic and biotic variables occurring in Lake St-Jean from 1995 to 2005. Growth of juvenile walleye was mainly related to the annual degree-day accumulation (R-squared values were 0.62, 0.55 and 0.37 for the first, the second and the third year of life respectively). There was no correlation between the abundance of forage fish and juvenile growth except for the third year of life. Results suggest that the growth of walleye during early juvenile stage is mostly driven by abiotic factors but gradually shift to biotic factors after few years.