Growing degree-days (GDD, °C days) are an index of ambient thermal energy that relates directly to an ectotherm's cumulative metabolism but is rarely used to describe growth and development in fish. We applied GDD to length and maturity data from 416 populations of walleye (Sander vitreus) from Ontario and Quebec, Canada (mean annual GDD = 1200 to 2300 °C days). On average, males matured after they had experienced 6900 8C days and reached 350 mm total length (L) (n = 77 populations), and females matured after 10000 °C days and at 450 mm L (n = 70). Across 143 populations, GDD accounted for up to 96% of the variation in the length of immature walleye but also revealed a twofold difference in growth rate that was indicative of variation in food availability. When applied to data from eight populations in which walleye abundances have changed dramatically over time, GDD revealed a 1.3-fold increase in immature growth rate when abundance was low compared with when it was high. Our results both demonstrate the explanatory power of GDD with respect to fish growth and maturity and inform the development of regional management strategies for walleye.
|Original language||English (US)|
|Number of pages||11|
|Journal||Canadian Journal of Fisheries and Aquatic Sciences|
|State||Published - Aug 6 2010|