Effects of Temperature and Climate Change on Young-of-the-Year Atlantic Menhaden Growth in the Chesapeake Bay

Atlantic menhaden Brevoortia tyrannus is a commercially and ecologically important prey species in the western Atlantic.  In the Chesapeake Bay, its recruitment has been low since the late 1980s prompting questions about environmental effects on their productivity.  Growth is an important component of production, but causes of spatial and temporal variability in growth of young-of-the-year (YOY) Atlantic menhaden are not fully understood.  Our objectives were to quantify the effect of temperature on spatial and temporal variability in YOY Atlantic menhaden growth in the Chesapeake Bay and project effects of temperature increases due to climate change on growth. We used data on mean length and temperature for nine regions from 1962-2011.  We developed a linear model that described mean total length of menhaden in relation to cumulative growing degree-days (GDD) in Chesapeake Bay and validated the model against data that were withheld from the initial model fitting.  The temperature threshold that best described variability in growth was 14 C, which is substantially higher than the physiological threshold for growth.  GDD explained a significant amount of variation in mean length over time (within and among years) and space.  The GDD model was also able to accurately predict mean length in tributary subsystems of the Bay that were not included in the original analysis.  Increasing temperatures under climate change scenarios led to substantial increases in Atlantic menhaden growth rates.