No abstract

In data poor regions, modeled river temperatures are essential for predicting potential stressors for species at risk. With limited data from the Grand, Thames and Sydenham rivers in southern Ontario, Canada, we evaluated simple mixed effect regression models to predict water temperature using air temperature from nearby weather stations. Model performance was assessed for periods relevant to the fitness of the Black Redhorse (Moxostoma duquesni): June to August, when heat events may be likely, and May, when spawning occurs. All models performed better when trained on data from these periods, as compared to using data from the entire growing season. The best model was a linear regression using 5 days of lagged air temperature (summer mean RMSE 1.5oC). The differences in prediction error at different times of year highlight the importance of considering species ecology in model interpretation. However, the improvement in model fit when using only data from the relevant time of year suggests that relatively simple models can be used effectively in a management arena when applied appropriately.

Asian carp (bighead carp, Hypophthalmichthys nobilis; grass carp, Ctenopharyngodon idella and silver carp, H. molitrix) are a group of invasive species that are predicted to cause ecological effects if they invade the Great Lakes basin. Although Asian carp age at maturity is known to be an important factor in the risk of establishing a population, there is relatively little maturity data for North America. We found that air temperature can be used to predict the age at maturity of Asian carp. Nonlinear regressions using mean annual air temperature and annual degree days to predict age at maturity explain 60% and 62% of the variation respectively. These models predict that maturation is possible in locations that were previously excluded from Asian carp spawning range based on data from the Amur River. As expected, we find faster maturation in more southern areas of North America, although there are relatively large errors predicting age at maturity in the Mississippi River population. We conclude that due to the effect of faster maturation on population growth rates, southern Great Lakes locations (e.g. Lake Erie) may be at greater risk of faster population establishment.