Water temperature is considered a key ecosystem driver in freshwater ponds and streams of PEI National Park. American eel and Eastern Brook trout have been chosen for evaluating pond and stream temperature conditions as they are a common residents in most Atlantic Canada water bodies. Eastern brook trout are intolerant of warm water conditions. Stream temperature and brook trout growth are important factors that can directly influence survival, growth and distribution. Brook trout migration, spawning, egg development, fry and juvenile rearing are all sensitive to the annual cycle of stream temperatures. American eel have been chosen for evaluating pond temperature conditions. The broad geographic range and diverse habitats of American eel suggests flexible temperature requirements where growth in eels can be attributed to warm water temperatures and high productivity. Hourly water temperature is measured with in-situ data loggers and assessed annually within freshwater streams and ponds of PEINP to determine: (1) the number of optimum growth hours for brook trout (>11oC - <18oC), (2) the number of hours brook trout are exposed to stressful temperatures (> 20oC), and (3) for eel, the number of growing degree days (gdd) ≥10oC in freshwater ponds.