Eggs usually hatch in 12-14 days at prevailing water temperatures but can hatch in 4-5 days 64° - 68°F (17.8°-20°C). At hatching, the young are 6-8 mm in length. They remain inactive, often attached to vegetation by means of adhesive glands on the head, for 6-10 days, and feed on the stored yolk. Growth is very rapid, by the end of a month they are 1¾ inches (43 mm) in length and 6 inches (152 mm) by the end of the first summer. growth in length continues rapidly for the first 1-3 years. Growth in length slows after sexual maturity is attained, but increase in weight rises. Growth is extremely variable from place to place over the extensive range depending of length of growing season, water temperature, and availability of food. many recent studies of growth and age determination by scales demonstrated that age interpretation is made very difficult as a result of local conditions, rate of growth, circuli number and presence of several types of false annuli. Opercular bones and possibly other cranial investing bones may give more reliable results. There is a decrease in growth rate northward and a corresponding increase in longevity. Females grow faster than males in the south but this trait is not as apparent in the north. However, females over the whole range live longer and achieve a greater maximum size than males. There is a corresponding northward and sexual difference in age at attainment of sexual maturity. In the south of Canada, females mature at 3-4 and males at 2-3 years of age whereas in the north it is age 6 for females and age 5 for males. Life expectancy in fast-growing southern Canadian populations can be as low as 10-12 years and in slow growing arctic populations as high as 24-26 years.
