The annual mean age of anadromous male and female whitefish (Coregonus lavaretus) age classes in the catch years 1998–2014 in the northern (north) and southern (south) Gulf of Bothnia. The mean annual age decreased over 1998–2014 (regression for males in north: mean age = 122.382 − 0.058 × year, F _1,15 = 32.23, P < 0.001, r ² = 0.661; females in north: mean age = 64.824 − 0.029 × year, F _1,15 = 11.01, P = 0.005, r ² = 0.423; males in south: mean age = 84.170 − 0.039 × year, F _1,15 = 10.22, P = 0.006, r ² = 0.405; and females in south: mean age = 80.801–0.038 × year, F _1,15 = 5.59, P = 0.032, r ² = 0.272).