Temperature dependent growth and yield of pikeperch, Sander lucioperca, in Finnish lakes

A non-linear growth model was used to evaluate the effects of temperature and age on annual length increments of pikeperch, Sander lucioperca (L.), in seven lakes in Finland. Length increments were derived by back-calculation using the Fraser-Lee method. Annual length increments increased from age 1 to age 3 and then decreased, while at the same time length increments and air temperature had positive correlation until age 12. Age- and size-structured yield per recruit models were used in two lakes to evaluate the effects of temperature and gillnet mesh size on pikeperch yield. In these two lakes maximum yield could be obtained with 60 and 70 mm (bar length) gill nets. In the second lake, as typically in Finland, 45-50 mm gill nets are the most frequently used. The use of larger mesh size gill nets would increase pikeperch yield from 685 to 1000 g per recruit based on the present mean temperature. In both lakes increase in temperatures would increase yield if mesh size is simultaneously increased. Higher pikeperch yield can be expected in the future because of climate warming.