Maturation of walleye by age, size and surplus energy

The probability of annual sexual maturation by male and female walleye Stizostedion vitreum was related to age, size and an index of condition, I _VF=[arcsine(visceral fat)^0·5(body mass)^−0·5]. Most males first matured at ages 2 and 3 years; size explained first maturation, but condition explained later maturation. In contrast, most females first matured at ages 4 and 5 years; maturity of females was more dependent upon condition. Maturity of females at ages 4 and 5 years was significantly correlated with average I _VF of the population ( PI _VF). The size reached by age 2 years (early growth) was correlated with the PI _VF. Growing degree-days, Secchi depth, latitude and lake morphology were not correlated with the PI _VF. Annual variations in female spawning stock size were related to the condition of the females, presumably reflecting the net acquisition of energy in the preceding growing season. Annual variations within lakes in the net acquisition of energy may exceed the variations in energy availability between lakes, dictated by lake morphology and geography. Thus, assessment of condition could be used to predict annual potential spawning stock size and egg production.