McCormick, S.D. and R.J. Naiman
Aquaculture, Vol. 43, pp. 269-278, 1984 WHOI-R-84-019
Size, age, growth rate and photoperiod (the controlling effects of the length of the day on phenomena such as reproductive cycles in mammals, migration patterns in birds, flowering in plants) were examined for their effects on the timing of maturation and the proportion of mature male and female brook trout (Salvelinus fontinalis). Photoperiod completely entrained the gonadosomatic index and the timing of functional maturation (spermiation and ovulation). High feed and delayed photoperiod conditions resulted in a greater proportion of mature individuals of each sex in their first year, with percent maturation higher for males. The results indicated that 1) given a positive growth rate, age and growth rate are less important than size in determining maturation of brook trout, and 2) the maturation response to size is sexually divergent. A conceptual model depicting the effects of environmental factors on size and the initiation of maturation is presented in this paper.