. Bulletin. Natural history; Natural history. | 1 1 1 1 1 ¥ o z z /-^ X / f^-*^^ o :! ^o- .^— e J <. JUN JULY AUG SEP OCT 1962 APR MAY JUN JULY AUG SEP OCT 1963 Fig. 7.—Growth and condition (C) of yellow perch of the 1962 year-class in the control pond lota (rectangles), add-stocic pond Theta (circles), and cropped pond Zeta (dots) during the 1962 and 1963 growing seasons. trol pond, and the relationship of condi- tion to growth was generally normal and consistent, with highest condition asso- ciated with fastest growth. The next most dominant year-class through 1962
. Bulletin. Natural history; Natural history. | 1 1 1 1 1 ¥ o z z /-^ X / f^-*^^ o :! ^o- .^— e J <. JUN JULY AUG SEP OCT 1962 APR MAY JUN JULY AUG SEP OCT 1963 Fig. 7.—Growth and condition (C) of yellow perch of the 1962 year-class in the control pond lota (rectangles), add-stocic pond Theta (circles), and cropped pond Zeta (dots) during the 1962 and 1963 growing seasons. trol pond, and the relationship of condi- tion to growth was generally normal and consistent, with highest condition asso- ciated with fastest growth. The next most dominant year-class through 1962 and 1963, both by weights and numbers, was that spawned in 1962. Fig. 7 shows that both condition and growth in the cropped population were again high, but that both growth and condition in the add-stock pond quite consistently exceeded that of the control pond. The explanation lies in the comparative abundance of the age class in the two populations. Spawning success was extremely poor in pond Theta in 1962, but exceptionally heavy in the control pond Iota. In June 1962, 2,380 Age O perch were transferred from Iota to Theta. The abundance in Iota was still such that an additional 14,664 fish of this age were thinned from Iota, mostly in 1962. By time of final census in October, 1963, this 1962 brood still numbered 3,079 in Iota, as compared to 2,861 in pond Theta, and only 230 in the cropped pond Zeta. In pond Theta the lesser number of this age class grew faster and maintained better condition, even though the num- ber and total weight of older perch was much larger in this add-stock (Theta) than in the control (Iota) population. Thus, rate of growth was more depen- dent upon abundance of the year-class (intra-year-class, or size competition) than upon total standing crop, or total population pressure. This indicates a diversity of food habits by size, and that a group of one size can make fast growth in the presence of an abundance of larg- er, more slowly growing fish,
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
