Growth of age group 0 yellow perch (Perca fiavescens) and walleye (Stizostedion vitreum vitreum) was studied when temperature and light conditions (photoperiod) were varied. Fish, fed formulated dry pellets, were kept for 14 weeks at 16 and 22 C in combination with 8-and 16-hour photoperiods.Growth ranged from 151 to 539% in the walleye and from 79 to 343% in the perch during the 14-week period. Best growth for both species was found at 22 C with a 16-hour photoperiod. The temperature of 22 C ñ 1 is similar to the optimal temperature for growth of both fish in natural water.Growth of young walleye appeared to be temperature-dependent, whereas that of yellow perch was more photoperiod-dependent. The influence of temperature on the walleye growth was highly significant (P < 0.01) for all photoperiods used, whereas it was not significant for yellow perch. The effects of photoperiod on growth of walleye were not significant but they were for yellow perch (P < 0.05). PIIILLIPS. A. M., JR. 1969. Nutrition, digestion. and energy utilization. Pages 391-432 in W. S. Hoar and D. J. Randall, eds. Fish physiology. Vol. I. Academic Press, New York and London. STEEL, a. G. D., ANI) J. H. TORaIE. 1960. Principles and procedures of statistics, with special reference of the biological sciences. Mcgraw-Hill Book Co., New York, Toronto and London. 481 pp.

Synopsis Whey was effective in increasing corn yields the first and second growing season after application. If, during one season more than 4 acre‐inches of whey are applied sufficient salts may accumulate to temporarily inhibit plant growth. The protein in whey is readily converted to nitrates. Whey also benefited the soil physical status.

No abstract

The yellow perch (Perca flavescens) in Lake Mendota, Dane County, Wisconsin, normally spawn over a 2‐ to 3‐week period in April to early May when the water temperature reaches 8.0 to 12.0°C. Adult fish captured and warmed from 2.5 to 9.0–13.0°C in February began spawning in the laboratory within the same 4‐day period in April as did the fish in Lake Mendota. This was true regardless of whether the perch in the laboratory were under a 13.5‐hour light (L)/10.5‐hour dark (D) or a 10.5 L/13.5 D photoperiod. The spawning season in the laboratory, however, lasted 2 weeks longer than it did in the field. Perch captured in April spawned readily (within 7 days) in tanks under a 13.5 L/10.5 D photoperiod when the temperature was raised from 5.0 to 12.0°C. Perch also spawned under photoperiods of 18 L/6 D and 6 L/18 D when warmed from 5.0 to 12.0°C, but the predictability of spawning was decreased. Keeping fish at 5.0°C slowed but did not entirely prevent the onset of spawning. In separate tests, the proportion of females that spawned within 7 days of a 5.0 to 12.0°C temperature shift increased as the spawning season progressed. It is concluded that the onset of spawning in yellow perch depends more on the intrinsic maturational state of the gonads than on specific spring‐time photoperiod‐temperature cues. Temperature may exert a major influence on maturation and seems to have a modulating influence on spawning. However, rising temperature and/or temperature thresholds per se do not determine when perch spawning begins. Photoperiod may also have a modulating influence on spawning, but one that is not as important as that of temperature.

No abstract