Peter I. Tack

Determination of glucose utilization in coho salmon [Oncorhynchus kisutch (Walbaum)]with (6-3H)- and (U-14C)-glucose

Abstract 1. 1. The rates of glucose utilization in juvenile coho salmon were estimated with (6-3H)-and (U-14C)-glucose. 2. 2. Estimates of glucose utilization averaged 0.43 and 0.35 mg/min per kg body weight with (6-3H)-and (U-14C)-glucose respectively; these values are much lower than observed in homoiothermic animals.

Age, Growth, and Fecundity of Yellow Perch, Perca flavescens, in Lake Michigan near Ludington, Michigan

Abstract Yellow perch were studied as a portion of a total environmental baseline study in 1972 before operation of a new pumped storage power plant on the eastern shore of Lake Michigan near Ludington. Of 1,546 perch taken by gill nets, age III (1969 year class) and IV fish contributed 40.1% and 27.4% of the total number, with male fish being taken much more frequently than females in all age classes during spring sampling. Comparative growth and length-weight data indicated that the perch were generally growing to larger sizes than those reported previously from the Great Lakes. Most fish older than age I were sexually mature and spawned in shallow littoral waters from mid-May to late June. Mature fish spent the summer in the littoral zone and moved to deeper water by late fall. The ratio of ovary weight to body weight was 20-25% before spawning, declined sharply, and increased again in fall. Ninety-six female fish examined for fecundity had a range of 10,654 to 157,594 eggs, and in general, because of ...

Age, Growth, Maturity, and Seasonal Food Habits of Round Whitefish, Prosopium cylindraceum, in Lake Michigan near Ludington, Michigan

Abstract Round whitefish were studied in 1972 and 1974 as a portion of a broad ecological study of a near-shore area of eastern Lake Michigan near Ludington, Michigan. Of 690 fish taken by gill nets, Age III fish were predominant in 1972 and Age IV in 1974. Male and female fish were taken in approximately equal numbers. About 50% of Age II and 90% of Age III fish were mature. Comparative growth and length-weight data indicated that the round whitefish were larger at any given age than those from previously reported populations. On a seasonal basis, benthic insect larvae and small mollusks were the organisms most frequently ingested.

A Comparison of the Palatability of Hatchery-Reared and Wild Brook Trout

Abstract Objective organoleptic tests scoring for aroma, flavor, texture, and moisture, were made for eight samples of wild brook trout (Salvelinus fontinalis) from two streams and for seven samples of hatchery-reared brook trout from two rearing stations. Samples were obtained during May, June, July, and August, were cooked separately by the same method, and identified by the judges by code number. Average scores of six judges showed all samples acceptable but values for wild fish from both streams were significantly higher than for hatchery-reared trout. The color of the flesh and the overall appearance of the wild trout were also more attractive. The possibility of improving the eating quality of hatchery trout through better nutrition was suggested.

The Embryology of the Coho Salmon, Oncorhynchus kisutch (Walbaum)

Abstract The early development of the coho salmon, Oncorhynchus kisutch, is similar to that of the chum salmon, Oncorhynchus keta, as already described in the literature. This study of the coho salmon begins at the closure of the blastopore where the work of previous investigators terminates. At the closure of the blastopore lips the primitive organ systems were established. Following yolk sac formation the divided brain, differentiated sensory organs, gill arches, pectoral fins, and the twisting of the heart were evident. Alevins hatched after 40 days of incubation at 10 ± 1 C, or after the eggs were subjected to approximately 720 Fahrenheit thermal units.