In a study of coho sahnon (Oncorhynchus kisutch), the gross chemical and histological changes occurring over a 14-month period spent in fresh water were detemdned. The determinations were made at 3-month intervals on: t) hatchery-reared fish, 2) fish hatchery-reared for 3, 6, 9, and 12 months and then planted in a controlled stream for the remainder of the period; and 3) an indigenous group of wild fish in this stream. Wild fish showed high incidence of tissue damage from spinose hairs of the moth larva, Halisidota argentata. Hatchery fish were similarly affected with the severity and incidence of lesions varying directly with the time of exposure of tim la•wae in the wild environment. Both groups of fish were heavily pm'asitized by sporozoan organisms in the kidney and spinal cord. Kidney disease appeared in both wild and planted hatchery fish. The gross chemical composition of hatchery fish transformed rapidly after planting to that of the wild fish. Although the initial rate of fat loss is essentially constant for all hatchery groups after planting, fish that were hatchery reared for 9 to t2 months did not complete the transformation to the wild-type body composition by the time of downstream migration at 14 months. ß 1958. The role of competition in the mortal. ity of hatchery troutß Jour. Fish. Res. Bd. Can ada, 15: 27-45. NIELSON, REED S., NORMAN REIMERS, AND HARRY D. KENNEDY. 1957. A six-year study of the survival and vitality of hatchery-reared trout of catchable size in Convict Creek, California. Califß Fish and Game, 43: 5-42. PHILLIPS, ARTIIUR M., DONALD R. BROCKWAY, MAUR-ICE BRYANT, E. O. RODERS, AND JOHN M. MAX-WELl,. 1949. The nutrition of trout. N.Y.

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