John E. Halver

Ascorbic Acid Requirements of Coho Salmon and Rainbow Trout

Abstract Duplicate groups of small coho salmon and rainbow trout were fed a water-soluble vitamin test diet containing 0, 5, 10, 20, 40 or 100 mg of ascorbic acid per 100 g of dry diet. Both salmon and trout fed deficient diets developed acute lordosis or scoliosis with resultant high mortality. Rainbow trout appeared to exhaust ascorbic acid reserves more rapidly than coho salmon. Blood levels of ascorbate reflected diet content of vitamin C at lower levels of intake and anterior kidney tissue content increased directly with C level in diet. Wound repair was delayed or inhibited in fish on low C diets and results generally supported diet and tissue levels needed for rapid growth and absence of histopathology. A dietary need for vitamin C for both species was evident.

Multiple Metastasis of Rainbow Trout Hepatoma

Abstract A case of multiple metastasis in a hepatomatous rainbow trout, with metastases to eight different organs, is reported. All metastases were confirmed by histopathologic examination. Tumor emboli were found in branchial vessels in the apices of gill filaments. This case was one of 14 hepatomatous rainbow trout among which the incidence of metastasis was 30 percent.

Chemical and Histological Studies of Wild and Hatchery Salmon in Fresh Water

Abstract In a study of coho salmon (Oncorhynchus kisutch), the gross chemical and histological changes occurring over a 14-month period spent in fresh water were determined. The determinations were made at 3-month intervals on: 1) 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 the larvae in the wild environment. Both groups of fish were heavily parasitized 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 es...