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A previously undescribed virus disease epizootic of hatchery rainbow trout (Salmo gairdneri) in British Columbia, Canada is presented. In the same locality, a similar virus disease was experienced among hatchery sockeye salmon (Oncorhynchus nerka). Typical symptoms included flashing, fecal casts, hemorrhagic areas at the base of fins, and petechial hemorrhages on the visceral fat and membranes in the abdominal cavity. Histopathologic changes were typified by extensive degeneration and necrosis in the hematopoietic tissues of the kidney and spleen. A virus was isolated from both species of fish on tissue culture and the viruses showed cross‐infectivity. Based upon the pathological changes in the hematopoietic tissue and the demonstration of a vital infection, a tentative descriptive name was designated Infectious Hematopoietic Necrosis. The isolated viruses were distinctly different from the infectious pancreatic necrosis or viral hemorrhagic septicemia viruses of trout, but did show similarities to the Oregon sockeye and Sacramento River chinook viruses. Positive identification awaits further tests. The significance of these observations is the reporting of a new viral disease of rainbow trout and the extension of the geographic range of sockeye salmon viruses.

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Toxicity of Wescodyne © and Betadine© to eyed eggs was not adverse]y affected by water hardness (as calcium and magnesium) or by exposure periods up to 60 min. Both iodophors were much more toxic below pH 6.0 than at pH 8.0. In general Wescodyne was slightly more toxic than Betadine. Significant egg loss occurred if freshly fertilized eggs were water-hardened in either iodophor at 100 ppm of iodine, but egg loss at 25 ppm of iodine or at 100 ppm if the eggs were disinfected 30 rain after water hardening was comparab]e to the control Also, there was no effect on the egg mortality or fry deve]opment fo]]owing sing]e or mu]tip]e exposures after eggs were water hardened. At pH 6.0 and above, Wescodyne and Betadine at 100 ppm iodine in a 15-rain dip would be safe to use on rainbow trout eggs at any stage of development after water hardening. Recommendations and precautions for hatchery use are given. Recently there has been an increased interest in using iodophors (organic iodine complexes) for disinfecting fish eggs to preventtransmission of fish pathogens on eggs. Although fish egg disinfectants have been used for many years (Gee and Sarles 1942), Mc-Fadden (1969) pointed out the limitation of acriflavine and Thimerosal (merthiolate) disinfection and showed that Betadine • was more LITERATURE CITED AMEND, D. F., aND J.P. P1ETSCH. 1972. Virucidal activity of two iodophors to salmonid viruses. J. Fish. Res. Board Can. 29(1): 61•65.

The first confirmed epizootic of infectious hematopoietic necrosis virus disease under natural conditions is reported for sockeye salmon, Oncorhynchus nerka, in Chilko Lake, British Columbia. The outbreak occurred among fish of the 1972 brood during the spring of 1973. An estimated 825.6 million eggs were deposited in the Chilko River in 1972, and the production of 31.4 million fry that migrated into the lake in 1973 was significantly lower than the 55.1 million fry expected. The egg-to-fry survival of 3.8% was the lowest ever recorded at Chilko Lake (1949–73). The estimated fry-to-smolt survival of 57.1%, however, was well within the normal range for this lake. Apparently IHN severely reduced the survival of the 1972 brood of sockeye salmon fry at Chilko Lake, and all or nearly all of the reduction occurred during the egg-to-fry stage of the life cycle.