-~ c. 192 Silver salmon experiment--1951 brood year In the fall of 1951, experiments with silver salmon eggs and fingerlings were conducted following the pattern used with the 1949 brood year chinook salmon. The silver salmon experiment was undertaken to provide additional information on the effect of dilute concentrations of the effluent water upon the fresh-water stage of one of the important commercial salmon inhabiting the Columbia River drainage. The use of silver salmon for such experiments has certain advantages over Chinook salmon, have a longer fresh-water life, for chinooks. Furthermore, for the silver salmon 184 months as compared to 6+ silver salmon have a shorter life span, normally returning to spawn and die at the end of their third year rather than the fourth as in the case of chinook salmon. The expectancy of return to the home stream is higher for silver salmon, being about one per cent. During the fall and winter of 1953-1954 five precocious males, "jacks," of each mark returned to the University of Washington ponds. Also some of this lot have been caught and currently are being caught in the sport fishery. The return of this lot as mature spawning fish is expected during the late fall months of 1954.