Two shockers, one powered with a 500-watt, 110-volt, 60-cycle alternating current generator, the other with a 2,500-watt, 230-volt, direct current unit, were compared in two blocked-off sections of Spring Brook, Kalamazoo County, Michigan. An indication of the efficiency of the D.C. unit in recovering marked fish from extremely turbid water was obtained in an unblocked section of Wilder Creek, Calhoun County, Michigan, where the use of the A. C. machine was impracticable. In one Spring Brook section, the fish were shocked, marked, and recovered first with the A. C. unit and then with the D. C. The procedure on the other section was similar except that D. C. was used first.