In experiments conducted at various hydroelectric-dam projects in the northwest to determine fish mortality resulting from turbine passage, the basic technique consisted of introducing test fish into the turbine intake and letting them pass through the turbine into the tailrace area. Control fish which do not travel through the turbine but are subjected to all other transportation and handling procedures, are simultaneously introduced into the tailrace area. Recovery of both test and control fish by use of fyke nets, floating scoop traps, large funnel-type nets, or other means, leads to determination of losses suffered during turbine transit.