Six gamma-emitting isotopes, iron-59, cobalt-60, zinc-65, selenium-75, cesium-134 and mercury-203, were added in mid-summer to Lake 224 of the Experimental Lakes Area in northwestern Ontario, Canada. Isotope activities in whole bodies of slimy sculpins and in blood, gills, gut contents, kidney, liver and spleen of white suckers were determined for periods up to 247 days after isotope addition. Results demonstrate delay between contamination of a lake and transfer of contaminant to these fish species. General relationships between movement and distribution of isotopes in water and their accumulation in these fish indicate that direct accumulation from water is not a major route of uptake.