The semi-aquatic mammals study which was initiated in September 1976 saw its first field season during 1977-78. Research efforts were concentrated in the Muskeg River drainage area and the Dover-Snipe River headwaters area. Live trapping and tagging of the four study species, beaver (Castor canadensis), muskrat (Ondatra zibethicus), mink (Mustela vison), and otter (Lutra canadensis), were conducted while the study areas were intensively reconnoitered. Analysis of 488 otter scats showed a predominance of fish remains (85.5% contained fish) while 198 mink scats had mammals as the predominant food item (67.7% contained mammalian remains). Beaver selected Populus species (p <0.05) while in descending order of preference was willow (Salix: sp.), alder (Alnus sp.), and white birch (Betula papyrifera). Conifer species were only rarely utilized. Two mink were radio-tracked, one for a period of 5 days and the other for 21 days, during October-November and habitat utilization by the animals was documented. Beaver surveys (aerial) were conducted for the two study areas as well as the Syncrude area. A muskrat survey was undertaken for the Syncrude area also. Both beaver (+7.5%) and muskrat (+80.0%) populations had increased on the Syncrude site since a 1975-76 survey, probably due to the reduction of trapping and the provision of more habitat for muskrat. Efforts were made to begin riparian habitat mapping in the absence of such maps from other AOSERP projects. Contacts were made with the trapping community to foster co-operation in the return of tags and information regarding our tagged animals. Recommendations for future co-operative research needs and expansion of TF 3.1 into the Richardson Lakes area were itemized.