The following report presents the results of- investigations on walleye and goldeye in the Peace-Athabasca Delta in 1975. The report is divided into four main sections that concern the following topics: (1) walleye in the Richardson Lake – Lake Athabasca system; (2) goldeye in the Lake Claire – Mamawi Lake system; (3) field observations of the completed Little Rapids weir on Riviere des Rochers; (4) assessment of field trials of the feasibility of marking fish with acrylic dye. Spawning success, movement, distribution, age structure, and several other biological characteristics of walleye and goldeye in the Peace-Athabasca Delta are discussed. The results of fisheries investigations in 1975 were generally incomplete because of the late initiation (mid-July) of the field work, and must therefore be interpreted carefully. BACKGROUND AND PERSPECTIVE The study on walleye and goldeye in the Peace-Athabasca Delta was sponsored by the Aquatic Fauna Technical Research Committee of AOSERP, in cooperation with the Peace Athabasca Delta Monitoring Group. This group is a multidisciplinary committee composed of representatives from governments of Alberta. Saskatchewan and Canada, and charged with the responsibility of monitoring the effects of remedial measures taken to restore water levels in the delta region. AOSERP funded the investigation in order to gain insight into baseline conditions with respect to walleye and goldeye in the Peace-Athabasca Delta. Walleye Investigations The primary objectives of this study were to delimit fry production in Richardson Lake during 1975 and to obtain the current age structure of the Lake Athabasca walleye population. A secondary objective was to obtain length-weight, age-length relationships and to determine sex ratios for the Lake Athabasca walleye. Studies on walleye fry numbers in the Delta region, surveys of some Saskatchewan streams along the south shore of Lake Athabasca and studies on life history and population dynamics of walleye in the delta have provided evidence that Richardson Lake is a major spawning ground for walleye arid that spawning in Richardson Lake provides most of the annual recruitment to the Lake Athabasca walleye population. Although all areas in the delta have not been surveyed, no other region in the delta has been identified as a major walleye spawning area. Much of Richardson Lake, and its outlet stream, Jackfish Creek, freeze to the bottom during winter. Walleye migrate from Lake Athabasca to the Athabasca River by Big Point Channel during March. Due to ice thickness and the lack of flowing water, walleye cannot enter Richardson Lake until flood waters from the Athabasca River flow into Richardson Lake via Jackfish Creek. These flood waters normally lift the ice in late April, or soon thereafter, and the spawning migration proceeds into Richardson Lake. It is possible that unusually low waters in the spring could cause conditions which would prevent or delay walleye from spawning in Richardson Lake. In view of the present situation, it appears that Richardson Lake is critical to the recruitment of walleye in Lake Athabasca and that the spawning success of this species could be seriously disrupted by unusually low water, during the spring. Goldeye Investigations The major objectives of this study were to determine the age structure of the goldeye population in the Claire-Mamawi Lakes system; and to estimate spawning success of goldeye in the system. A secondary objective was to collect information concerning seasonal movements of goldeye. Results from past studies indicate that goldeye migrate into waters of the Peace-Athabasca Delta in the spring to spawn and move back into the Peace River during summer and autumn. These studies suggest that the Chenal des Quatre Fourches is a major spring migration route for adult and juvenile goldeye as well as a major summer and autumn migration route for goldeye adults, juveniles and fry. Concern has arisen that water level control structures may block) this migration route. It was not possible to absolutely assess the spawning success of goldeye in 1975 because the number of spawners was unknown. In relative terms spawning in 1975 appeared to be less successful than in previous years. Little Rapids Weir On the basis of data gathered during ground and aerial inspections, several sites close to and on both sides of the weir and fishway have been identified as being suitable for setting gillnets. Nets cannot be set close to the weir or fishway due to strong turbulence. The dam constructed across the Flett bypass channel of Riviere des Rochers was also inspected. Water in this channel can flow through the rockfill dam, but fish cannot pass through this structure. Acrylic Dye Marking of Fish A total of 38 walleye were marked during September 1975, in Lake Athabasca near Fort Chipewyan. Most walleye were injected in the operculum (gill cover) and several were injected in the lower jaw. Injection was accomplished more easily in the operculum than in the lower jaw but because pigmentation in the lower jaw is lighter, the dye was more visible. During October 1975, 47 goldeye were marked above the weir at Little Rapids. They were injected at the origin of the anal fin. Between 30 and 40 northern pike and lake whitefish respectively were also marked. The most suitable injection site of a northern pike was at the base of either pelvic fin. Blue dye was easily visible anywhere on the ventral surface of lake whitefish, but was most visible at the base of the adipose fin. ASSESSMENT In depth investigations of spawning success, movement, distribution, age structure and other biological characteristics of walleye and goldeye populations in Peace-Athabasca Delta were conducted for the Aquatic Fauna Technical Research Committee of AOSERP. The study provides baseline information on walleye and goldeye populations with respect to the “before conditions” faced by the Athabasca Delta fisheries in view of the prospect of present and increased levels of oil sands development. This “before condition” is in the context of the “after condition” produced by remedial measures implemented after the Peace-Athabasca Delta Project Investigations into the effects of the Bennett Dam constructed on the Peace River in 1968. The report has been reviewed extensively by Research Secretariat of Alberta Environment and the Aquatic Fauna Research Committee and has been approved for publication. The content of this report does not necessarily reflect the views of Alberta Environment, Environment Canada or the Oil Sands Environmental Study Group. The mention of trade names for commercial products does not constitute an endorsement or recommendation for use. The Aquatic Fauna Committee acknowledges the importance of this report with respect to future fisheries studies in the Peace-Athabasca Delta. It will serve as the basis for studies into the effects of other manmade, structures in, the Athabasca River basin. Such basic investigations: are important since the Peace-Athabasca Delta is one of the most productive regions in Alberta. It is recognized by the Oil Sands Environmental Study Group that although innovative research methodology was not employed in the study, changes in methodology are difficult to accommodate during or after completion of a field project. The OSESG does acknowledge that the research objectives have been met and compliments the researchers on addressing themselves directly to the research subjects. The Aquatic Fauna Technical Research Committee of the Alberta Oil Sands Environmental Research Program accepts \"Walleye and Goldeye Investigations in the Peace-Athabasca Delta - 1975\" as an important and valid research document, and thanks the researchers for their scientific contributions.