The objective of this study was to examine reproductive indices in fish collected from the Peace, Athabasca, and Slave rivers and their major tributaries. The fish species targeted for collection and analyses were burbot, northern pike, longnose sucker, and flathead chub. Biochemical and histological approaches included analysing levels of gonadal sex steroid hormones, measuring gonad morphology, and estimating fecundity. Results are organised in to reference (upstream locations and tributaries receiving no inputs from pulp mills), near-field (within 100 kilometres downstream from a pulp mill source), and far-field (over 100 kilometres downstream) groups.