The Leaf River supports the most northerly known population of anadromous Atlantic salmon (Salmo salar) in Canada. River growth averaged 40–50 mm/yr, smolts averaged 258 mm fork length (range 190–300 mm) and 5.3 yr (range 4+ to 7+). Many males matured in fresh water and either incurred heavy mortality or became residual. Sex ratios among smolts were 5:1 in favor of females and among adults 3:1 in favor of females. Female 2-sea-winter salmon accounted for 75% of the fresh-run fish. Upstream migration peaked in August: kelts were still resident in the river 11 and 12 mo later.