Smelt develop scales at 20-25 mm. length. The circuli or ridges on them grow from the anterior and posterior to meet laterally. The posterior free part of the smelt scale is larger than the anterior and is used in age determinations. When scale growth ceases during winter a "scar" or "line" forms just outside the incomplete ridges around the edge of the scale. Hatching occurs in early summer. Scales generally develop 2 to 3 months later. Some scales are only clear platelets at the end of the first growing season. The "line" which forms around the margin of each scale is the only evidence of the first annual growth check. A positive correlation exists between number of ridges formed on the scales during the first year and lengths of fish within a year-class. There is no significant difference in weight of the sexes at the same length during the fishery, though females do have a faster growth rate than males, accelerating as they grow older. In the fishery and at spawning the average size of different ages declines as the season progresses. Smelt in the Miramichi generally mature at the end of their 2 year when 105-120 mm long. They are caught in the commercial fishery in quantity for the first time during the winter preceding the end of their 2 year when they usually comprise about 2/3 of the catch. Early hatching is correlated with greater growth in the 1 year and this greater size persists as smelt grow older.