Population size, growth, and production of a unionid clam, Anodonta grandis simpsoniana, in a small, deep Boreal Forest lake in central Alberta

Unionid clams were sampled quantitatively by divers searching quadrats and by dredging in Narrow Lake, central Alberta. The mean density and biomass of Anodonta grandis simpsoniana Lea (aged ≥2 years) on the area of the littoral zone available to clams (80%) were 15/m2 and 132 g/m2 (live weight), respectively. The mean length at 5 years of age was 49 mm and only increased to 69 mm by 11 years of age. Variation in length at annulus was high. Years of small growth increments (1982 and 1983) coincided with years of poor juvenile recruitment. Production/biomass ratios were highest for clams of 2 and 3 years of age, but the amount of biomass produced was greatest for clams of 5–8 years of age. The overall production/biomass ratio (live weight) was 0.25 and varied with annual differences in growth.