Changes in proximate composition and somatic energy content for Pacific sand lance (Ammodytes hexapterus) from Kachemak Bay, Alaska relative to maturity and season

Abstract

Mean dry-weight energy values of adult Pacific sand lance (Ammodytes hexapterus) peaked in spring and early summer (20.91 kJg−1 for males, 21.08 kJg−1 for females), then declined by about 25% during late summer and fall (15.91 kJg−1 for males, 15.74 kJg−1 for females). Late summer declines in energy density paralleled gonadal development. Gender differences in energy density (males<females) were only apparent from August to October. Adult sand lance spawn in October, entering the winter with close to their minimum whole body energy content. Juvenile sand lance exhibited a relatively constant protein to lipid ratio until they reached 80 mm fork length. Thereafter, relative proportions of protein remained constant while lipid proportions increased significantly. Dry weight energy densities of juveniles increased from a minimum 16.67 kJg−1 to a maximum of 19.68 kJg−1, and (per g) are higher than adults in late summer. The seasonal food value of adult sand lance to predators varies markedly, but maximum energetic value coincides with important feeding periods for marine mammals, fish, and seabirds.