• boxplot;
  • caloric content;
  • forage fish species;
  • graphical analysis;
  • iterative reweighted least squares;
  • proximate analysis

To understand the relative dietary value of forage fish as prey in the Bering Sea and Gulf of Alaska, whole organisms of 13 species were analysed for proximate composition (protein, oil, ash and moisture content). Eulachon (Thaleichthys pacificus) were high in oil (total lipid) (16.8% to 21.4%) and low in moisture (64.6% to 70.8%). Oil in capelin (Mallotus villosus) ranged from 2.1% to 14.0%. Juveniles of walleye pollock (Theragra chalcogramma), Atka mackerel (Pleurogrammus monopterygius), Pacific herring (Clupea pallasii), and prowfish (Zaprora silenus) had low oil contents (< 1.8%) and high moisture contents (> 80.3%). Rankings of median proximate values illustrate the similarities. Surf smelt (Hypomesus pretiosus), rainbow smelt (Osmerus mordax), pricklebacks (Lumpenus spp.), Atka mackerel, Pacific sand lance (Ammodytes hexapterus) and Pacific sandfish (Trichodon trichodon) ranked high in median protein content (> 15.4%). Median ash content for all species ranged from 0.6% to 3.3%. Total wet mass caloric content (kcal g–1) was calculated for the four main species and a linear model was developed for caloric content as a function of moisture. The linear models (caloric content = b0 + b1 × moisture) were Pacific sand lance and Pacific sandfish (b0 = 7.82, b1 = – 0.09); eulachon (b0 = 7.97, b1 = – 0.08); and capelin (b0 = 9.70, b1 = – 0.11).