Environmental and evolutionary processes affecting population dynamics and life-history of arctic grayling in western and Interior Alaska

Abstract

I compared the life-history and population dynamics of arctic grayling Thymallus arcticus in western and Interior Alaska. Fish in western Alaska grew rapidly to a large maximum size, adult mortality rates were low and juvenile mortality rates were high. As a result, western populations consisted mainly of larger, older fish. Fish in Interior streams grew more slowly to a smaller maximum size, adult mortality rates were higher and juvenile mortality rates lower than in western streams. As a result, Interior populations consisted mainly of smaller, younger fish. The relationship between body size and ovary mass was similar between regions, but Interior fish allocated a greater proportion of their annual energy budget to reproduction. I also used a foraging model to test the hypothesis that regional differences in drift-feeding opportunities were responsible for faster growth and larger size in arctic grayling in western Alaska and to determine the relative contribution of invertebrate drift density and physical habitat characteristics to regional differences in profitability. The model predicted that drift-feeding would be more profitable in western Alaska and that regional differences in invertebrate drift density and size composition were responsible for this difference.