DIADROMY AND THE ASSEMBLY AND RESTORATION OF RIVERINE FISH COMMUNITIES - A DOWNSTREAM VIEW

Analysis of predominantly diadromous freshwater fish faunas suggests t hat migration through the sea is important in establishing and structu ring riverine fish communities by dispersion, especially at low elevat ions and close to the sea coast. This same process is considered profo undly important, also, for facilitating restoration of freshwater fish faunas after perturbation. This is demonstrated for a diversity of Ne w Zealand situations, including maintenance of fish faunas in streams on small islands that may frequently become dry, recent volcanism in t he central North Island, and Pleistocene glaciation on the west coast of the South Island. Similarly, diadromy has a probable role in the re storation of fish faunas following retreat of glaciers in Alaska from Pleistocene to modem times. The postglacial biogeography of freshwater fishes along boreal Atlantic and Pacific coasts of North America is r einterpreted in the context of faunas containing a high proportion of diadromous species. Although migratory fish in the Great Lakes are not strictly diadromous, their patterns of movement closely resemble diad romy, and the principles governing the restoration of migratory fish c ommunities in the Great Lakes may be similar to those that apply to re storation along oceanic coastlines where the importance of diadromy se ems obvious.