Transfer Studies of Ecologic and Genetic Variation in the American Smelt

s of American smelts, Osmerus mordax, from six established populations into eight new environments were made in Maine in 1957—62 to determine which characteristics of the parent populations would be altered by transfer to the new environments and which would remain unaltered. Four of the host lakes had not contained smelts previously, three had contained smelts which were removed by rotenone, and one is thought to have contained a smelt population which disappeared 4 or 5 years before the experimental transfer. In several cases the growth rates, lengths, and longevities attained by smelts changed greatly with change in their environment. The time of the spawning season for one stock of smelts remained unaltered following transfer to an environment where the previous smelt population routinely had spawned much later. In one case smelts hatched from eggs of a stream—spawning population adapted immediately to the shore—spawning habit in a host lake where tributaries are absent. The success of smelts in the various new environments appeared to depend mostly upon the intensity of interspecific competition and other biotic factors, as with most fishes.