Intra- and inter-population comparisons of size at reproduction, clutch size, and egg mass revealed differences between one stream and one lake population of ninespine stickleback (Pungitius pungitius) in Alaska. These results are compared with published data for a second lake population. Ninespine stickleback in the stream appeared to reproduce at a smaller overall average size and to produce greater numbers of smaller eggs per clutch than lake-dwelling ninespine stickleback. This pattern of life history traits is consistent with that reported for populations of the threespine stickleback (Gasterosteus aculeatus) in published studies from Alaska and Central Europe, suggesting stream environments favor a different set of life history tactics than lakes in both species. Further research is needed to test this hypothesis and to elucidate the causal mechanisms.