Galaxias maculatus is one of the naturally most widely-distributed freshwater fishes in the world with populations in Australia, New Zealand, Argentina, the Falkland Islands, and Chile. In New Zealand, exploitation of post-larval shoals of G. maculatus (along with five other migratory species) as they return to freshwater from development at sea is popularly known as the whitebait fishery. Juvenile G. maculatus dominate New Zealand’s whitebait catch and in some areas they contribute up to 100% of it. To gain a better understanding of the impact that whitebait fishing has on populations of G. maculatus, we selected different stream types based on known fishing pressure (e.g., ‘closed-areas’ vs. fished) and paired them by stream order, catchment size, modelled land use, and distance from the coast, latitudinally along the West Coast of the South Island. Streams were sampled monthly for a year to estimate density, size-class structure, growth, and condition. Specifically, we tested four hypotheses: (1) there is no difference between stream types in G. maculatus density; (2) there is no difference between stream types in G. maculatus size-class structure; (3) there is no difference between stream types in G. maculatus growth rate; and (4) there is no difference between stream types in G. maculatus condition. We found differences between stream types in G. maculatus densities. In general, streams closed to fishing had greater G. maculatus densities than fished streams. However, streams with greater G. maculatus densities exhibited smaller size-class structures, slower growth rates, and poorer condition relative to streams with lower G. maculatus densities. These results indicate that whitebait fishing can lower the density of G. maculatus in streams during the fishing season, but that density-dependent mechanisms are potentially a major driver affecting the dynamics and structure of G. maculatus populations.