In the vast oceans, one would assume their inhabitants can travel far and wide and, as a result, populations of a species would mix freely. But this doesn’t appear to be the case for a vital forage fish called the sand lance.In the vast oceans, one would assume their inhabitants can travel far and wide and, as a result, populations of a species would mix freely. But this doesn’t appear to be the case for a vital forage fish called the sand lance.