Lake Merced, formerly connected with the Pacific Ocean by a channel which was closed sometime between 1869 and 1894, is now a freshwater lake with a characteristic freshwater fauna, except for five species of definitely marine affinities….
Miller, Robert C.. 1958. "The relict fauna of Lake Merced, San Francisco." Journal of Marine Research 17, (1). https://elischolar.library.yale.edu/journal_of_marine_research/927