The Syngnathus leptorhynchus species is found along the Pacific coast ranging from Bahia Santa Maria, Baja California to Prince William Sound, Alaska. Due to this large range of distribution of S. leptorhynchus, scientists are debating whether there is a single species of bay pipefish or several subspecies (Wilson 2006). Genetic evidence suggests that the southern population of S. leptorhynchus has been separated from the northern populations for a significant period of time, although there is not enough evidence to conclude that the California population is a genetically distinct species from the populations found in Alaska, Washington, and Oregon (Herald 1941, Wilson 2006).

References:

Herald E.S. 1941. A systematic analysis of variation in the western American pipefish, Syngnathus californiensis. Stanford Ichthyological Bulletin, 2: 49–73.

Wilson, A. B. 2006. Genetic signature of recent glaciation on populations of a near-shore marine fish species (Syngnathus leptorhynchus). Molecular Ecology, 15: 1857–1871.