First Non-native North American Marine/Estuarine Record: 1992
First Non-native West Coast Marine/Estuarine Record: 1992
The native range of Bostrichobranchus pilularis is from at least from the Gulf of St. Lawrence to the west coast of Florida and Texas (Van Name 1945). Collections at the US National Museum of Natural History include specimens from the Arctic Ocean (e.g. USNM 19974 from the Beaufort Sea), and Colombia (USNM 25097; US National Museum of Natural History 2011). This wide geographical range suggests that multiple species may be grouped under this name. This tunicate inhabits sand and mud and is usually collected by dredging (Van Name 1945).
There is only one known record of Bostrichobranchus pilularis from the West Coast, from dredge collections in April 1992, in San Dieguito Lagoon, a small estuary north of San Diego. It was not found in subsequent collections there or elsewhere (Lambert and Lambert 1998). Since this tunicate is not usually found in fouling, or with oysters, and since the San Dieguito Lagoon receives only small-boat traffic, the mechanism of introduction is not clear.