Invasion History

First Non-native North American Tidal Record: 1938
First Non-native West Coast Tidal Record: 1938
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Busycotypus canaliculatus is native to the Northwest Atlantic from Cape Cod, Massachusetts to St. Augustine, Florida (Abbott 1974; Morris 1975; Gosner 1978). It is introduced and established in San Francisco Bay, California (Carlton 1979; Cohen and Carlton 1995). Although this snail is frequently fished and exported from the East Coast, there are no reports of introductions outside San Francisco Bay, except for an egg string found in Bolinas Lagoon, California in the 1960s (Carlton 1979).

North American Invasion History:

Invasion History on the West Coast:

Busycotypus canaliculatus was first collected in San Francisco Bay, California at Berkeley in 1938, or at Alameda in 1948 - there is confusion on the date of first record, but James T. Carlton favors 1938 (Stohler 1962; Carlton 1979). It is abundant in the south and central Bay, from Belmont Slough to Candlestick Point, and from Alameda to Berkeley (Cohen and Carlton 1995). It was collected once on the Tiburon Peninsula in 1953 (Carton 1979). Adult snails have not been found outside San Francisco Bay, but one egg string was collected in the Bolinas Lagoon in the 1960s (Carlton 1979). Possible vectors include some of the smaller and later introductions of Eastern Oysters (Crassostrea virginica), aquarium releases, or with shipments from the East Coast to Italian and Asian restaurants, although this fishery was just beginning on the East Coast in the 1940s (Cohen 2012).


Busycotypus canaliculatus is a large predatory snail, with a prominent, but blunt, spire with the suture marked by a channel giving it a stepped appearance, like a pagoda. Adult shells are dextrally coiled and have 5-6 whorls, with the body whorl making up much of the shell. The aperture is large and the siphonal canal is long. The channel has a square bottom and the shoulder above the suture is marked by a strong angle and beadlike projections. The shell has fine growth lines and the periostracum is grayish to olive with a furry felt-like covering. The shell has a yellowish aperture and an oval, brown operculum. It may reach or exceed 185 mm. This is the largest snail in its introduced range, San Francisco Bay, California (Cohen 2005), and one of the largest in its native range. Its egg cases are yellowish purse-like capsules, about 25 mm in diameter, with sharp edges and laid in conspicuous strings of up to 100 cases per string, and up to nearly a meter in length. They are frequently washed up on shore. Description from: Abbott 1974; Morris 1975; Gosner 1978; Lippson and Lippson 1997; Cohen 2005; McLean, in Carlton 2007.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Gastropoda
Subclass:   Prosobranchia
Order:   Neogastropoda
Family:   Melongenidae
Genus:   Busycotypus
Species:   canaliculatus


Buccinum ampullata (P. Müller, 1766)
Busycon canaliculatum (None, None)
Fulgur canaliculata (None, None)
Murex canaliculatus (Linnaeus, 1758)
Murex granum (Linnaeus, 1758)
Volema granulata (Link, 1807)
Pyrula canaluclata (Adams, 1839)

Potentially Misidentified Species

Busycon carica
Commonly known as the Knobbed Whelk, native to the East Coast from Massachusetts to Florida. Not introduced, but sold in Asian markets (Cohen 2012). Up to 223 mm shell length.



Busycotypus canaliculatus, the Channeled Whelk, is a large predatory marine snail. Sexes are separate and females are larger than males. Females of B. canaliculatus and the related Busycon carica mature at about 100 mm, at somewhere between 3 and 13 years of age (Magalhaes 1948; Eversole et al. 2008; Harding 2011). Fertilization is internal and development is direct. Females lay long strings of egg capsules, up to 150 capsules and a meter in length. These are usually attached to stones or other hard objects, which is buried in the substrate. Capsules contain 20-100 eggs (Lippson and Lippson 1997; Cohen 2005). In a rearing experiment, eggs hatched into shelled juveniles 3.8 mm long and fed continuously.

Busycotypus canaliculatus occurs in a variety of habitats, including oyster beds, mud and sandflats, from the intertidal zone to depths of about 15 m (Verrill and Smith 1873; Magalhaes 1948). It tolerates a wide range of temperatures and salinities, but shows signs of physiological stress at low salinities and temperatures above 22°C (Polites and Mangum 1980). Its environmental tolerances may account for its lower abundance, compared to Busycon carica and B. contrarium in the southern part of its range (Magalhaes 1948).

The Channeled Whelk detects buried bivalves by smelling the exhaled water. It feeds by using its radula to rasp and its powerful foot to pry apart the valves of bivalves. It then uses its shell to wedge apart the valves of the prey. Common prey include various species of clams, mussels, and oysters. In San Francisco Bay, native and introduced clams of the genus Macoma are likely prey (Carlton 1979). Predators of B. canaliculatus include large crabs, gulls, and humans (Lippson and Lippson 1997; Cohen 2005; Magalhaes 1948).




Seabirds, humans

Trophic Status:




General HabitatUnstructured BottomNone
General HabitatOyster ReefNone
General HabitatGrass BedNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEndobenthicNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)-2Based on geographical range
Maximum Temperature (ºC)31.5Field, Magulhaes 1948
Minimum Salinity (‰)18Experimental. Polites and Mangum 1980
Maximum Salinity (‰)38Field, Pivers Island NC
Minimum Length (mm)100Approximate size of mature females (Magulhaes 1948)
Maximum Length (mm)185Cohen 2005
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Busycotypus canaliculatus is an important fisheries item on the East Coast of the United States, and is frequently eaten, especially in southern European and Asian immigrant communities on the East and West Coast. On the East Coast, it is also an important predator of bivalves. However, we have no information on its fisheries importance, or its predatory impacts, in its introduced range in San Francisco Bay, California.

Ecological Impacts

Habitat Change: An interesting ecological impact of B. canaliculatus's invasion is the provision of larger shells for the native Hairy Hermit Crab (Pagurus hirsutiusculus), permitting it to grow to larger sizes (Wicksten 1977).

Regional Impacts

NEP-VNorthern California to Mid Channel IslandsEcological ImpactHabitat Change
The shells of Busycotypus caniculatus of Ilyanassa obsoleta, larger than those of native gastropods, may be facilitating an increase in body size of the native Pagurus hirsutiusculus (Hairy Hermit Crab), whose growth may have been limited by the size of available shells (Wicksten 1977).
P090San Francisco BayEcological ImpactHabitat Change
The shells of Busycotypus caniculatus of Ilyanassa obsoleta, larger than those of native gastropods, may be facilitating an increase in body size of the native Pagurus hirsutiusculus (Hairy Hermit Crab), whose growth may have been limited by the size of available shells (Wicksten 1977).
CACaliforniaEcological ImpactHabitat Change
The shells of Busycotypus caniculatus of Ilyanassa obsoleta, larger than those of native gastropods, may be facilitating an increase in body size of the native Pagurus hirsutiusculus (Hairy Hermit Crab), whose growth may have been limited by the size of available shells (Wicksten 1977)., The shells of Busycotypus caniculatus of Ilyanassa obsoleta, larger than those of native gastropods, may be facilitating an increase in body size of the native Pagurus hirsutiusculus (Hairy Hermit Crab), whose growth may have been limited by the size of available shells (Wicksten 1977).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NA-ET3 Cape Cod to Cape Hatteras 0 Native Estab
CAR-VII Cape Hatteras to Mid-East Florida 0 Native Estab
NEP-V Northern California to Mid Channel Islands 1938 Def Estab
P090 San Francisco Bay 1938 Def Estab
P095 _CDA_P095 (Tomales-Drakes Bay) 1970 Def Failed
NA-ET2 Bay of Fundy to Cape Cod 0 Native Unk

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
27481 Carlton 1979; Cohen and Carlton 1995) 1938 1938-01-01 Berkeley, San Francisco Bay - Berkeley Marina Def 37.8552 -122.3388
27925 Stohler 1962 1950 1950-12-20 foot of Gilman St., San Francisco Def 37.7116 -122.3735
28967 Stohler 1962; Carlton 1995 1948 1948-01-01 San Francisco Bay - Bay Farm Island Def 37.7453 -122.2183
31912 Stohler 1962; Carlton 1979 1953 1953-06-14 Tiburon, San Francisco Bay Def 37.8881 -122.4803
31924 Stohler 1962; Carlton 1979 1962 1962-01-01 Oakland Estuary, San Francisco Bay Def 37.7866 -122.2654
32524 Stohler 1962; Carlton 1979 1967 1967-09-20 Alameda Island, San Francisco Bay Def 37.7676 -122.2824
32529 Stohler 1962; Carlton 1979 1960 1960-05-15 Alameda Island, San Francisco Bay Def 37.7676 -122.2824


Abbott, R. Tucker (1974) Amarican Seashells, Van Nostrand Reinhold, New York. Pp. <missing location>

Academy of Natural Sciences of Philadelphia 2002-2016a Malacology Collection Search.

Adams, C. B. (1839) Article XI. Observations on some species of the marine shells of Massachusetts, with descriptions of five new species, Boston Journal of Natural History 2(2): 262-288

California Academy of Sciences 2005-2015 Invertebrate Zoology Collection Database.

Carlton, James T. (1979) History, biogeography, and ecology of the introduced marine and estuarine invertebrates of the Pacific Coast of North America., Ph.D. dissertation, University of California, Davis. Pp. 1-904

Carlton, James T. (Ed.) (2007) <missing title>, University of California Press, Berkeley. Pp. <missing location>

Cohen, Andrew N. 2005 Exotics Guide- Non-native species of the North American Pacific Coat. San Francisco Estuary Institute, Oakland, CA,

Cohen, Andrew N. (2012) <missing title>, California Ocean Science Trust, Sacramento CA. Pp. <missing location>

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Eversole, Arnold G.; Anderson, William D.; Isely, J. Jeffery (2008) Age and growth of the Knobbed Whelk Busycon carica (Gmelin 1791) in South Carolina subtidal waters, Journal of Shellfish Research 27(2): 423-426

Gosner, Kenneth L. (1978) A field guide to the Atlantic seashore., In: (Eds.) . , Boston. Pp. <missing location>

Harding, Juliana M. (2011) Observations on the early life history and growth rates of juvenile Channel Whelks Busycotypus canaliculatus (Linnaeus, 1758), Journal of Shellfish Research 30(3): 901-903

Lippson, Alice Jane; Lippson, Robert L. (1997) <missing title>, Johns Hopkins University Press, Baltimore. Pp. <missing location>

Magalhaes, Hulda (1948) An ecological study of snails of the genus Busycon at Beaufort, North Carolina, Ecological Monographs 18(3): 377-409

McLean, James A. (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon, University of California Press, Berkeley CA. Pp. 713-1766

Morris, Percy A. (1975) A field guide to shells of the Atlantic, Houghton-Mifflin, Boston. Pp. <missing location>

Polites, Gregory; Mangum, Charlotte P. (1980) Oxygen uptake and transport in the prosobranch mollusc Busycon canaliculatum (L.) II. Influence of acclimation salinity and temperature, Biological Bulletin 158: 118-128

Rosenberg, Gary 1995-2015 Malacolog.

Ruiz, Gregory M.; Geller, Jonathan (2018) Spatial and temporal analysis of marine invasions in California, Part II: Humboldt Bay, Marina del Re, Port Hueneme, and San Francisco Bay, Smithsonian Environmental Research Center & Moss Landing Laboratories, Edgewater MD, Moss Landing CA. Pp. <missing location>

Stohler, Rudolf (1962) Busycotypus (B.) canaliculatus in San Francisco Bay, Veliger 4(4): 211-212

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database. <missing description>

Verrill, A.E.; Smith, S.I. (1873) <missing title>, 1 Report of the United States Commission of Fish and Fisheries, <missing place>. Pp. 1-757

Wicksten, Mary (1977) Shells inhabited by Pagurus hirsutiusculus (Dana) at Coyote Point Park, San Francisco Bay, California, Veliger 19(4): 445-446