Pacific gaper, southern gaper clam, horse clam • Tresus nuttallii
• Nuxalk - tsimani (Tresus spp.)
Identification
The Pacific gaper can be identified by the thick, leathery plates found at the tip of the siphon (siphonal plates). Its shell gapes at one end to allow room for the siphon, which still projects out of the shell when retracted. The shell is chalky white or yellowish, sometimes with patches of brown periostracum still attached. Its shell length is at least 1.5 times the height and usually more (click here for information on shell orientation). The siphon is often lighter in colour near the base. Maximum size is 23 cm.
Habitat & Range
The Pacific gaper is found buried to 1 m deep in sandy substrates. It inhabits the intertidal and subtidal to a depth of 50 m. Its range extends from central Alaska to northern Mexico.
Similar Species
The Pacific gaper is more elongated than the fat gaper (Tresus capax), and can be distinguished by the siphonal plates which the fat gaper lacks. Unlike the fat gaper, the Pacific gaper rarely hosts pea crabs.
Because of its large size, the Pacific gaper may also be mistaken for the Pacific geoduck (Panopea abrupta), which is even larger with shell valves that gape at all sides.
Human Uses
The Pacific gaper is harvested recreationally and commercially.
iNaturalist
https://www.inaturalist.org/taxa/117611-Tresus-nuttallii
The Pacific gaper can be identified by the thick, leathery plates found at the tip of the siphon (siphonal plates). Its shell gapes at one end to allow room for the siphon, which still projects out of the shell when retracted. The shell is chalky white or yellowish, sometimes with patches of brown periostracum still attached. Its shell length is at least 1.5 times the height and usually more (click here for information on shell orientation). The siphon is often lighter in colour near the base. Maximum size is 23 cm.
Habitat & Range
The Pacific gaper is found buried to 1 m deep in sandy substrates. It inhabits the intertidal and subtidal to a depth of 50 m. Its range extends from central Alaska to northern Mexico.
Similar Species
The Pacific gaper is more elongated than the fat gaper (Tresus capax), and can be distinguished by the siphonal plates which the fat gaper lacks. Unlike the fat gaper, the Pacific gaper rarely hosts pea crabs.
Because of its large size, the Pacific gaper may also be mistaken for the Pacific geoduck (Panopea abrupta), which is even larger with shell valves that gape at all sides.
Human Uses
The Pacific gaper is harvested recreationally and commercially.
iNaturalist
https://www.inaturalist.org/taxa/117611-Tresus-nuttallii
References
Cowles, D. (2005). Tresus capax (Gould, 1850). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 08/12/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest [revised]. Madeira Park, BC: Harbour Publishing. P. 127.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).
Cowles, D. (2005). Tresus capax (Gould, 1850). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 08/12/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest [revised]. Madeira Park, BC: Harbour Publishing. P. 127.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).