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Pacific Gaper
Tresus nuttallii
(a similar species is known as Tresus capax)
In-depth Information Regarding this Species
Alternate Common Names
Horse clam
Range
Rare in Oregon except in Netarts Bay where over half of the gapers in the bay are Pacific gapers (Emmett et al. 1991)
Substrate
Most abundant–fine sand or firm mud (Emmett et al. 1991)
Also in–sand, silty sand, sand/gravel, gravel (Swan and Finncan 1951, Bourne and Smith 1972, Cheney and Mumford 1986, and Wolotira et al. 1989 all in Emmett et al. 1991)
Behavior
Burrow to 25–50 cm (Cheney and Mumford 1986, Wolotira et al. 1989 both in Emmett et al. 1991)
Burrow deeper in mud or sand versus clay (Oceanographic Institute of Washington 1981 in Emmett et al. 1991)
Cannot reburrow when +6 cm in size (Pholo 1964, Wendell et al. 1976 in Emmett et al. 1991)
General Temperature Range (°C)
1–21 (Bernard 1983 in Emmett et al. 1991)
General Salinity Range (ppt)
Polyhaline–euhaline (Bernard 1983 in Emmett et al. 1991)
Average Maximum Overall Length (cm)
20 (Frey 1971, Wolotira et al. 1989 in Emmett et al. 1991)
Overall Length to Age Ratio (cm/age in years)
5/1 (Haderlie and Abbott 1980, Clarke et al. 1975 both in Emmett et al. 1991)
Overall Maximum Age (years)
17 (Frey 1971, Wolotira et al. 1989 in Emmett et al. 1991)
Overall Growth Rate
0.025 cm per day when 0.4 cm long (Frey 1971, Bourne and Smith 1972, Haderlie and Abbot 1980 all in Emmett et al. 1991)
Overall Age at Maturity (years)
2 (Frey 1971, Clarke et al. 1975, Haderlie and Abbott 1980 all in Emmett et al. 1991)
Overall Length at Maturity (cm)
5.1–7 (Frey 1971, Clarke et al. 1975, Haderlie and Abbott 1980 all in Emmett et al. 1991)
Type of Reproduction
Gonochoristic, oviparous, iteroparous
Broadcast spawner (Quayle and Bourne 1972 in Emmett et al. 1991)
Time of Year of Spawning
Year-round (Emmett et al. 1991)
Habitat where Eggs are found
Pelagic, coastal (Emmett et al. 1991)
Habitat where Larvae are found
Pelagic, coastal (Emmett et al. 1991)
Days in Larval Stage
21–30 (California) (Clarke et al. 1975 in Emmett et al. 1991)
Size when Settle out of Larval Stage (cm)
0.028 (Emmett et al. 1991)
0.2 (at 10 days old)
0.5 (at 25 days old) (Clarke et al. 1975 in Emmett et al. 1991)
Habitat where Juveniles are found
Benthic infauna (Cheney and Mumford 1986, Wolotira et al. 1989 both in Emmett et al. 1991)
Bay, estuaries, protected coastline (Frey 1971, Wolotira et al. 1989 both in Emmett et al. 1991)
Habitat where Adults are found (depth in meters)
Benthic infauna (Cheney and Mumford 1986, Wolotira et al. 1989 both in Emmett et al. 1991)
Bay, estuaries, protected coastline (Frey 1971, Wolotira et al. 1989 both in Emmett et al. 1991)
Adult Food Preference
Diatoms, Flagellates, Dinoflagellates, Detritus (including eel grass particles) (Stout 1967, Haderlie and Abbott 1980 both in Emmett et al. 1991)
Food Eaten in Laboratory Setting
Survives in aquariums with open systems or with algal culture in a closed system (Anderson 2001)
Environmental Considerations
Pollution in Washington has closed over 25% of beds (Schink et al. 1983 in Emmett et al. 1991)
Commercial Fishery
Harvested with horseneck clam (Emmett et al. 1991)
Market
Meat yield is less than 30% per clam (Quayle and Bourne 1972, Ricketts et al. 1985, Wolotira et al. 1989 all in Emmett et al. 1991)
Fragile shell (Emmett et al. 1991)
Style Species is Sold
Chowder (Frey 1971 in Emmett et al. 1991)
Shelf-life in Fresh State (days at 40°F)
Short due to fragile shell (Emmett et al. 1991)
Parasites or Disease
Paralytic Shellfish Poisoning (Emmett et al. 1991)
Intermediate host for a tapeworm that infects bat rays (Haderlie and Abbott 1980)
Recent Wild Harvest Data for Oregon
Data from the Oregon Department of Fish and Wildlife
(Pounds)
( U.S. Dollars)