Oysters and clams are both bivalve molluscs, but they live differently and it shows on the plate. An oyster cements itself to a hard surface and never moves; a clam burrows into sand or mud with a muscular foot and feeds through siphons. Oysters are softer and brinier and are the bivalve most often eaten raw. Clams are firmer, and gram for gram they have nearly three times the protein, while oysters have more than 70 times the zinc.
Both belong to the same broad group as mussels and scallops: animals with a two-part hinged shell, gills, and a filter-feeding habit.[1] The differences start with where each one lives.
Oyster vs clam at a glance
| Oyster | Hard clam (quahog) | |
|---|---|---|
| Where it lives | On top of the bottom, attached to a firm surface or to other oysters | Buried just below the surface of sand or mud |
| How it stays put | Lower shell cemented to the surface | Digs in with a hatchet-shaped foot |
| Foot and siphons | None as an adult | A foot and two short siphons |
| Muscles that close the shell | One | Two |
| Shell | Rough, irregular, one half cupped and one flat | Thick, rounded, two matching halves with concentric ridges |
| Typical size | 3 to 5 inches | Up to 4 inches or more |
| How it is usually eaten | Raw on the half shell, or grilled, fried, or stewed | Steamed, stuffed and baked, or in chowder |
Sources for the table: Chesapeake Bay Program field guide entries for the Eastern oyster and hard clam, and Lander University's anatomy guides for both animals.[2][3][4][5]
How their bodies differ
Oysters attach. An oyster lives with its left shell cemented to a firm surface, and as an adult it stays in one place.[4][6] Oysters attach to firm bottom and to each other, which is how reefs form.[6] An adult oyster has no foot and no siphons, and it holds its shell shut with a single adductor muscle.[4] That one muscle is what a shucker cuts; our shucking guide shows where it is.
Clams burrow. A hard clam sits shallowly buried with only the tips of its short siphons showing above the sediment.[5] It pulls water in through one siphon, filters out plankton, and pushes the used water out through the other.[3] It has a blade-like muscular foot for digging and two adductor muscles of similar size, one at each end of the shell.[5]
The shells look different. A clam's two shells are nearly identical in size and shape.[5] An oyster's are not: the bottom shell is cupped and the top one is flatter, and the outside is rough and varies from white to gray to tan.[2] Hard clam shells are thick and rounded with concentric ridges, and the inside is white with dark purple patches.[3]
Both filter feed. Neither animal hunts. Both pump water across their gills and strain out plankton. For how that works in an oyster, see what oysters eat.
Taste and texture
A raw oyster is soft and wet, and it tastes of salt first, then something sweet, often with a mineral or cucumber note at the end. That is the short version of what oysters taste like, which has flavor data from all 292 profiles on this site.
NOAA Fisheries describes the hard clam as mild, sweet, and briny.[7] The bigger difference is texture: clam meat is firmer and chewier than oyster meat. Oysters also vary more from one variety to the next. Where an oyster grew changes how salty or sweet it is, which is the idea behind merroir, and it is why raw bars list oysters by name and place.
How they are eaten
Oysters are the bivalve most often served raw, opened to order on the half shell. They are also grilled, roasted, fried, and stewed; see raw vs cooked oysters.
Clams are more often cooked. NOAA's examples are baked stuffed clams and clam chowder.[7] Hard clams are sold under different names by size: littlenecks, cherrystones, and chowder clams are all the same species.[3]
Food safety advice does not separate the two. The FDA tells people at higher risk of foodborne illness to avoid raw or undercooked shellfish in general, and names raw oysters specifically. When cooking either in the shell, the shells open as they cook, and any that stay shut should be thrown out.[8] Our guide to Vibrio and raw oyster safety covers the risk in detail.
If you are trying raw oysters for the first time, mild and small varieties are the easiest start.
Nutrition: oysters vs clams
These are USDA FoodData Central figures for raw meat, per 100 grams (about 3.5 ounces).[9][10]
| Per 100 g, raw | Eastern oyster (farmed) | Clam (mixed species) |
|---|---|---|
| Calories | 59 kcal | 86 kcal |
| Protein | 5.2 g | 14.7 g |
| Fat | 1.6 g | 1.0 g |
| Carbohydrate | 5.5 g | 3.6 g |
| Sodium | 178 mg | 601 mg |
| Zinc | 37.9 mg | 0.51 mg |
| Iron | 5.8 mg | 1.6 mg |
| Vitamin B12 | 16.2 mcg | 11.3 mcg |
| Omega-3 (EPA + DHA) | 0.39 g | 0.11 g |
What stands out:
- Protein. Clams have nearly three times as much per 100 grams.
- Zinc. Oysters have more than 70 times as much. This is the single largest difference between them.
- Sodium. The USDA's raw clam figure is more than three times the oyster figure.
- Vitamin B12. Both are very high. The FDA's Daily Value is 2.4 mcg, so 100 grams of either covers it several times over.[11]
Oyster numbers move with species. The USDA's entry for raw Pacific oysters lists 81 calories, 9.5 g of protein, and 16.6 mg of zinc per 100 grams, which is more protein and less than half the zinc of the farmed Eastern entry.[12] For the full picture on oysters, including who should limit them, see are oysters good for you.
Where mussels and scallops fit
Mussels and scallops are bivalves too, and each has its own way of living. For the full comparison with mussels, see oysters vs mussels.
| How it lives | What you eat | Per 100 g raw (USDA) | |
|---|---|---|---|
| Oyster | Cemented to a hard surface | The whole animal | 59 kcal, 5.2 g protein, 37.9 mg zinc |
| Clam | Burrowed in sand or mud | The whole animal | 86 kcal, 14.7 g protein, 0.51 mg zinc |
| Blue mussel | Anchored in place by byssal threads, the "beard" | The whole animal | 86 kcal, 11.9 g protein, 1.6 mg zinc |
| Sea scallop | Unattached on the sea floor; can swim by snapping its shells | The adductor muscle | 69 kcal, 12.1 g protein, 0.91 mg zinc |
A mussel's beard is its set of byssal threads, which anchor it in place.[13] A sea scallop can propel itself through the water by using its adductor muscle to snap its shells open and shut, and that muscle is the part Americans typically eat.[14] Nutrition figures are from USDA FoodData Central.[9][10][15]
Frequently Asked Questions
Is an oyster a type of clam?
No. Both are bivalve molluscs, but they are different animals. An oyster cements itself to a hard surface, has no foot or siphons as an adult, and closes its shell with one muscle. A hard clam burrows, has a foot and two siphons, and closes its shell with two muscles.
Do oysters and clams taste the same?
No. Oysters are softer and brinier, and they vary widely by species and growing water. Clams are firmer and chewier, with a mild, sweet, briny flavor. Oysters are more often eaten raw and clams more often cooked.
Which is healthier, oysters or clams?
Both are lean and high in vitamin B12. Per 100 grams raw, USDA figures give clams 14.7 g of protein against 5.2 g for farmed Eastern oysters, while oysters have 37.9 mg of zinc against 0.51 mg for clams and less sodium. Which one suits you depends on whether you are after protein or minerals.
How can you tell an oyster shell from a clam shell?
A clam shell is thick, rounded, and smooth with concentric ridges, and its two halves match. An oyster shell is rough and irregular, and its two halves do not match: one is cupped and the other is flatter.
Do oysters and clams live in the same places?
They can share the same bays but not the same spot. Eastern oysters live in brackish and salty water, attached to firm bottom or to each other. Hard clams live buried in sand or mud in salty water, from the shoreline down to about 60 feet.
What is the difference between oysters, clams, mussels, and scallops?
All four are bivalves that filter feed. Oysters cement themselves down, clams burrow, mussels anchor themselves with byssal threads, and scallops are unattached and can swim by snapping their shells. With scallops you usually eat only the adductor muscle; with the other three you eat the whole animal.
Sources