Before we look at the individual shellfish varieties, let’s define what ‘shellfish’ actually means.
Firstly, in a culinary sense, there are three main types of shellfish: crustaceans, mollusks, and echinoderms.
Each shellfish class is quite different, but they also share a common characteristic.
This common characteristic is that all shellfish have an exoskeleton (shell), usually located outside their body.
Shellfish are prevalent in numerous cuisines worldwide, and they offer significant nutritional value for very few calories.
On the downside, shellfish (particularly crustacean species) are among the most common food allergens (1).
Shellfish Groups
As noted, there are three main groups of shellfish, and these include:
Crustaceans: shellfish belonging to this category include crab, crayfish, lobster, prawn, and shrimp
Mollusks: the mollusc class of shellfish includes abalone, clam, conch, cuttlefish, limpet, mussel, nautilus, octopus, oyster, scallop, squid, whelk, and winkle
Echinoderms: this class of shellfish is lesser-known than crustaceans and molluscs, and it includes sea cucumber and sea urchin.
Types of Shellfish
Here is a list of the different shellfish varieties, their characteristics, and their main nutritional properties.
Abalone
Shellfish class: bivalve mollusk
How to eat: braised, grilled, soups and stews, steamed
Key nutrients: selenium, vitamin B5, vitamin K, vitamin E, phosphorus
Abalone is a large bivalve mollusk, and it has a hinged shell that can open and close on one side.
Nutritionally, abalone contains 105 calories per 100 grams, and it is a good source of protein, offering 17.1 grams per 100g.
Abalone also provides significant selenium and moderately high vitamin B5, vitamin K, vitamin E, and phosphorus content (2).
How to eat: baked, boiled, fried, grilled, soups and stews, steamed
Key nutrients: vitamin B12, selenium, phosphorus, choline, iron
Clams are another type of bivalve mollusk, and they are one of the most nutrient-rich seafood options.
They offer 195 calories, a small amount of omega-3, and 33.4 grams of protein per 227-gram cup. Most notably, clams are an incredibly rich source of vitamin B12, offering more than four times the recommended daily value target (3).
Additionally, clams are very easy to use and a versatile cooking ingredient. For some ideas, here are 12 interesting clam recipes.
For a simple definition, conch is a type of large sea snail.
In contrast, the perhaps lesser-known term is ‘gastropod mollusk,’ which covers species from sea snails to (land) slugs. Many gastropod mollusks, such as conch, have one coiled shell rather than hinged shells like abalone and other bivalve mollusks.
Interestingly, conch can significantly vary in size, and they can grow up to around 5 pounds (2.3 kilograms) in weight (4).
While sea snails like conch may not be a typical food in many Western countries, they are very popular in Asia and the Mediterranean region.
Additionally, conch has an excellent nutritional profile.
On this note, a 127-gram cup of sliced conch contains 165 calories and provides 33.4 grams of protein. This amount also offers more than the recommended daily value target for vitamin B12 and moderate to high amounts of numerous other vitamins and minerals (5).
Crab is part of the crustacean group of shellfish, and it is one of the most popular shellfish.
Generally speaking, crab is often eaten by itself, with crab legs being a popular choice in restaurants.
However, there is a wide variety of crab products, such as crab paste, canned crab meat, and many more.
Crab meat offers a lot of nutritional value, and a typical 134-gram crab leg provides 26 grams of protein for only 130 calories. Additionally, crab offers moderate to high amounts of most vitamins and minerals, offering especially high vitamin B12 and selenium content (6).
Crawfish are a small type of shellfish belonging to the crustaceans group.
Also known as ‘spiny lobster,’ crayfish looks somewhat like a mini version of a lobster, approximately one-quarter of the size (7).
However, despite their similar appearance, crawfish are shellfish with unique characteristics.
The nutritional profile of crawfish is impressive, with a cup serving (cooked) of the shellfish offering 23.4 grams of protein for 113 calories. Additionally, crawfish provide substantial levels of many vitamins and minerals, most notably selenium and vitamin B12 (8).
How to eat: deep-fried, dried, grilled, pan-fried, steamed
Key nutrients: Selenium, riboflavin, vitamin B12, phosphorus, iron
Cuttlefish belongs to the cephalopod group of mollusks, alongside octopus and squid.
In some countries, cuttlefish is a popular feature in the local cuisine. For example, it is popular in the Mediterranean region and can be found in pasta and paella dishes in Italy and Spain, respectively.
It is also popular in East Asian countries, where dried cuttlefish jerky is a popular snack option.
According to many people who have eaten both, cuttlefish is similar to squid but more flavorful.
One of the cuttlefish’s most noticeable nutritional properties is its protein density, providing high amounts of protein for very low calories.
A 3-oz (85g) raw weight cup of cuttlefish provides 13.8 grams of protein for only 67 calories. Also, this amount of cuttlefish offers more than half of the daily value for vitamin B12 and selenium and a broad range of nutrients in high amounts (9).
Limpet
Shellfish class: gastropod mollusk
How to eat: boiled, grilled, pan-fried, soups and stews, steamed
Key nutrients: protein
While not as popular as other shellfish, limpets are edible gastropod mollusks used as food in coastal regions.
It is difficult to find their complete nutritional profile, but a 106-gram container of limpets provides 18 grams of protein for 80 calories (10).
Lobster is a popular culinary dish around the world.
However, there are some common concerns with lobster, such as animal cruelty (from cooking live lobster), which is still legal in some countries. Additionally, lobster is not one of the most easily affordable foods.
That said, it offers an impressive nutritional profile for those who eat lobster. For example, a 150-gram lobster has 115 calories, 25 grams of protein, and nearly double the daily value for selenium and copper (11).
Lobster also provides moderately high amounts of a wide range of vitamins and minerals.
Mussels are another famous bivalve mollusk, part of the same group as abalone, clams, and oysters.
These shellfish are widely available pickled in a can or jar, and they are also popular fresh, although they can be harder to find.
Mussels are one of the best dietary sources of vitamin B12, and they also offer significant manganese content. A 3-ounce (85g) portion of raw mussels provides approximately 73 calories and 10 grams of protein (12).
Depending on where one lives, octopus may seem like a strange or regular food.
Octopus is popular in East Asia grilled, as octopus sushi, and in various soups and stews. Meanwhile, it can often be found in rice/pasta-based dishes in the Mediterranean.
Nutritionally, octopus is a rich source of vitamin B12, providing 17 mcg of vitamin B12 per 3-oz (85g) portion. The recommended daily value for vitamin B12 is 2.4 mcg, showing just how rich in B12 octopus is (13, 14).
This portion size of octopus has 70 calories and nearly 13 grams of protein.
Oyster
Shellfish class: bivalve mollusk
How to eat: boiled, broiled, grilled, pan-fried, soups and stews, steamed, sushi
Key nutrients: Zinc, vitamin B12, copper, selenium, iron
Oysters are one of the most nutrient-rich foods in the human diet, let alone among seafood options.
On this note, just one cup offers more than the recommended daily value for vitamin B12, copper, and zinc. A (248-gram) cup contains 126 calories and 14.2 grams of protein (15).
Like mussels, oysters can be found fresh and pickled in cans/jars. There may be some discernible taste differences between the two, but they are nutritionally very similar.
Scallops are highly valued for their culinary properties, and they tend to be more expensive than most common shellfish.
Aside from their taste properties, scallops are also an excellent source of selenium, phosphorus, and vitamin B12. A three-ounce (85g) portion contains 10.3 grams of protein and only 58 calories (16).
Scallops are bivalve mollusks that look similar to clams in appearance. However, there are some clear differences between the two.
Sea cucumber belongs to the echinoderm class of shellfish, which it shares with sea urchins.
Echinoderms only live in the ocean, characterized by “a hard, spiny covering or skin” (17).
Sea cucumber is not a typical food in Europe and North America, but it is a delicacy in many parts of Asia.
According to the NCC nutrition database, 100 grams of sea cucumber has 13 grams of protein for 56 calories. Additionally, it provides more than 600% of the daily value for vitamin B12 (18).
Sea Urchin
Shellfish class: echinoderm
How to eat: boiled, pickled, raw, steamed – most commonly eaten raw
Shrimp are arguably the most common and popular variety of shellfish.
There are many different ways to eat shrimp, and there are many shrimp-based foods, including everything from sandwiches to grilled shrimp and various soups.
Although it does not have as much omega-3 as oily fish, shrimp is one of the best shellfish options for this essential fatty acid.
Per three-ounce (85g) portion, shrimp has 71 calories, nearly 12 grams of protein, and it provides an excellent source of selenium (21).
On the downside, as the most popular crustacean shellfish, shrimp is one of the most common allergens in the human diet.
Squid is a type of cephalopod mollusk, similar to octopus and cuttlefish.
As food, squid enjoys popularity worldwide, although it is less common in many parts of Europe and North America.
Various types of squid dishes are available in Asia, and dried “jerky” squid is very popular.
Nutritionally, squid offers an excellent source of copper per three-ounce (85g) serving, providing almost double the recommended daily value. However, squid is also high in selenium, and this serving size has 78 calories and 13.2 grams of protein (22).
Similar to conch, whelk is a type of gastropod mollusk, or put more simply – a sea snail.
Whelk is highly nutritious, and a three-ounce (85g) serving provides more than 300% of the daily value for vitamin B12. This serving size has 116 calories and offers high amounts of copper and selenium and 20.2 grams of protein (23).
Whelk has a similar taste to clams, but it is not as widely available.
Overall, the best way to find it is by visiting a seafood-based market or restaurant, particularly in areas near the coast.
According to McCance and Widdowson’s Composition of Foods Integrated Dataset 2021 (CoFID), winkles have 73 calories, 15.4 grams of protein, and 230 mg of omega-3 per 100 grams (24).
Additionally, they provide more than 1000% of the daily value for vitamin B12, approximately double the daily value for copper, and significant amounts of magnesium, manganese, vitamin E, iron, and more.
Final Thoughts
As we can see from this guide, shellfish offer exceptional nutritional value.
They provide lots of nutrients for very low calories, making them very nutrient-dense.
Shellfish can be used in numerous ways, and pickled options sold in cans and jars can be very affordable.
For those that like seafood, shellfish can help enhance the diet’s nutritional content.
Michael works as a nutritionist in a community setting and holds a Master's Degree in Clinical Nutrition. He believes in providing reliable and objective nutritional information to allow informed decisions.
