An introduction on how to cook shellfish

Whether it’s steak and lobster or linguine and clams, shellfish is a popular choice at market seafood counters and restaurants.
Shellfish can be divided into two main categories–crustaceans and mollusks–and due to the vast size of this topic, this will be the first of three instalments.
I will discuss the main aspects of these two divisions without focusing on one particular type of shellfish in too much detail. This column and the next instalment will concentrate on the aspects of crustaceans while a third column will focus on mollusks.
All shellfish are invertebrate sea creatures, meaning they do not have an internal bone system like fish, which are called vertebrates. Almost all shellfish have a hard outer shell that protects their soft bodies from predators and the environments they thrive in.
Crustaceans is the grouping that represents crabs, lobsters, shrimp, crayfish, etc. I will focus on crabs and lobsters in this column while leaving the discussion on shrimp, prawns, and crayfish for the next one.
Buying shellfish live is almost always preferred but many don’t have this option at their marketplace. When live is an option, it’s usually only crabs and lobsters in the crustacean family that are available.
There are many ways to cook a live crab or lobster. The most common way is to submerse it head-first into a pot of boiling water to kill it instantly. Crabs then are boiled for about six-10 minutes depending on their size while lobsters usually are five-six minutes per pound.
Due to the labour required of picking the dispersed meat from crabs, they almost always are cooked this way rather than trying to extract raw flesh, which is more difficult.
Another option for killing lobsters is to hold it down firmly on a cutting board and plunge the tip of a chef’s knife into the head before cooking it. This should be done immediately before cooking it to ensure optimal freshness and flavour as the rule of thumb for raw crab or lobster is to cook it in the live form.
Raw crab and lobster flesh deteriorates very rapidly.
Lobsters also are very tasty if split in half and opened up, brushed with oil, lemon juice, and seasonings, and then grilled on the barbecue. When splitting in half, you can cut right through to serve as two halves or cut from the underside but not all the way through the top shell and serve as a whole split lobster.
If prepared in this manner, you will want to weigh down the tail portion as it will curl up and lose contact with the grill. Another way to avoid this is to cut the tail section completely through while leaving the body halves connected by the top shell.
With either grilling option, the large claws should be cracked beforehand as this will assist in cooking the claw meat at the same speed as the exposed body and tail flesh.
When working with or eating whole crab or lobster, the stomach in both cases is located just behind the eyes and should be removed and discarded.
With crabs, the feathery gills located on each side of the body under the shell also are discarded.
Dear Chef Dez:
I know it’s better to buy live shellfish but our grocery store only offers frozen crab legs. Are they cooked already?
For a nice crab dinner, how do I cook them and for how long?
Harold M.
Dear Harold:
Usually frozen crab legs already are cooked prior to freezing, and the easiest way of preparing them is in a steamer.
Submersing them in boiling water, which is a preferred technique for live crabs, will cause more flavour loss with frozen crab legs rather than steaming.
The amount of cooking time will depend on the size of the crab legs. Bring a couple of inches of water to a full boil in a pot while in the meantime arranging your crab legs as evenly as possible in a steamer basket.
Once the water is boiling, place the filled steamer over the water and immediately cover with a lid.
Normally the cooking process should take anywhere from six-10 minutes, but the safest way is to use an instant read thermometer. There almost always is a cracked part of the shell to allow for the thermometer to be inserted.
Find the thickest flesh to do this with, and serve when the internal temperature reaches 170 degrees F. They are best served simply with dishes of warming melted butter for dipping.
Send your food/cooking questions to or P.O. Box 2674, Abbotsford, B.C., V2T 6R4.
Chef Dez is a chef, writer, and host. Visit him at