In your hand you have a lobster from the market. It’s a solid, weighty creature with a slow energy that doesn’t quite match what you’ve heard about lobsters, which is to say: crazy. Are they old or young? There’s a way to know, and it’s right there in the shell, but first you’ll have to look beyond the meat, to the biology.
Lobsters aren’t simply seafood; they’re history books. They’re a living record of the ocean’s available food and temperatures. And their story begin as an infant in the open ocean, where few survive. The lobster life cycle starts in the ocean as a swimming larva that looks nothing like an armored adult.
How Lobsters Grow and Age
For weeks, these miniature swimmer float along with currents. During that time, they will also molt many times before finally descending to settle onto sea floor as bottom-dwelling post-larval lobsters. At this point, the growing stage sets in. Lobsters must reach a size where they can defends themselves against predators such as crabs and fish, because until then they is soft and vulnerable.
To compensate, juvenile lobsters molt often. A lobster can does this up to 25 times during its first couple years. This is quite tiring since it makes them soft and exposed, but it result in impressive growth. Once a lobster grows to full size, which typically occurs by the time it becomes “legal” (meaning big enough to eat) at age seven or so, their metabolism really slow way down. From then on, they’ll shed anywhere from maybe once a year as adults (or even less frequently for some older giants, perhaps every other year?).
And this is where we start to get an idea of how trophy sized lobsters become such a rarity on dinner plates: They don’t keep growing like a linear line, growth accelerates early and then crawls to a halt. That 10-inch-wide carapace lobster you’re looking at? Chances are he’s decades old. He’s lived through many a storm and endured the weight of predators chasing him.
The sexes differ, and this affects sustainability. Females grow slower than males, often by ten to fifteen percent at any given age. To preserve this, we have the V-notch rule which states fishers must cut off the tail of female fish bearing eggs prior to release. It helps keep the population sustainable. If you’ve ever seen a chart that breaks down all those stages, you’re witnessing a time line of resilience. Juveniles run to get big. Adults runs to maintain armor.
There’s also a lot of temperature involved here. Generally speaking, warmer temperatures lead to faster growth and molting, though there are some concerns regarding health and meat density. Cooler temperatures leads to slower growth, but they produce denser and sweeter meat that chefs prize. It’s a huge part of the taste equation.
What does this mean? When you eat a lobster, you’re eating the conditions of its life. Size relates to age and how often it molts (see chart above). The main point is to respect the animal’s lifespan.
The practical part of this biology is measuring properly. Don’t measure the tip-to-tail; that’s not what you are supposed to be doing. What you’re supposed to be doing is measuring the carapace (the hard outer shell) from the eye socket to the joint at which the tail starts. That way you take the guesswork out of it. There is no question about whether you have it right or wrong when it comes time for your size limit.
The reason for a size limit is that we want our lobster population to mature to breeding age prior to being harvested. We also want to protect our big breeders from over-fishing. Balance.
So at the end of the day, what’s that massive thing in your grasp? It is the product of decades of making it work. Whether it was a half pounder when it was two years old or a ten-pound monster when it was a half century old, it survived to get here. You should of seen its growth. Knowing how old it is gives you a sense of its size and flavor. You’re doing more than purchasing dinner, you’re recognizing the life history of this creature, recorded in water and calcium.
Keep that in mind the next time you hold one in your hands. From larval stage to full grown, that’s quite a journey. It adds a sense of accomplishment to the dish.