To measure a spiny lobster, you measure the carapace length: the distance along the midline of the back from the rear edge of the eye socket (or the ridge between the two largest horns above the eyes) to the rear edge of the body shell. This single measurement determines whether your lobster is legal to keep. The minimum size varies by state, but the technique is the same everywhere.
Where to Place the Gauge
The carapace is the hard shell covering the lobster’s head and body, not including the tail. You’re measuring the length of this shell only, in a straight line down the center of the back. The starting point is the rear edge of the eye socket, which sits just behind and between the two large forward-pointing horns (antennae spines) on the lobster’s head. The ending point is the very back edge of the carapace, where the shell meets the first segment of the tail.
Place your gauge or measuring device so it touches the rear wall of the eye socket, then run it straight back along the midline to the rear shell edge. Keep it parallel to the center of the lobster’s back. Don’t angle the gauge to one side or follow the curve of the shell. The measurement should be a straight line, not a surface measurement that traces the shell’s contour. Even a slight curve adds length and could make an undersized lobster appear legal.
What You Need to Measure
A simple lobster gauge is the easiest tool. These are flat, rigid devices (usually plastic or metal) with a notch cut to the minimum legal size for your area. You slide the gauge over the carapace. If the shell fits entirely within the notch, the lobster is too small. If the shell extends past the gauge, it’s legal size. Gauges are inexpensive, compact, and designed for quick decisions in the water or on a boat.
A pair of calipers or a rigid ruler also works, but a gauge is faster and removes guesswork. In California, failing to carry a lobster measuring device while fishing is itself a violation, separate from any size limit issue. Many other states have similar requirements, so keep your gauge on you at all times during a dive or trap pull.
Minimum Size by Region
The legal minimum carapace length depends on where you’re fishing:
- Florida: 3 inches carapace length. If the tail has been separated from the body, the tail must measure at least 5.5 inches (not including any protruding muscle tissue).
- California: 3.25 inches (3ΒΌ inches) carapace length.
- Hawaii: Carapace length is measured from the ridge between the two largest spines above the eyes to the rear edge of the carapace. Check current Hawaii regulations for the specific minimum.
These differences matter. A lobster that’s legal in Florida could be undersized in California. Always know the rules for the specific waters you’re fishing.
When and Where to Measure
Measure before you put the lobster in your bag or cooler. Ideally, you should gauge the lobster as soon as you pull it from its hole or trap, while you can still release it quickly if it’s undersized. For divers, this means carrying your gauge on every dive and checking each lobster underwater or immediately at the surface. For trap fishers, measure at the trap before placing the lobster in your hold.
In many jurisdictions, lobsters must be landed live and whole. You cannot remove the tail or break apart the lobster before reaching shore, because officials need to verify the carapace measurement. Possessing lobster parts instead of whole animals is a separate violation in most states.
Handling the Lobster Safely
Spiny lobsters have no claws, but their shells are covered in sharp spines and points that will puncture bare skin easily. The two large horns above the eyes are especially dangerous and can poke through even some protective gloves. Wear gloves every time you handle a lobster.
Thick neoprene dive gloves offer decent protection for most of the body spines. Kevlar gloves provide better puncture resistance across most of the shell, though experienced divers note the large horn spines can still penetrate kevlar. Rubberized work gloves with textured grips (like the Atlas/Showa 660 style) are a popular, affordable choice that balances dexterity with protection. Cotton dot gloves work in a pinch but offer less defense against the sharper points.
When measuring, grip the lobster firmly by the carapace from above, keeping your fingers away from the horns. Hold it steady against a flat surface if possible, place your gauge along the midline, and read the result. A calm, firm grip reduces the chance of the lobster thrashing and driving a spine into your hand.
Egg-Bearing Females Are Always Off Limits
Regardless of size, you cannot harvest a female lobster carrying eggs. These “berried” females are easy to identify: they carry clusters of small, round eggs attached beneath the tail, visible as a dark or orange mass on the underside. Harvesting egg-bearing females, stripping eggs from females, or even bringing a berried female aboard your vessel is prohibited in most U.S. waters. If you catch one, release it immediately where you found it.
Penalties for Undersized Lobsters
Possessing undersized spiny lobsters is a misdemeanor in most states, and enforcement officers take it seriously. In California, a single violation carries up to six months in county jail and a fine of up to $1,000, but penalties and court assessments can push the total to around $4,500. A first-time offender with no record might negotiate a plea deal totaling around $1,100 in fines, a contribution to a conservation organization, three years of probation, and a stay-away order from the fishing area.
Larger violations escalate quickly. One California case involved a man who took 47 spiny lobsters in a single outing. He faced over 100 charges covering undersized lobsters, report card violations, failure to carry a measuring device, exceeding the daily bag limit, and taking lobsters for commercial purposes. He was sentenced to seven days in jail and assessed roughly $20,000 in fines, which ballooned to approximately $80,000 with penalties and assessments. The cost of keeping one borderline lobster is never worth it. When in doubt, measure again or let it go.