Meat fill is the percentage of a crab’s shell volume that is actually filled with meat. It is the single most important quality variable in crab, and it is invisible from the outside of a carton.
Why it varies
Crabs grow by moulting: shedding the old shell and forming a new, larger one. Immediately after a moult the new shell is soft and the animal has not yet grown into it. Over the following months the crab feeds and the shell fills.
A crab caught shortly after moulting has a full-size shell and a partial amount of meat. A crab caught late in the cycle has a hard shell and is well filled. Both weigh what they weigh; the shell is a large part of that weight in both cases.
This is why fill is a lot property. It is determined by where in the moult cycle the catch happened, which in turn is why crab fisheries are regulated with closed periods around moulting.
What it costs you
Consider two 5–8 oz snow crab clusters of identical weight. If one is at 55 % fill and the other at 75 %, the meat you recover from the second is materially greater — from the same carton weight, at the same price per kilogram.
If your costing is built on meat yield rather than on cluster weight, fill is not a quality detail. It is the price.
Shell condition
Related but distinct:
- New shell — recently moulted. Softer shell, lower fill, more fragile in handling.
- Hard shell — later in the cycle. Better fill, more robust through transport and processing.
Ask for shell condition alongside fill. They correlate but they are separate observations.
Making it enforceable
A fill requirement only works if three things are in the contract:
The figure. A minimum percentage, not a target.
The method. How fill will be assessed — the technique, who performs it, and on what sample size drawn from where in the consignment.
The remedy. What happens if the assessed fill is below the minimum. A price adjustment mechanism is usually more practical than rejection for a frozen consignment that has already travelled.
Without the method, the figure is an aspiration. Most fill disputes are disagreements about measurement, not about the crab.
On king crab specifically
Red king crab is sometimes discussed purely in terms of live weight — “1.5 to 5 kg”. That range is real and useful for live shipments, but it describes the animal, not the product. For frozen clusters, fill, cluster grade, shell condition and leg breakage tolerance do the work. Do not let a live-weight range stand in for a frozen-product specification.