Trim letters are the shorthand of the salmon trade. They are useful, widely understood, and — on their own — not sufficient to define a product. This guide sets out what each letter actually commits the supplier to, and what it leaves for you to specify separately.
The ladder
Each step adds removals to the one before it.
Trim A removes the backbone and the belly bones. The dorsal fin, collar bone, tail piece and belly flap are all still on the fillet, and so is the pin bone row. It is the least processed fillet in the ladder.
Trim B takes Trim A and additionally removes the dorsal fin, the collar bone, the tail piece and the belly flap. The pin bones remain.
Trim C is Trim B with the pin bones removed. This is the first step in the ladder that produces a genuinely boneless fillet.
Trim D is a fully trimmed, boneless fillet with the skin left on. Beyond Trim C, it removes remaining fin tissue, residual belly fat, the white membrane and the tail tip. It is the fillet most export programmes are built on.
Trim D+ is Trim D taken further, typically with a deeper belly cut and a tighter tolerance on membrane and residual fat. It is not a universally defined standard. If you buy D+, agree the belly depth in millimetres.
Trim E is Trim D with the skin removed: skinless, boneless, fully trimmed. It is the standard input for portioning lines and for any application where skin plays no part.
What the letter does not tell you
This is the part that costs money when it is left out. A trim letter says nothing about:
- Skin. Trim D is skin-on and Trim E is skinless, but for A, B and C the skin status is open. State it.
- Belly depth. How deep the belly is cut is a continuous variable, not a step. Agree it in millimetres.
- Tail treatment. Whether the tail tip is removed, and how far back the cut goes.
- Interleaving. Whether pieces are separated by film, or frozen together.
- Colour. If colour is contractual, specify it against a recognised colour fan.
- Fat. Varies by harvest and size class. Nobody can honestly quote a fixed figure for the species.
- Rigor state. Pre-rigor and post-rigor filleting give different shapes and different gaping risk.
- Freezing history. Never frozen, single frozen or double frozen — three different products.
Two suppliers can both deliver an entirely honest Trim D and hand you visibly different fillets, because every one of those eight attributes was left open.
What a complete specification looks like
Atlantic salmon (Salmo salar), farmed Norway. Fillet, Trim D, skin on, scaled, pin bones out. Belly trimmed to 12 mm. Tail tip removed. Size band 1.8–2.7 kg. Superior grade. Never frozen. Interleaved, 10 kg lined box. Price against net weight, no glaze.
That is thirteen fields. It takes one extra line in an email and removes every argument that would otherwise happen at delivery.
Trims on trout
The same ladder is used for fjord trout, and the removals mean the same thing. What differs is the underlying fish: fillet weight distribution, flesh colour and fat behave differently. Do not order trout by writing “same specification as our salmon” — specify the trout on its own terms.
Where to go next
- Net weight and gross weight in frozen seafood — because a trim specification without a weight basis is still incomplete.
- Single frozen and double frozen — the attribute most often left out of a salmon contract.