Hook to container,
in eleven steps.

A small wooden vessel, four crew, out of Wete, Chake Chake or Mkoani. No net aboard. Handlines and troll lines only. The vessel’s registration and the skipper’s licence are checked against the Shehia Fisher Committee register when the boat lands.

Recorded today: vessel, registration, skipperPlanned: trip log from a vessel tracker

The line goes down by hand and comes up by hand. Nothing is caught that was not aimed at, and anything unwanted goes back over the side alive. There is no sorting a net on deck and no fish aggregating device drifting for months to be recovered.

Recorded today: gear typePlanned: catch position and time from a vessel tracker

The fish is spiked and bled the moment it is aboard. A stressed fish burns through its muscle glycogen, drops its pH and goes soft — the difference between Grade 1 and Grade 2 is often decided in this minute rather than anywhere downstream.

Logged: handling method

Histamine is the reason. Scombroid species generate it enzymatically once they warm, it is not destroyed by cooking or freezing, and once it is in the fish it stays there. The only control is to get the core temperature down fast, and that control starts on the boat, not at the plant.

Target: < 15 min to iceToday: by the skipper's accountPlanned: bin probe

At the landing site the fish comes out of the slurry ice to be weighed whole, graded and issued its lot number, and goes straight back into slurry until it moves to the freezer. The number is written onto the fish tag then and there, and everything that happens afterwards attaches to it.

Recorded today: whole weight, landing site, date, lot numberPlanned: length, landing time

Colour, firmness, eye clarity, gill colour, belly condition, gaping, hook damage. The grade and the reason go onto the lot — including when the reason is a downgrade. Fat and pH checks for tuna arrive with the laboratory programme.

Recorded today: grade, defectsPlanned: fat %, pH

Histamine testing on batch samples for scombroid species, and DNA confirmation for snapper, come with the laboratory programme that is part of the facility. We do not do either today, and the specification sheet says so. Until then histamine control rests on speed to ice and cold-chain discipline. Once testing runs, anything over limit takes the whole batch off the line and the rejection is written into the ledger.

Status: plannedPlanned limit: histamine < 5 mg/kg on sample

Gilled and gutted, loined, portioned or filleted to specification. Hand filleting, because a machine cannot see a bloodline. Yield per lot is on the specification sheet where we have weighed it, so a buyer can see what they are paying for.

Recorded today: cut, trim weightPlanned: yield % per lot

Frozen the day of landing and held at −30 °C, the temperature checked and written down. Blast freezing to a −40 °C core, with the controller logging the whole curve, is what the new facility is being built to do — because how fast a fish crosses the maximum ice-crystal formation zone determines how much of its cell structure survives. We will claim that curve when a controller has recorded it.

Today: −30 °C, logged by handPlanned: −40 °C core, logged curve

Vacuum packed, glazed and put into store. Today the pack carries the lot number and the species. The full carton label — Latin binomial, FAO area, gear, catch date and a chain-of-custody number — is part of the traceability system in development, and we will print it when the data behind it is real.

Today: lot number, speciesPlanned: full carton coding

Cold store at −30 °C, well below the legal −18 °C floor, with the temperature checked and written down, and the fish shipped frozen to buyers on mainland Tanzania. The new facility is specified to hold at −45 °C — the threshold at which published research says metmyoglobin browning stops entirely — and to log the voyage temperature so the trace travels with the consignment. Until it is built we do not claim either.

Today: −30 °C, mainland TanzaniaPlanned: −45 °C hold, logged voyage trace, international export