Fish Meal: IMSBC Code Schedule and Carriage

Fish meal is one of the most fire-prone solid bulk cargoes in international trade. It is carried under Group B schedules of the IMSBC Code because of its documented history of self-heating, spontaneous combustion, and oxygen depletion. Fires triggered by misdeclared or inadequately treated fish meal have led to vessel losses. The cargo’s hazard is governed by three schedule variants in the Code, each tied to fat content, moisture, and antioxidant treatment status, with the applicable schedule determining whether the ship needs gas injection equipment, what temperature monitoring interval to follow, and what certificate the shipper must supply before loading begins.

What fish meal is and how it is produced

Fish meal is a dried, ground powder produced by cooking, pressing, and drying whole fish or fish processing waste. The raw material is typically small, oily pelagic species: Peruvian and Chilean anchoveta (Engraulis ringens), European herring and sprat, North Atlantic sand lance (capelin), and various trawl-bycatch species. White-fish species, including pollock, cod, hake, and similar lean species, yield a lower-fat meal with distinctly different hazard properties.

Processing follows four stages. The whole fish is cooked with steam or hot water to coagulate the proteins and rupture the fat cells. The cooked mass is then mechanically pressed: a screw press squeezes out the press liquor, a mixture of water and fish oil, from the solid press cake. The press cake is dried in rotating drum dryers or air-belt dryers to reduce moisture to 6 to 12 percent. The dried cake is ground to the final meal particle size of roughly 1 to 3 millimetres. The residual fish oil in the dried meal is what drives the self-heating hazard: oily pelagic meal retains 6 to 15 percent fat by mass, while fully defatted white-fish meal drops to 1 to 5 percent.

Two processing variants exist. Direct meal (also called flame-dried or full-fat meal) skips the solvent defatting step and retains all the oil that the mechanical press leaves behind. Defatted meal uses hexane extraction after pressing to strip additional oil, yielding a leaner product used in high-end aquaculture diets. Direct meal constitutes the bulk of seaborne trade and is the form most frequently shipped from Peruvian and Chilean ports.

The global trade

Peruvian anchovy meal dominates world trade. Peru accounts for roughly 30 to 35 percent of global fish meal production in years with a normal El Niño cycle, loading from the ports of Callao, Chimbote, Paita, and Pisco. Chile is the second-largest South American exporter. Norway and Iceland supply Atlantic herring and capelin meal primarily to European compound-feed mills. The United States exports Pacific Northwest pollock-based white-fish meal.

The dominant import market is China, which absorbs more than 60 percent of global fish meal trade for its aquaculture sector: shrimp, salmon, sea bass, and other intensively farmed species require high-protein, high-digestibility feed ingredients that fish meal provides at levels no plant-based protein currently matches. Vietnam, Japan, South Korea, and Taiwan are secondary Asian importers. Total global seaborne fish meal trade runs approximately 4 to 5 million tonnes per year.

Vessel sizes are predominantly Handysize bulk carriers in the 25,000 to 40,000 DWT range. South American origin ports generally have draft constraints that limit the viability of larger Supramax vessels. Stowage factor for fish meal is approximately 1.60 to 1.90 m³/t depending on moisture and particle size.

IMSBC Code schedule structure for fish meal

The IMSBC Code, adopted by IMO Resolution MSC.268(85) and in mandatory force since 1 January 2011, addresses fish meal under several distinct schedules that have evolved substantially through successive amendments. Understanding which schedule applies requires knowing the cargo’s fat content, moisture content, and antioxidant treatment status. Getting this wrong is the single most common precursor to fish meal fires at sea.

The three principal schedule variants

The table reflects the schedule framework under Amendment 07-23 (mandatory from 1 January 2025) and the coming Amendment 08-25 (mandatory from 1 January 2027). The classification history of the stabilized schedule is explained in detail below.

UN 1374: Unstabilized fish meal

UN 1374 is the IMDG Code designation for fish meal (fish scrap), unstabilized: IMDG Class 4.2 (spontaneously combustible), Packing Group II. This is the highest-hazard grade, covering fish meal that has not been treated with an effective antioxidant, or that has been treated but where the antioxidant has been depleted before the cargo reaches the ship.

The IMSBC Code includes a schedule for UN 1374, classified Group B, with requirements reflecting its extreme spontaneous-combustion hazard. In practice, most major port states, classification societies, and P&I clubs refuse to accept or insure shipments of unstabilized fish meal in bulk. It may not be transported if its temperature exceeds 35°C or 5°C above ambient. The schedule requires continuous monitoring and imposes the same gas injection and ventilation closure requirements as the stabilized schedule, but with far less tolerance for temperature drift. The risk of misdeclaration is high: a shipper who ran out of antioxidant or who failed to achieve adequate antioxidant penetration may present the cargo as stabilized (Group B MHB) when it is functionally UN 1374.

Factory ships using traditional processing at sea and vessels loading from small artisanal fishmeal plants are the contexts where unstabilized meal is most likely to be encountered. Several documented ship fires have involved fish meal that was certified as stabilized but was found by post-incident analysis to have depleted antioxidant, putting it functionally in the UN 1374 category at the time of the incident.

Stabilized fish meal: the classification history

The classification of antioxidant-treated stabilized fish meal has changed three times in recent amendments, and the current applicable regime depends on when the shipment occurs.

Before Amendment 07-23 (pre-2025): Stabilized fish meal was classified UN 2216, IMDG Class 9 (miscellaneous dangerous goods), Packing Group III. This was an IMDG-driven classification. The IMSBC Code Schedule was titled “FISH MEAL (FISH SCRAP), STABILIZED UN 2216 Anti-oxidant treated,” Group B, reflecting the cargo’s documented self-heating propensity even in the stabilized form.

Amendment 07-23 (mandatory from 1 January 2025): IMO Resolution MSC.539(107) deleted the UN 2216 schedule and introduced a new schedule, “FISH MEAL (FISH SCRAP), STABILIZED Anti-oxidant treated,” without a UN number, classified as an MHB (SH) cargo under Group B. The change was framed as alignment of the IMSBC Code with IMDG Code revisions that reconsidered the Class 9 designation. Under this regime, the cargo is Materials Hazardous only in Bulk with a self-heating (SH) characteristic, and ships carrying it must hold a Document of Compliance listing Group B MHB cargoes.

Amendment 08-25 (mandatory from 1 January 2027): Lloyd’s Register Class News 02/2026 confirmed that IMO reversed course in Amendment 08-25: stabilized fish meal is reclassified back to Class 9 dangerous goods, removing it from the MHB category. Ships carrying the cargo after 1 January 2027 will need a DG Document of Compliance listing Class 9 cargoes. Voluntary application of Amendment 08-25 is available from 1 January 2026.

This oscillation between Class 9 and MHB reflects ongoing IMO working group debates about whether the cargo’s hazard profile is better addressed through the IMDG dangerous-goods framework or through IMSBC’s MHB provisions. For operators, the practical carriage requirements (antioxidant certification, moisture limits, temperature monitoring, gas injection) remain substantially the same under either classification.

Non-hazardous white-fish meal: Group C

A Group C (non-hazardous) schedule exists for fish meal derived from white lean fish species, where the fat content does not exceed 5 percent and the moisture content does not exceed 12 percent. White-fish species, including Alaskan pollock, Atlantic cod, blue whiting, and hake, have naturally low body fat, and the resulting meal carries insufficient oil to sustain the autoxidation cycle that makes oily pelagic meal hazardous.

The Group C schedule requires that the shipper certify both thresholds. Without a certificate confirming fat not more than 5 percent and moisture not more than 12 percent, the cargo cannot be shipped as Group C and must be declared under the applicable Group B schedule. No temperature monitoring, no gas injection equipment, and no IMDG documentation are required for certified Group C fish meal.

Pollock meal from North American processors and some Icelandic cod-meal products regularly qualify for the Group C schedule when freshly processed. The practical risk is that fish meal from mixed-species sources, or from processors who blend by-catch species with lean white fish, can produce meal above the 5 percent fat threshold even when marketed as white-fish meal. A certificate based on laboratory analysis of a representative sample, rather than on species identification alone, is the only defensible basis for a Group C declaration.

The self-heating and spontaneous combustion mechanism

The hazard in oily fish meal is the autoxidation of polyunsaturated fatty acids (PUFAs) in the residual fish oil. Fish oil is distinguished from most vegetable oils by its high content of long-chain omega-3 fatty acids, particularly eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6). Both fatty acids contain five and six carbon-carbon double bonds respectively. Each double bond is a reactive site for oxygen attack.

Autoxidation chemistry

The reaction proceeds through three phases. In the initiation phase, free radicals form at the double bonds when the fatty acid molecule absorbs enough activation energy from heat, trace metal catalysts (iron and copper are particularly effective), or UV light. The free radical reacts with molecular oxygen to produce a lipid peroxy radical. In the propagation phase, the peroxy radical abstracts a hydrogen atom from an adjacent fatty acid molecule, generating a lipid hydroperoxide and a new carbon-centred radical. This new radical immediately reacts with oxygen, starting another propagation cycle. The chain reaction is self-sustaining and exponentially accelerating. In the termination phase, two radicals combine to form stable non-radical products, ending the chain. But in bulk cargo, the termination phase does not dominate until the oxygen supply is partially exhausted.

The propagation phase releases heat. Because a 6 to 15 percent fat cargo contains roughly 60 to 150 grams of reactive oil per kilogram of dry meal, and because the bulk mass has very poor thermal conductivity, the heat generated accumulates locally in the cargo body. A local hot spot develops and gradually enlarges. At temperatures above roughly 55°C, the reaction rate doubles approximately every 10°C by the Arrhenius relationship: a cargo that reaches 55°C and is not cooled or inerted can reach 100°C in a matter of hours, at which point spontaneous ignition of the dry organic matrix becomes likely.

Role of moisture

Moisture interacts with the autoxidation cycle in a nuanced way. Low moisture inhibits microbiological activity but does not prevent chemical autoxidation. Moderate moisture (roughly 8 to 12 percent) supports the growth of lipolytic bacteria and moulds, which produce enzymes that hydrolyse triglycerides to free fatty acids. Free fatty acids are more susceptible to oxidation than intact triglycerides because they lack the protective glycerol backbone. Excessively high moisture (above 12 percent) can waterlog the meal and slow oxidation by displacing oxygen from the pore spaces, but it also accelerates protein decomposition and produces ammonia, which has its own toxicity issues. The IMSBC Code moisture window of 5 to 12 percent for stabilized fish meal is calibrated to keep the cargo dry enough to be chemically stable while avoiding the high-moisture zone where microbial hydrolysis accelerates.

Oxygen depletion and CO generation

The autoxidation chain consumes molecular oxygen from the hold atmosphere. In a sealed or poorly ventilated hold loaded with oily pelagic meal, the oxygen concentration in the headspace can fall from the atmospheric 20.9 percent to below 19.5 percent within days of loading, even without any gross self-heating event. Below 19.5 percent, the atmosphere is oxygen-deficient and dangerous for entry without breathing apparatus. Below roughly 16 percent, a person loses coordination and strength rapidly. Below 10 percent, unconsciousness follows within minutes.

Carbon monoxide is produced as a secondary product of the oxidation chain: incomplete combustion of fatty acid fragments, particularly at the later stages of the propagation cycle, generates CO. CO concentrations build in the hold headspace before visible smoke or measurable temperature rise, making CO monitoring the most sensitive early-warning tool. A CO reading above 50 ppm in the hold headspace is a warning indicator. A reading above 200 ppm indicates active, accelerating self-heating. Because CO is slightly lighter than air at the same temperature but becomes stratified with warm convective plumes, it can accumulate in the upper zones of the hold access trunking and the underside of the hatch cover, where a person leaning in to take a temperature reading could be exposed to a dangerous concentration without entering the hold fully.

Effect of cargo age and antioxidant depletion

Antioxidants work by acting as preferential radical-scavengers: they react with the peroxy radicals generated in the initiation and propagation phases, producing stable radical products that don’t continue the chain. Ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) and BHT (butylated hydroxytoluene, 2,6-di-tert-butyl-4-methylphenol) are the standard synthetic antioxidants used in fish meal. Tocopherols (vitamin E analogues) are the natural antioxidant alternative adopted by markets where ethoxyquin use is restricted.

As the antioxidant is consumed by reacting with radicals, its concentration falls. The rate of depletion depends on the fat content, temperature, and oxygen availability during storage and shipment. A meal treated with 400 mg/kg ethoxyquin at production and stored in good conditions may retain 100 mg/kg or more at shipment 6 months later. A meal stored in warm, open-topped shore tanks with poor antioxidant distribution may fall below 100 mg/kg within weeks. Once the antioxidant is exhausted, the autoxidation chain proceeds essentially uninhibited, and the cargo is functionally unstabilized regardless of what the shipper’s certificate says.

The 12-month maximum shipment window after antioxidant treatment, specified in 46 CFR § 148.265 and referenced in IMSBC Code guidance, reflects the practical finding that antioxidant depletion over longer storage periods returns the cargo to effective UN 1374 status. Any fish meal offered for shipment more than 12 months after its stated production/treatment date should be rejected or subjected to independent antioxidant assay.

Antioxidant requirements and certification

Production-level concentrations

At the time of production, fish meal must be treated to the following minimum concentrations, expressed on a per-kilogram-of-meal basis:

• Ethoxyquin: at least 400 mg/kg
• Butylated hydroxytoluene (BHT): at least 1,000 mg/kg
• Tocopherol-based liquid antioxidant: at least 1,000 mg/kg

These are minimum application rates, not target concentrations. The higher production-level concentration is required because a predictable fraction of the antioxidant degrades during the drying process (temperatures in the dryer can reach 80 to 100°C) and during the initial weeks of storage when the reactive fraction of the oil is most active.

Residual concentrations at consignment

By the time the cargo is presented for loading, the residual concentrations must meet lower but still binding minimums:

• Ethoxyquin or BHT: at least 100 mg/kg
• Tocopherol-based antioxidant: at least 250 mg/kg

The difference between the production concentration and the consignment concentration is the antioxidant consumed during processing and storage. A cargo that shows exactly 100 mg/kg ethoxyquin at loading has consumed 300 mg/kg since production. That is not a problem per se, but it means the remaining antioxidant reserve is thin: a warm or prolonged voyage will deplete it faster than a cool, short one.

The shipper’s certificate

For every fish meal shipment, the shipper must provide the master with a written certificate before loading. The certificate must include:

1. The total weight of the cargo to be loaded
2. The moisture content of the cargo (measured on a representative sample)
3. The fat content of the cargo (measured on a representative sample)
4. The type of antioxidant used
5. The antioxidant concentration at the time of production
6. The antioxidant concentration at the time of shipment (residual)
7. The date of production and the date of antioxidant treatment
8. The temperature of the cargo at the time of loading

This certificate must be based on representative sampling from the production batch. A single grab sample from the surface of a shore stockpile is not representative: fish meal in a large silo or shed can be 10 to 20°C warmer and more depleted at the core than at the outer surfaces. The master has a right and a duty to verify that the declared loading temperature is consistent with what he can measure at the loading spout or in the hold, and to query the certificate if there is a discrepancy.

Where the interval between production and loading exceeds 6 months, the IMSBC Code guidance recommends a fresh antioxidant assay rather than relying solely on the production-date certificate. The US regulations (46 CFR § 148.265) require that shipment occur within 12 months of treatment; beyond that window, a fresh certificate based on current analysis is required. Shippers sometimes use older production dates to avoid the cost of reanalysis, which the master cannot independently verify. The physical condition of the cargo (temperature, color, odor) and the reasonableness of the declared parameters are the master’s primary cross-checks.

Carriage requirements under the IMSBC Code

Temperature at loading

Fish meal shall not be accepted for loading if its temperature exceeds 35°C or is more than 5°C above the ambient temperature, whichever limit is higher. Both conditions must be checked. A cargo at 30°C on a day when ambient temperature is 20°C fails the second criterion (30 is more than 5°C above 20) even though it is below 35°C.

Temperature readings at loading should be taken at multiple positions from the cargo stream or from the loaded hold immediately after each pour. Hold surface temperature alone is not sufficient: the interior of a freshly loaded pile is often 5 to 15°C warmer than the surface. Some terminal operators use thermocouple probes inserted into the cargo stream at the conveyor discharge point; others insert probes into the stow at intervals during loading. Either method is more reliable than a single thermometer reading at the hatch coaming.

Cargo arriving above the limit must be rejected. A master who accepts cargo above the temperature limit, or who accepts a certificate that understates the loading temperature, loses the protection of the IMSBC Code compliance defense in any subsequent P&I or cargo liability claim.

Temperature monitoring during the voyage

The IMSBC Code requires temperature readings at eight-hourly intervals from sensors in each loaded hold. The sensor arrangement must cover multiple depths in the cargo stow to detect localized hot spots. A configuration of at least three to four sensors per hold, positioned at the upper, mid, and lower thirds of the cargo mass, is standard.

If any sensor reads above 40°C and the temperature is rising, hold ventilators must be closed. This is not a graduated response: the Code says ventilators shall be closed, not that investigation should begin. The reason is that closing ventilation at 40°C costs nothing if the reading is an aberration, but waiting until 50°C or 55°C allows the self-heating cycle to gain energy and makes it harder to control.

If any sensor reads above 55°C and continues to rise after ventilators have been closed, CO2 or inert gas must be introduced into the hold. The gas injection proceeds slowly, over a 24-hour period where possible, to displace oxygen from the hold atmosphere. Rapid flooding with CO2 at fire-suppression concentrations (10 to 15 percent by volume) is the emergency option; controlled injection at lower concentrations over a longer period is preferable because it allows the reaction to slow without creating a hold atmosphere immediately lethal to any crew member who might need to enter.

After CO2 injection, the hold must remain sealed until discharge. Under no circumstances should the hold be opened for inspection or ventilation after a CO2 injection without full SCBA and confined-space entry procedure. A hold atmosphere containing 15 to 20 percent CO2 is immediately dangerous: CO2 at 10 percent causes unconsciousness within a minute, and a person entering without SCBA would be incapacitated before they could exit.

CO monitoring

Carbon monoxide monitoring is not always specified in every version of the IMSBC Code schedule but is recommended across class society and P&I club guidance as the best early warning of self-heating in progress. CO is produced at the earliest stages of the autoxidation acceleration phase, before temperature sensors detect any anomaly in the bulk mass.

Industry guidance treats the following CO thresholds as action levels:

• Above 50 ppm in the hold headspace: increased monitoring frequency, notify owner/manager
• Above 200 ppm: commence emergency procedures regardless of measured cargo temperature

CO readings should be taken from the sealed hold access trunking, not from above an open hatch. The trunking collects any warm, CO-laden gas rising from the cargo mass by convection; it is consistently more sensitive than an open-hatch surface measurement.

Personnel taking CO readings from the access trunking should stand clear of the opening, hold the sampling probe at arm’s length, and not put their head into the trunking. Even a partially closed hatch and a few minutes’ accumulation can produce CO concentrations above the IDLH (immediately dangerous to life and health, 1,200 ppm) in a localized pocket.

Ventilation

For stabilized Group B fish meal under normal conditions, no through-hold ventilation is required or recommended. Surface ventilation, moving air over the top of the cargo mass without drawing fresh air from the bottom of the hold upward, is acceptable in ambient temperatures. But once self-heating is detected (temperature above 40°C and rising), all ventilation to the affected hold must be closed.

The counter-intuitive aspect of fish meal ventilation is that through-ventilation accelerates, not controls, self-heating. A bulk cargo hold loaded with fish meal contains many tonnes of reactive oil distributed through millions of small pores and surfaces. Forcing fresh air through from bottom to top delivers molecular oxygen to the deepest, warmest, most reactive zone of the cargo mass, adding fuel to the chain reaction. This is the opposite of what happens with a diesel fire, where ventilation brings oxygen that might be restricting the combustion. In fish meal, oxygen is the fuel, not the oxidizer.

Gas injection equipment

The IMSBC Code requires that ships carrying Group B fish meal on voyages exceeding five days must be equipped with gas injection equipment capable of introducing CO2 or inert gas to each loaded cargo hold. The ship’s fixed fire CO2 system may satisfy this requirement only if its capacity and delivery arrangement allow controlled injection rather than rapid total-flooding. A system designed for fast fire suppression (releasing the entire cylinder bank in one activation) cannot provide the slow, controlled injection the Code specifies. Some owners fit supplemental CO2 cylinder banks or nitrogen generators dedicated to cargo hold injection.

Hold injection capacity should be confirmed before loading. The gas volume required to reduce the headspace oxygen content to below 5 percent varies with hold dimensions and cargo fill level. A 5,000 m³ gross hold volume with 4,000 m³ occupied by cargo leaves approximately 1,000 m³ headspace; reducing that headspace from 21 percent to 5 percent oxygen requires displacing roughly 160 m³ of air-equivalent oxygen, which translates to several hundred kilograms of CO2 depending on the delivery arrangement.

Enclosed-space entry procedures

Every fish meal hold, whether Group B stabilized or Group C non-hazardous, must be treated as a potential confined space before personnel entry. Oxygen depletion from autoxidation can lower the hold atmosphere to dangerous levels without any gross self-heating event. The IMSBC Code requires that before entry, tests must confirm that oxygen is at or near atmospheric concentration and that CO is absent or at a concentration safe for work.

A practical pre-entry protocol:

1. Open the hatch cover fully and allow natural ventilation for at least 15 minutes.
2. Lower a calibrated multi-gas detector (O2, CO, CO2) on a lanyard to sample the atmosphere at multiple depths: top of the access trunking, mid-height, and near the cargo surface.
3. If O2 reads below 19.5 percent or CO reads above the short-term exposure limit (50 ppm ceiling value per OSHA guidance), do not enter. Force-ventilate and retest.
4. Personnel entering wear personal gas monitors and carry SCBA rated for the detected atmosphere.
5. A standby person with SCBA remains at the hatch coaming throughout the entry.

This procedure applies at loading, during the voyage for sensor maintenance, and at discharge. Stevedores and terminal workers are not always aware of the confined-space status of a fish meal hold; the master has a duty to brief discharge stevedores before they enter.

Firefighting

Response sequence

A fish meal fire in a cargo hold is fought primarily by smothering, not by water. Water will not extinguish a deeply seated fire in a porous organic bulk cargo: the water absorbs heat at the surface, converts to steam, and may carry the burning material further into the hold via convection, while the interior of the cargo mass continues to react. CO2 or inert gas injection is the primary firefighting medium.

The response sequence, per IMSBC Code guidance and the supplementary guidance in SOLAS Chapter II-2, proceeds:

1. Close all hold vents and hatches immediately.
2. Stop the ship’s ventilation systems serving the affected hold.
3. Notify the owner, manager, and P&I correspondent.
4. If temperature is rising and approaching 55°C, begin CO2 injection slowly, targeting the headspace first.
5. Do not apply water to the hold unless CO2 injection has failed to control the fire and there is structural danger to the vessel.
6. Maintain fire watch with regular temperature readings at all neighboring holds.
7. Do not open the hold for cooling or inspection until temperature sensors show consistent decline and the hold has been gas-tested as safe.

The IMSBC Code cautions specifically against opening a hold that has been CO2-treated and then re-sealing it before the cargo has cooled. Re-admission of air to a hot cargo mass produces an immediate flashback: the oxygen concentration jumps from near-zero to atmospheric, and the hot reactive surface reignites almost instantly. Temperature must be confirmed below 40°C before any hatch cover is lifted.

Firefighting agents

CO2 is the primary agent for hold fires on bulk carriers. It is effective as a smothering agent, does not damage the cargo below the fire zone, and is compatible with the hold environment. Its limitations are that it requires an enclosed space to be effective (CO2 at 5 percent concentration will not sustain a fire; above 10 percent it suppresses it), and that it must be sustained: if CO2 injection ceases before the cargo has cooled below its auto-ignition temperature, the fire reignites.

Nitrogen is an alternative inert gas where ship installations permit. Its advantage over CO2 is that it does not produce the secondary hazard of a CO2-enriched atmosphere during crew access after the event; its disadvantage is that bulk nitrogen supply for shipboard use is less common than CO2 cylinders.

Dry chemical powder is not suitable for a hold fire in fish meal. It does not penetrate the bulk cargo mass, so it can only address a surface fire, not the deep-seated oxidation that is the root cause.

Water flooding of the hold as a last resort is appropriate only where the fire cannot be controlled by smothering and there is a risk of structural damage to the ship. Water flooding creates a massive disposal problem (contaminated bilgewater and fire water, potential hold flooding) and will likely destroy any remaining cargo value, but it can prevent total loss of the vessel.

The misdeclaration hazard

Misdeclaration is the dominant operational risk in fish meal carriage, not any failure of the chemical stabilization process per se. Two categories of misdeclaration recur in documented incidents.

Antioxidant under-treatment or depletion: The shipper applies antioxidant at the nominal production rate but achieves poor distribution through the meal, so some portions of the cargo mass are undertreated. Certificate analysis, taken from well-treated areas of the pile, passes the 400 mg/kg production-level threshold. The undertreated fraction self-heats, creating a hot spot that propagates through the bulk. The master, holding a certificate showing compliant antioxidant treatment, has no documentary basis to refuse the cargo, yet the cargo is functionally hazardous.

Fat content misrepresentation: A shipper producing oily pelagic meal from anchoveta declares a fat content of 8 percent when the cargo’s true fat content is 12 to 15 percent. The certificate is based on a sample from the dried-down edge of a storage pile rather than a core sample from the bulk. The declared figure is under the schedule limit; the actual cargo is 4 to 7 percentage points above it. This type of misdeclaration is harder for the master to detect, but physical indicators help: freshly ground oily pelagic meal has a strong, fishy, slightly rancid smell (oxidizing fat aldehydes) that is noticeably more intense than a properly stabilized, lower-fat meal. A cargo that smells strongly of rancid oil at loading is probably above the declared fat level.

A well-documented incident from the UK P&I Club Carefully to Carry series describes a Peruvian fish meal cargo where temperature sensors triggered at 40°C on day 3 of a 21-day Pacific voyage. Hold ventilators were closed. By day 5, one sensor read 55°C. CO2 injection was initiated. Temperature peaked at 70°C before declining over 4 days. The cargo arrived with severe discoloration and significant weight loss from thermal degradation. The post-incident analysis found that the antioxidant concentration in the affected hold’s cargo was 40 mg/kg, well below the 100 mg/kg consignment threshold, despite the pre-loading certificate showing 120 mg/kg. The sampling had been taken from a single surface location that was probably better treated than the bulk mass.

Trade lanes and port operations

South American export ports

The major fish meal export ports on the South American Pacific coast load from shore warehouses using conveyor systems and spout loaders into open holds. Callao (Peru) handles the largest volume, with purpose-built fishmeal terminals operated by the major Peruvian producers. Chimbote, Paita, and Pisco are secondary Peruvian loading ports. Chilean ports including Iquique, Arica, and Coronel also ship significant volumes.

Temperature monitoring should begin at loading, not after departure. Pre-loading thermometer readings from the conveyor stream at the spout discharge are standard at well-run terminals. Some shippers also insert thermocouples into the stockpile 24 hours before loading to confirm the internal temperature, not just the surface temperature.

Hold preparation must meet a grain-clean standard. Fish meal residue from a previous voyage will contaminate a fresh cargo, potentially introducing already-depleted antioxidant and partially oxidized oil into the new stow. The bilge system must be clear and free-draining because fish meal is sufficiently fine to enter bilge suction pipes, and the bilge system should not be tested or operated with meal residue in the system.

Transpacific and global routes

The dominant trade route is Peru/Chile to China, a voyage of approximately 35 to 45 days via the Panama Canal or roughly 50 to 60 days via Cape Horn. The duration makes temperature management during the passage important: 40+ day voyages allow sufficient time for a slowly developing hot spot to reach dangerous temperatures even in stabilized cargo.

Vessels loading Norwegian or Icelandic herring meal for European or Asian destinations carry shorter-duration cargoes with smaller total heat accumulation risk, but the Atlantic climate can mean higher ambient temperatures in the equatorial leg of a route through the Suez Canal, which accelerates oxidation if the cargo was already warm at loading.

Compatibility and hold preparation

Taint risk

Fish meal produces strong, persistent odours from the breakdown products of its protein and oil content, particularly trimethylamine and short-chain aldehydes. These odours transfer readily to food-grade cargoes in the same hold on a subsequent voyage if any residue remains. A thorough wash-down to grain-clean standard, including the bilge suction system, tank top, frames, and hatch coaming seals, is required before loading any food cargo or other taint-sensitive material after fish meal.

Adjacent cargo segregation

Fish meal must not be stowed in the same hold as, or adjacent to holds containing, strong oxidizers, flammable liquids, or acids. The IMDG segregation requirements for UN 1374 (Class 4.2) specify separation from flammable solids, flammable liquids, oxidizers, and organic peroxides. For stabilized fish meal under the MHB schedule, the IMSBC Code’s segregation provisions for Group B cargoes apply.

Adjacent holds carrying coal or other self-heating materials should be monitored independently: a thermal event in a coal hold can raise the bulkhead temperature toward the fish meal hold, accelerating autoxidation in the adjacent cargo. The reverse is also true.

Companion calculators

The companion reference calculators for fishmeal carriage are IMSBC Fishmeal for stowage factor and hold volume planning, and IMSBC Fishmeal Flaked for the flaked-meal variant, which has a slightly different bulk density. The general IMSBC Group A/B/C classifier cross-checks the schedule assignment against declared cargo parameters.

Amendment timeline summary

The amendments affecting fish meal carriage are more numerous and more consequential than for most bulk cargoes. Operators should verify the applicable amendment before accepting any fish meal shipment.

Operators using the 2025 IMSBC Code edition (incorporating Amendment 07-23) should note that ships carrying stabilized fish meal are currently required to hold a Document of Compliance for Group B MHB cargoes, and from 1 January 2027 will require DOC coverage for Class 9 dangerous goods in bulk. Ships whose DOC does not cover both categories should clarify coverage with their flag state and class before accepting fish meal from 2026 onwards.

Port state control and documentation

Port state control officers boarding a vessel carrying Group B fish meal have authority under SOLAS Chapter VII (which incorporates the IMSBC Code by reference, via SOLAS Chapter VI and Chapter VII) to verify:

• The shipper’s certificate is present and signed by a competent authority
• The declared BCSN and group are consistent with the certificate’s fat, moisture, and antioxidant values
• The loading temperature entry in the ship’s log or the terminal record is at or below the limit
• Temperature monitoring records for the voyage are being maintained
• Gas injection equipment is tested, operational, and of adequate capacity for the loaded holds
• The vessel’s Document of Compliance covers the applicable cargo category

Deficiencies in any of these areas can result in detention or a condition of class. The IMSBC Code is mandatory under SOLAS; it is not a recommendation. A vessel loading fish meal without a valid shipper’s antioxidant certificate is in breach of SOLAS Chapter VII. A vessel carrying Group B fish meal without functional gas injection equipment on a voyage of more than five days is similarly in breach. PSC officers at Chinese, European, and South American ports have issued detentions on both grounds.

Limitations

This article is based on the IMSBC Code as amended through Amendment 07-23 (2025 edition, mandatory from 1 January 2025) and on the confirmed changes under Amendment 08-25 (mandatory from 1 January 2027). It does not substitute for the current official text of the IMSBC Code, available from IMO publications or authorized distributors.

The antioxidant concentration figures cited here (100 mg/kg ethoxyquin or BHT, 250 mg/kg tocopherol at consignment; 400 mg/kg ethoxyquin, 1,000 mg/kg BHT or tocopherol at production) are drawn from 46 CFR § 148.265 and IMSBC Code guidance consistent with that regulation. The IMSBC Code text for a specific amendment cycle should be consulted directly for the precise schedule language.

The fat content thresholds (15 percent maximum for stabilized Group B; 5 percent maximum for Group C white-fish meal) and moisture thresholds (5 to 12 percent for stabilized Group B; 12 percent maximum for Group C) are as specified in the relevant IMSBC schedules. These thresholds do not override flag-state or competent-authority requirements that may be more conservative.

Temperature monitoring intervals specified here (eight-hourly for normal operations, four-hourly when sensors exceed 40°C) reflect IMSBC Code schedule language and US/UK practice. Individual class society rules or charterparty clauses may specify different intervals.

Incident descriptions used as illustrations in this article are drawn from published P&I club guidance and industry safety documentation. Specific vessel names and operators are not cited because the published sources present incidents anonymously.

See also

• IMSBC Code: the mandatory framework governing all solid bulk cargoes
• IMSBC Group B Cargoes: chemical-hazard Group B classification explained
• IMSBC Group C Cargoes: non-hazardous Group C classification
• Rapeseed Meal: IMSBC Code Schedule and Carriage: another Group B self-heating organic cargo with antioxidant parallels
• Cargo Hold Preparation Standards: hold cleaning requirements before loading
• Marine Fire Detection and Fixed Fire Fighting Systems: shipboard fire suppression relevant to hold fires
• SOLAS Chapter VII: Carriage of Dangerous Goods: SOLAS basis for IMSBC mandatory status
• Bulk Carrier: the vessel type used for fish meal shipments