Legal Metrology at Sea: Weighing Rules for Fishing Vessels

Weighing on a fishing vessel sits at the crossroads of three sets of rules: EU fisheries control law, which says what must be weighed, where and how it is recorded; legal metrology, which says what a trustworthy weighing instrument is; and national rules, which decide approval, sealing and re-verification in practice. This hub page explains how the layers fit together and links to four detailed guides. This page is general information, not legal advice: always check the rules that apply to your vessel with your national fisheries control authority.

Three layers of rules for one scale

A scale used for catch weighing is regulated by three layers at once, and each layer answers a different question.

Layer	Question it answers	Main texts	Detailed guide
1. Fisheries control	What must be weighed, when, by whom, on which kind of system, and what records exist?	Regulation (EC) 1224/2009 as amended by 2023/2842; Implementing Regulations 2026/1932 and 2025/2196; Delegated Regulation 2025/1766	EU Fisheries Control Regulation and weighing
2. Metrological conformity	Is the instrument type fit for regulated weighing, and how is that shown?	NAWI Directive 2014/31/EU; MID 2014/32/EU Annex VIII; OIML R 76 and R 51	NAWI and MID directives explained and OIML R51 vs R76
3. National practice and use	Who approves and seals, how often is it re-verified, what must the crew check?	National metrology law; WELMEC guidance	Calibration, verification and re-verification

The layers are linked. Article 5(1) of Implementing Regulation (EU) 2026/1932 requires every system used to weigh fishery products to meet EU minimum technical requirements and to be "approved, calibrated and sealed in accordance with national law". The fisheries regulation therefore sets the outcome, and national metrology law largely decides how it is achieved.

Fisheries control in brief

Since 10 January 2026, Article 60(1) of the Control Regulation requires all quantities of fishery products landed in a Member State to be weighed per species immediately after landing, by an authorised operator, on systems approved by the competent authorities, before storage, transport or sale. Five points matter most for vessel operators:

1. The operator is accountable. The authorised operator, who may be the master, is responsible for accuracy and keeps a weighing record for each landing for three years (Article 60(5)).
2. Weighing on board is an exception. It is allowed only for sorted products, under a derogation approved by the Commission, with the flag Member State authorising the vessel and ensuring the on-board systems are approved (Article 60(3)(b)).
3. On-board results are checked at landing. Under Annex IV of Regulation 2026/1932, at least 5 % of landings weighed on board are inspected yearly; if re-weighed boxes differ from their labels by more than 5 %, the whole catch is weighed in the presence of officials.
4. Estimates must match weights. Logbook estimates must be within 10 % per species of landed quantities, or 20 % for species not exceeding 100 kg (Article 14(3)).
5. Documents must be ready. Inspectors can ask for the scale's model, serial number, latest calibration certificate with expiry date and seal numbers (Article 32, Delegated Regulation (EU) 2025/1766); on-board weighing documents must be carried or digitally accessible (Article 8(4), Implementing Regulation (EU) 2025/2196).

Legal metrology in brief

Legal metrology classifies instruments by how they work. If an operator intervenes in each weighing, the scale is a non-automatic weighing instrument under the NAWI Directive 2014/31/EU and OIML R 76. If it weighs discrete loads automatically, such as a grader or checkweigher, it is an automatic catchweigher under Annex VIII of the MID 2014/32/EU and OIML R 51.

• NAWI conformity is mandatory for six regulated uses, including commercial transactions, the application of laws and regulations, and the making-up of prepackages (Articles 1(2) and 3(2)).
• MID conformity for automatic instruments is required where a Member State prescribes it (Article 3).
• Conformity is visible as CE, a boxed M with the last two digits of the year and the notified body number (NAWI Articles 16-17; MID Articles 21-22).
• Accuracy classes I, II, III and IIII (non-automatic) and XI-XIIII or Y(I)-Y(b) (automatic) set the verification scale interval, number of intervals and minimum capacity.

Where motion at sea fits in

A vessel's heave, pitch and roll add vertical acceleration to gravity and tilt the platform, so the force on a load cell changes while the mass does not; the physics are covered in why ordinary scales fail at sea on the weighing at sea hub. Legal metrology handles this through general influence requirements rather than a dedicated ship standard:

Effect	Requirement	Source
Tilt, non-automatic scales	Class II-IIII instruments liable to be tilted must be sufficiently insensitive to normal tilting	NAWI Annex I, 7.1; R 76-1, 3.9.1.1
Tilt sensor behaviour	May compensate; must blank display and inhibit printing and data transmission beyond the limit	R 76-1, 3.9.1.1(b)
Disturbed equilibrium	No printing, storing, zeroing or taring during disturbance	R 76-1, 4.4.2
Acceleration on ships	Compensation to at least ±3 m/s², dynamic test at no more than 0.3 Hz	WELMEC Guide 2:2023, 2.3.1
Tilt on ships	Tilt tests up to 25 % (15°); dynamic tilt at 0.03-0.3 Hz	WELMEC Guide 2:2023, 2.3.1
Automatic instruments	Means to limit effects of tilt, loading and rate of operation	MID Annex VIII, Ch. I, 3.1

WELMEC Guide 2:2023 is guidance for notified bodies, not law, but it is a published European reference that deals specifically with how scales installed in ships are examined. It also confirms that in-service control and periodic verification are dealt with nationally.

The EU fisheries rules add one point to watch. Annex I, point 1(b) of Regulation 2026/1932 requires weighing systems to stand on a stable and level surface, but exempts hanging scales and systems used for weighing on board under Annex IV, "provided that such scales and systems are stationary at the time of weighing and that any swinging does not affect the accuracy of the weighing results". How authorities apply that wording to motion-compensated scales should be confirmed with the flag state.

Key dates at a glance

Date	Event
20 Apr 2016	NAWI Directive 2014/31/EU and MID 2014/32/EU apply
9 Jan 2024	Regulation (EU) 2023/2842 enters into force
10 Jul 2024	New margins of tolerance in Article 14 apply
10 Jan 2026	New Article 60 weighing rules apply; Regulations 2025/2196 and 2025/1766 apply
10 Jan 2027	Old sampling plans and control plans end; weighing Articles 71-77 of Regulation 404/2011 cease
11 Jan 2027	Implementing Regulation 2026/1932 applies
10 Jan 2028	End of transitional measures in approved weighing plans
10 Jan 2030	Electronic weighing records; end of general 2 % ice and water deduction; new belt and batch system functions

Which rules apply to your situation?

Situation	Fisheries control	Metrology	Start here
EU vessel landing fresh fish at an EU auction	Weighing after landing by the auction or another authorised operator	Auction's scales approved under national law	EU weighing rules
EU vessel that wants to weigh sorted catch on board	Flag state authorisation under an approved Article 60(3)(b) derogation; Annex IV labelling and inspections	On-board scale approved, calibrated and sealed under the flag state's law	EU weighing rules, then calibration guide
Freezer vessel packing and labelling boxes by weight	Frozen product sampling plan (Annex III) if a derogation applies	NAWI for prepackages; MID if automatic labelling is prescribed nationally	NAWI and MID guide
Grading fish automatically on board or ashore	Depends on whether the grader's weight is the Article 60 weight	OIML R 51 / MID MI-006 where prescribed	OIML R51 vs R76
Research vessel weighing samples	Usually outside Article 60	Usually outside the regulated uses; traceable calibration still advisable	Calibration guide; research vessels hub

A buyer's checklist for regulated weighing at sea

1. Define the use. Write down what the weight is used for: first sale, Article 60 weighing, prepackage labelling, internal control or research.
2. Ask the authority first. Contact your fisheries control authority and, where relevant, the metrology authority, and ask which approval, verification and sealing they require for that use on your vessel.
3. Classify the instrument. Operator-driven or automatic decides NAWI and R 76 versus MID and R 51.
4. Choose class, Max and e. Check that your lightest regulated load is above Min and that the maximum permissible error suits your tolerance.
5. Check the paperwork. Ask for the EU-type examination certificate and its conditions, the declaration of conformity and the data plate layout.
6. Check marine suitability. Ask how motion, tilt and gravity changes are handled and tested, and what the temperature range is.
7. Plan records. Make sure the system can produce the weighing record fields in Article 3 of Regulation 2026/1932, and the logs Annex I requires for belt systems.
8. Plan verification and checks. Agree who verifies and seals, at what interval, and set up a daily routine check with suitable test weights.
9. Plan for failure. Article 5(3) of Regulation 2026/1932 requires switching to another approved system or stopping weighing if a fault affects accuracy.

Construction choices that keep a scale accurate over years, such as stainless steel grade, ingress protection and cleaning, are covered on the hygiene and materials hub. Integration of weighing data with catch management systems is covered on the data integration hub.

Common misconceptions

Several assumptions about weighing at sea are widespread but do not match the texts.

• "A calibrated scale is an approved scale." Calibration quantifies errors against reference weights; approval and verification are legal decisions that end with a mark, seal or certificate. Regulation 2026/1932 requires systems to be approved, calibrated and sealed, which are three separate conditions.
• "A CE mark is enough." The CE mark can relate to other EU legislation. Metrological conformity is shown by the M rectangle with the year and a notified body number next to it.
• "Weighing on board replaces weighing at landing." Under Article 60(3)(b), sorted products weighed on board are still subject to a sampling plan at landing, and the Member State of landing may require re-weighing (Annex IV, point 6).
• "Motion compensation makes any scale legal." Compensation addresses accuracy on a moving deck; it does not replace conformity assessment, national approval or verification.
• "The rules only apply from 2027." The Article 60 obligations have applied since 10 January 2026; 11 January 2027 is when the detailed Implementing Regulation 2026/1932 starts to apply.

Key terms in one sentence each

• Authorised weighing operator: the person or body responsible for weighing fishery products under Article 60(5) of Regulation 1224/2009, which may be the master.
• Weighing record: the per-landing record of weighed quantities, kept for three years.
• Verification scale interval (e): the value used to classify an instrument and express its maximum permissible errors.
• Maximum permissible error (MPE): the largest error allowed at a given load, set by class and load band.
• Notified body: a conformity assessment body designated by a Member State under the NAWI Directive or MID, such as NMi (number 0122).
• Verification: a conformity assessment that ends with a verification mark or certificate, as opposed to calibration, which quantifies errors.

How WPL approaches this

WPL Industries designs motion-compensated scales for fishing, offshore and research fleets, including the M2 bench scale, the M5 and M6 platform scales and the R50 Catch Label System, with WeightControl for logging every weighing. WPL holds NMi certificates EK-5417 and CE-284. The approval that a specific installation needs is set by the competent authority, so involve it early and ask WPL for the documentation relevant to your configuration.