Conversion factors

Find conversion factors for different species, and learn how to use them. Read about your responsibilities using conversion factors, and vessel-specific conversion factors.


About conversion factors

Fishers and fish receivers use conversion factors to convert the processed weight of fish to the unprocessed weight (greenweight).

Why do fishers and fish receivers need them?

Fishers and licensed fish receivers (LFRs) need to report greenweight to meet their reporting requirements. To complete their LFR returns, LFRs must report the greenweight of fish they receive from fishers. LFRs must do this even if the fish arrive processed.

Fishers must also report the greenweight of their catch for their landing return. To do that, they need the information from LFRs.

How conversion factors work

Because many commercial fishers process their catch at sea, LFRs often receive the processed weight. But using conversion factors, they can work out the unprocessed weight of fish that arrive already processed, meaning they can report accurately.

The conversion factors for a specific species depends on how much the fish is processed. The more that's removed from the fish, the higher the conversion factor. If used as intended, conversion factors provide all vessels that process fish at sea with a consistent and fair catch reporting process.

Find a conversion factor

FishServe – MPI's partner for administering commercial fishing – has a conversion factor tool on its website.

To use that tool, you'll need to know the species code for the fish you're working with.

Using conversion factors

To calculate the greenweight of processed fish, multiply the weight of processed fish by the conversion factor for the species in that processed state. In cases where fish are landed in 2 or more processed states, use the conversion factor for the one that weighs the most.

You can also find conversion factors in the Fisheries (Conversion Factors) Notice 2014. It provides:

  • conversion factors for different species in different processed states
  • descriptions and diagrams of processed states (starting on page 12).

Remember – MPI may review and change conversion factors each year.

Your responsibilities

Fisher responsibilities

Permit holders need to use the greenweight information provided by the LFR to complete landing returns.

Licensed fish receiver responsibilities

LFRs must provide fishers with documents that help record the species, landed state, and greenweight of fish.

Vessel operator responsibilities

Vessel operators should ensure that vessel production specifications comply with the most current conversion factors notice.

Vessel operators should also ensure that vessels monitor all production to ensure compliance with conversion factor requirements. They should place emphasis on:

  • head cuts (and the inclusion or exclusion of fins)
  • the placement of any tail cuts (especially where there are specifications relating to tail removal)
  • making sure fillet products meet processed state definitions
  • making sure the processed state matches the conversion factor.

So that fishers know what they have to do, vessels that process at sea should have on board:

  • a list of current conversion factors – for all species/processed state combinations produced at sea
  • copies of the current processed state definitions, and diagrams relevant to all processed states produced at sea (currently contained in the notice). Factory managers and processing staff should be able to access the definitions and diagrams.

Find out more in our factsheet: Conversion factors [PDF, 583 KB]

Vessel-specific conversion factors

If a vessel operator believes they can obtain a higher yield for a specific species/processed state combination, they can apply to MPI for a vessel-specific conversion factor certificate. MPI will only issue one after observers have completed at least one sampling trip on the vessel.

Once MPI has issued a vessel-specific conversion factor certificate, observers will need to do some conversion factor sampling whenever they're on the vessel.

MPI also does an annual review.

Observer fees are normally covered through cost recovery levies – but charges apply for the part of any trip where vessel-specific conversion factor sampling is done. To calculate this, observers will estimate how much time they spend sampling during a trip. That portion is then direct-charged – the rest of the daily observer fee is covered under the annual sea days plan.

How we calculate conversion factors

The conversion factors listed in the Fisheries (Conversion Factors) Notice 2014 are based on information collected by MPI observers. They are averaged across:

  • geographic areas
  • vessel types.

The factors can change each year.

Who to contact

If you need more information on conversion factors, email fisheries@mpi.govt.nz

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