How we assess fish stocks
The Fisheries Act 1996, Fisheries New Zealand's Harvest Strategy Standard (HSS) and several other official documents provide guidance on the performance measures used when assessing and managing fish stocks under the Quota Management System (QMS).
The Harvest Strategy Standard [PDF, 237 KB]
Each year, we convene many Stock Assessment Working Group meetings to assess the status of fish stocks using:
- scientific research (from contracted expert research providers)
- validated catch and fishing effort reports from commercial fisheries including electronic reporting
- data from our on-board observer programme
- other relevant information.
Stocks are assessed against 4 performance measures:
- A hard limit – a biomass level below which a stock is deemed to be collapsed and fishery closures should be considered to rebuild the stock at the fastest possible rate.
- A soft limit – a biomass level below which a stock is deemed to be overfished or depleted and needs to be actively rebuilt using a formal, time constrained rebuilding plan.
- A management target – the level of biomass or a fishing mortality rate that stocks are expected to fluctuate around for the best balance between use and sustainability, while allowing for environmental variation.
- Overfishing threshold – a rate of extraction (percentage of a stock removed each year) that should not be exceeded, as it will ultimately lead to stock biomass falling below other performance measures. Catching an optimal constant percentage of a stock each year means that catch tracks fluctuations in stock size, which is widely considered best practice.
The diagram below illustrates the relationship between the 4 performance measures. The trace of stock abundance is the result of fishing at the overfishing threshold. Stock abundance fluctuates around the management target and sometimes approaches the soft limit but never goes below this level and stays far above the hard limit. Management action to ensure the stock continues to fluctuate around the management target would normally be taken at all points where the stock dips too far below the target.
Performance measures and current stock status
All performance measures are important, but the key performance measure for determining the status of New Zealand’s fish stocks is the soft limit. A soft limit is a biomass level below which a stock is deemed to be overfished or depleted, resulting in potential sustainability concerns. We know the status of 152 stocks relative to the soft limit.
Most of our fish stocks of known status are in good shape (above the soft limit):
- 87.5% or 133 stocks and sub-stocks
- 97.3% of the total landings of assessed stocks by weight.
Of the 133 fish stocks that were above the soft limit in 2023, 109 (82%) were also at or above their management targets.
Summary overview of 2023 fish stock status [PDF, 1.2 MB]
2023 report on the status of New Zealand's fish stocks [PDF, 740 KB]
The 2023 stock status table shows the status of 401 of New Zealand's main fish stocks (or sub-stocks).
2023 stock status table [PDF, 389 KB]
A graphic summarising the information in the 2023 stock status table can be found below, noting that this only includes stocks for which all 4 performance measures are known.
Summary overview of 2023 fish stock status by performance measure [PDF, 251 KB]
Which stocks are included
Of the 401 fish stocks or sub-stocks included:
- 57 were assessed in 2023
- Numerous others have been assessed in previous years
- 396 are QMS stocks or sub-stocks
- 5 are non-QMS stocks or species that are Antarctic or highly migratory species.
Find out about catches and allowances for fish stocks
Nominal stocks not included
We haven't included 293 QMS fish stocks that:
- are in areas outside the main range of a species – set up for administrative purposes only
- have negligible catch or catch allowance (generally close to zero tonnes)
- have little to no potential to develop as recreational, customary or commercial fisheries.
List of nominal fish stocks [PDF, 203 KB]
Research helps set catch limits and other management controls
Fisheries New Zealand is serious about protecting New Zealand's fisheries. We carry out research on fish stocks regularly. It helps us make sure they're healthy and sustainable.
Technology allows scientists to accurately estimate the distribution and size of many fish populations. This research helps the Government set annual catch limits and other management measures to ensure fishers don't catch too much. If the research shows that fish numbers have grown, catch limits may be increased. If estimated fish numbers have decreased, then catch limits may be reduced and other management measures introduced.
Hoki: New Zealand's largest fishery
Overfished stocks in 2023
Nineteen (19) stocks or sub-stocks are below the soft limit, meaning they are overfished or depleted:
- 3 stocks of black cardinalfish
- 2 stocks or sub-stocks of dredge oysters
- 2 stocks or sub-stocks of orange roughy
- 2 stocks or sub-stocks of scallops
- 3 stocks or sub-stocks of tarakihi
- 1 stock or sub-stock each of pipi, school shark, stargazer and longfin eel
- Pacific bluefin tuna, southern bluefin tuna, and striped marlin, which are highly migratory species that are seasonally present in New Zealand waters and are managed by Regional Fisheries Management Organisations.
Rebuilding overfished stocks
We're managing fisheries on overfished stocks so that they will rebuild towards target levels, for example by:
- reducing total allowable commercial catches of stocks managed through the Quota Management System (QMS)
- supporting management of highly migratory species under international arrangements.
Tarakihi: a stock under a rebuilding plan
Reports for individual species
Each year, we publish a summary of all the available information on our fisheries and the status of each fish stock in 2 fisheries assessment plenary reports. The main report is published in May (3 volumes), and a second report for rock lobsters, oysters, scallops and highly migratory species (1 volume) is published in November.
- November 2023: Introduction section to yellowfin tuna [PDF, 17 MB]
- May 2023 Volume 1: Introductory sections and Alfonsino to Hoki [PDF, 16 MB]
- May 2023 Volume 2: Horse Mussel to Red Crab [PDF, 18 MB]
- May 2023 Volume 3: Red Gurnard to Yellow-eyed Mullet [PDF, 16 MB]
Who to contact
If you have questions about fish stock status, email info@mpi.govt.nz
