How we assess fish stocks
Fisheries New Zealand's Harvest Strategy Standard (HSS) provides guidance on the performance measures used when assessing and managing fish stocks under the 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 research providers)
- validated catch and fishing effort reports from commercial fisheries
- 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.
The diagram below illustrates the relationship between the four performance measures. The trace of stock abundance is the result of fishing just below 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 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 against the soft limit.
Most of our fish stocks of known status are in good shape (above the soft limit):
- 84.9% or 129 stocks and sub-stocks
- 94.3% of the total landings of assessed stocks by weight.
Of the 129 fish stocks that were above the soft limit in 2021, 102 (79.1%) were also at or above their management targets.
Summary overview of 2021 fish stock status [PDF, 334 KB]
2021 report on the status of New Zealand’s fish stocks [PDF, 785 KB]
The 'December 2021 stock status table' shows the status of 399 of New Zealand's main fish stocks (or sub-stocks).
2021 stock status table [PDF, 425 KB]
A graphic summarising the information in the 2021 stock status table can be found below, noting that this only includes stocks for which all 4 performance measures are known.
Summary overview of 2021 fish stock status by performance measure [PDF, 86 KB]
Which stocks are included
Of the 399 fish stocks or sub-stocks included:
- 50 were assessed in 2021
- Numerous others have been assessed in previous years
- 394 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 290 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, 27 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.
New Zealand's largest fishery: Hoki
Hoki (Macruronus novaezelandiae) are widely distributed throughout New Zealand waters from depths of 10 m to over 900 m, with the greatest abundance between 200–600 m. Hoki spawn from late June to mid-September, primarily on the west coast of the South Island (Hokitika Canyon) and in the Cook Strait, with smaller amounts of spawning found in the Puysegur area and in Pegasus Canyon. Hoki grow to a maximum size of 130 cm and maximum age of 20–25 years. They reach maturity between 3–5 years of age. The age of the commercial catch varies among areas, but most fish caught are between 3–12 years old.
The hoki fishery operates throughout the year and includes both spawning and non-spawning fisheries. In 2019-20 the overall hoki catch was 100,819 tonnes of which 35,131 tonnes (35%) was taken from the WCSI spawning fishery.
History of the hoki stock
The New Zealand hoki Quota Management Area (HOK 1) covers all New Zealand Exclusive Economic Zone waters except the Kermadecs and is managed to a target biomass range of 35–50% of the unfished mature biomass (B0). Stock status is assessed annually assuming two separate but interlinked stocks, eastern and western, with separate catch limits set for each stock through a voluntary catch split arrangement.
Both Fisheries New Zealand and hoki quota owners are aware that the western hoki stock has been declining somewhat in recent years. The reasons are unknown, but a similar although more extreme scenario happened in the early 2000’s – which no-one wants to repeat. The 2021 stock assessment estimated the biomass of the eastern stock to be near the upper bound of the management target range at 48% B0, whereas the biomass of the western stock was estimated to be at 35% B0, at the lower threshold of the management target range. Five-year projections using the 2020/21 catch limits estimated that the eastern stock biomass would remain within the top third of the management target range, while the western stock biomass was predicted to fall below the management target range.
Management measures
In response to recent stock assessment results, and following public consultation, catch limit reductions were made in both 2019 and 2021. The 2021 decision reduced the western catch limit by 10,000 tonnes, to 45,000 tonnes, and increased the eastern catch limit by 5,000 tonnes, to 65,000 tonnes for the 2021/22 fishing year, resulting in an overall catch limit reduction of 5,000 tonnes. Five-year projections under these catch limits predict both stocks to be in the management target range with the western stock projected to be at 37% B0 in 2026.
Hoki quota owners have been concerned about potential declines in the western hoki in recent years and have voluntarily agreed to shelve quota (i.e., to forego catch) even prior to the official TACC changes in 2019 and 2021. For example, the fishing industry:
- shelved 20,000 tonnes (plus carry forward) of western stock Annual Catch Entitlement (ACE) resulting in approximately 30,000 tonnes of HOK 1 ACE being transferred to a holding account that was not available for balancing against catch in the 2018/19 fishing year, and
- shelved 20,000 tonnes of HOK 1 ACE - 10,000 tonnes from each of the eastern and western stocks, creating an effective HOK 1 catch limit of 95,000 tonnes (western TACC = 45,000 tonnes) in the 2020/21 fishing year.
These measures have been developed in order to minimise and reverse the recent decline in the HOK 1 western stock biomass to ensure that the stock remains in good health and does not decline below the target range. In addition to the annual stock assessment and area catch limit, hoki are also managed using voluntary Hoki Operational Procedures consisting of:
- Hoki Seasonal Spawn Areas, which consist of week-long closures to hoki targeting in each of the main spawning areas during the spawning season, and
- Hoki Management Areas where vessel operators have agreed not to target hoki with vessels >28 metres within four areas where there is relatively high abundance of small hoki.
The way forward for hoki
The next stock assessment for hoki is scheduled for 2022 and will include new data from West Coast South Island and Chatham Rise trawl surveys, an acoustic survey from the Cook Strait and new information from the fishery including catch and effort data, age and length samples. This assessment will provide updated information on the status of the stock, which will inform consideration of any further amendments to the management settings required to manage the population within the management target range.
Overfished stocks in 2021
Twenty-three (23) 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
- 2 stocks or sub-stocks of snapper
- 3 stocks or sub-stocks of tarakihi
- 1 stock or sub-stock each of hake, John dory, pāua, pipi, school shark 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.
Rebuilding east coast tarakihi
Tarakihi, Nemadactylus macropterus, on the east coast of New Zealand appears to comprise a single biological stock. Tarakihi is a relatively long-lived species that reaches at least 40 years of age. Females mature at 6 years, after which they produce large numbers of pelagic (floating) eggs several times during each protracted summer/autumn spawning season. Following a 7 to 12 month pelagic phase, where the fertilised eggs, larvae and juvenile fish tend to remain in surface waters, east coast tarakihi mainly settle in nursery grounds off the east coast of the South Island, primarily the Canterbury Bight and Pegasus Bay. As they grow older, they move progressively further northward, with the highest proportions of older fish found off east Northland.
Research to monitor and rebuild tarakihi stocks
Stock assessments of east coast tarakihi are undertaken using a complex age-structured statistical model that accounts for gains and losses to the population, to provide an estimate of stock status in relation to the unfished level. The model is fitted to several sources of data, including annual landings, growth rates, age structure of trawl surveys, and commercial catches from different regions, indices of relative abundance based on trawl surveys and standardised commercial Catch per Unit of Effort (CPUE).
The first successful stock assessment for east coast tarakihi was completed in November 2017, and the assessment was updated in 2018, 2019, and in late 2021 (to be published in 2022).
TACC reductions were implemented based on the stock assessment results in 2018 and 2019. The TACC reductions are predicted to rebuild the east coast tarakihi stock to the management target in 25 years. In addition, a voluntary industry rebuilding plan is being implemented, which includes a number of additional measures:
- a move-on rule and research into mesh selectivity to avoid the capture of juvenile tarakihi
- voluntary closed areas
- limits on catches from the eastern parts of QMAs TAR1 and TAR7.
The way forward for east coast tarakihi
An updated stock assessment for east coast tarakihi was conducted in late 2021. This new assessment, including new information on the age composition of the commercial catch and results from new trawl surveys, provided information on the status of the stock, the response to previous management interventions, rebuild rates under current catch levels, and any further catch reductions required to rebuild the population within agreed time frames.
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.
Fisheries assessment plenary May 2021 – Volume 1: Introductory section and alfonsino to hake [PDF, 14 MB]
Fisheries assessment plenary May 2021 – Volume 2: Hoki to redbait [PDF, 14 MB]
Fisheries assessment plenary May 2021 – Volume 3: Red cod to yellow-eyed mullet [PDF, 14 MB]
Fisheries assessment plenary November 2021 – Introductory section to yellowfin tuna [PDF, 23 MB]
Who to contact
If you have questions about fish stock status, email info@mpi.govt.nz
